Antenna gain block for the Hv band. HF amateur antennas

Shortwave antennas
Practical amateur radio antenna designs

This section presents a large number of different practical antenna designs and other related devices. To facilitate the search, you can use the button "View a list of all published antennas". More on the topic - see the CATEGORY with a regular replenishment of new publications in the subheading.

Off-center dipole

Many shortwave operators are interested in simple HF antennas that provide operation without any switching on several amateur bands. The most famous of these antennas is the Windom with a single-wire feeder. But the payment for the simplicity of the manufacture of this antenna was and remains the inevitable interference with television and radio broadcasting when powered by a single-wire feeder and the accompanying clarification of relations with neighbors.

The idea of ​​Windom-dipoles seems to be simple. By shifting the feed point from the center of the dipole, you can find a ratio of the lengths of the arms at which the input resistances on several ranges become quite close. Most often, they are looking for dimensions at which it is close to 200 or 300 Ohm, and matching with low-impedance power cables is carried out using balun transformers (BALUN) with a transformation ratio of 1: 4 or 1: 6 (for a cable with a characteristic impedance of 50 Ohm). This is how, for example, the antennas FD-3 and FD-4 are made, which are produced, in particular, in series in Germany.

Radio amateurs design similar antennas on their own. Certain difficulties, however, arise in the manufacture of balancing transformers, in particular, for operation in the entire short-wavelength range and when using power exceeding 100 W.

A more serious problem is that such transformers normally only operate on a matched load. And this condition is obviously not met in this case - the input impedance of such antennas is really close to the required values ​​of 200 or 300, but obviously differs from them, and on all ranges. The consequence of this is that to some extent this design retains the antenna effect of the feeder despite the use of a matching transformer and a coaxial cable. As a result, the use of balun transformers in these antennas, even of a rather complex design, does not always completely solve the TVI problem.

Aleksandr Shevelev (DL1BPD) succeeded, using line matching devices, to develop a version of Windom-dipole matching, which use power through a coaxial cable and are devoid of this drawback. They were described in the magazine “Radio amateur. Bulletin SRR "(2005, March, pp. 21, 22).

Calculations show that the best result is obtained when using lines with characteristic impedances of 600 and 75 ohms. A line with a characteristic impedance of 600 ohms adjusts the input impedance of the antenna on all operating ranges to a value of approximately 110 ohms, and a 75 ohm line transforms this impedance to a value close to 50 ohms.

Let's consider a variant of such a Windom-dipole (ranges of 40-20-10 meters). In fig. 1 shows the lengths of the arms and dipole lines on these ranges for a wire with a diameter of 1.6 mm. The total length of the antenna is 19.9 m. When using an insulated antenna cord, the arm lengths are made slightly shorter. A line with a characteristic impedance of 600 ohms and a length of approximately 1.15 meters is connected to it, and a coaxial cable with a characteristic impedance of 75 ohms is connected to the end of this line.

The latter, with a cable shortening factor equal to K = 0.66, has a length of 9.35 m. The reduced line length with a characteristic impedance of 600 ohms corresponds to a shortening factor K = 0.95. With such dimensions, the antenna is optimized for operation in the frequency bands 7 ... 7.3 MHz, 14 ... 14.35 MHz and 28 ... 29 MHz (with a minimum SWR at a frequency of 28.5 MHz). The calculated SWR graph of this antenna for an installation height of 10 m is shown in Fig. 2.

Using a cable with a characteristic impedance of 75 ohms is generally not the best option in this case. Lower VSWR values ​​can be obtained using a cable with a characteristic impedance of 93 ohms or a line with a characteristic impedance of 100 ohms. It can be made from a coaxial cable with a characteristic impedance of 50 Ohm (for example, http://dx.ardi.lv/Cables.html). If a line with a characteristic impedance of 100 Ohm from a cable is used, it is advisable to turn on BALUN 1: 1 at its end.

To reduce the level of interference from the part of the cable with a characteristic impedance of 75 Ohm, a choke should be made - a coil (coil) Ø 15-20 cm, containing 8-10 turns.

The directional pattern of this antenna practically does not differ from the directional pattern of a similar Windom-dipole with a balun. Its efficiency should be slightly higher than that of antennas using BALUN, and tuning should be no more difficult than tuning conventional Windom dipoles.

Vertical dipole

It is well known that for long-distance operation a vertical antenna has an advantage, since its directional pattern in the horizontal plane is circular, and the main lobe of the pattern in the vertical plane is pressed to the horizon and has a low level of radiation to the zenith.

However, the manufacture of a vertical antenna is associated with a number of design problems. The use of aluminum pipes as a vibrator and the need for its efficient operation to install at the base of the "vertical" a system of "radials" (counterweights), consisting of a large number of wires with a length of a quarter wave. If you use not a pipe, but a wire as a vibrator, the mast supporting it must be made of a dielectric and all the guy wires supporting the dielectric mast must also be dielectric, or be broken into non-resonant sections by insulators. All this is associated with costs and often constructively impracticable, for example, due to the lack of the necessary area for placing the antenna. Do not forget that the input impedance of the "verticals" is usually below 50 Ohm, and this will also require its coordination with the feeder.

On the other hand, horizontal dipole antennas, which include Inverted V antennas, are structurally very simple and cheap, which explains their popularity. The vibrators of such antennas can be made of almost any wire, and the masts for their installation can also be made of any material. The input impedance of the horizontal dipoles or Inverted V is close to 50 ohms, and it is often possible to do without additional termination. The directional patterns of the Inverted V antenna are shown in Fig. one.

The disadvantages of horizontal dipoles include their non-circular radiation pattern in the horizontal plane and a large radiation angle in the vertical plane, which is generally acceptable for operation on short paths.

Turn the usual horizontal wire dipole vertically by 90 degrees. and we get a vertical full-size dipole. To reduce its length (in this case, the height), we use the well-known solution - "dipole with bent ends". For example, a description of such an antenna is in the files of the library of I. Goncharenko (DL2KQ) for the MMANA-GAL program - AntShortCurvedCurved dipole.maa. By bending back some of the vibrators, we, of course, lose some in the antenna gain, but we significantly gain in the required mast height. The bent ends of the vibrators should be located one above the other, while the radiation of vibrations with horizontal polarization, which is harmful in our case, is compensated. A sketch of the proposed version of the antenna, called by the authors Curved Vertical Dipole (CVD), is shown in Fig. 2.

Initial conditions: a dielectric mast 6 m high (fiberglass or dry wood), the ends of the vibrators are pulled by a dielectric cord (fishing line or nylon) at a slight angle to the horizon. The vibrator is made of copper wire with a diameter of 1 ... 2 mm, bare or insulated. At the break points, the vibrator wire is attached to the mast.

If we compare the calculated parameters of the Inverted V and CVD antennas for the 14 MHz range, it is easy to see that due to the shortening of the radiating part of the dipole, the CVD antenna has 5 dB less gain, however, at a radiation angle of 24 degrees. (CVD maximum gain) the difference is only 1.6 dB. In addition, the Inverted V antenna has a horizontal irregularity of up to 0.7 dB, i.e. in some directions it outperforms CVD in gain by only 1 dB. Since the calculated parameters of both antennas turned out to be close, the final conclusion could only be made by experimental verification of CVD and practical work on the air. Three CVD antennas were manufactured for the 14, 18 and 28 MHz bands according to the dimensions shown in the table. They all had the same design (see Fig. 2). The sizes of the upper and lower arms of the dipole are the same. Our vibrators were made of P-274 field telephone cable, insulators were made of plexiglass. The antennas were lifted onto a 6 m high fiberglass mast, with the top of each antenna being 6 m above the ground. The bent parts of the vibrators were pulled back with a nylon cord at an angle of 20-30 degrees. to the horizon, since we did not have tall items for fastening the guy wires. The authors made sure (this was also confirmed by modeling) that the deviation of the bent sections of the vibrators from the horizontal position by 20-30 degrees. practically does not affect the characteristics of the CVD.

Simulations in the MMANA software show that such a curved vertical dipole easily matches a 50 ohm coaxial cable. It has a small angle of radiation in the vertical plane and a circular radiation pattern in the horizontal plane (Fig. 3).

The design simplicity made it possible to change one antenna to another within five minutes, even in the dark. The same coaxial cable was used to power all CVD antenna variants. He approached the vibrator at an angle of about 45 degrees. To suppress the common-mode current, a tubular ferrite magnetic circuit (filter-latch) is installed on the cable near the connection point. It is advisable to install several similar magnetic circuits on a 2 ... 3 m long cable section close to the antenna web.

Since the antennas were made of vole, its insulation increased the electrical length by about 1%. Therefore, antennas made according to the dimensions given in the table needed some shortening. The adjustment was carried out by adjusting the length of the lower bent section of the vibrator, easily accessible from the ground. By folding part of the length of the lower bent wire in two, you can fine-tune the resonant frequency by moving the end of the bent section along the wire (a kind of trimming loop).

The resonant frequency of the antennas was measured with an MF-269 antenna analyzer. All antennas had a clearly defined SWR minimum in the limits of the amateur bands, not exceeding 1.5. For example, a 14 MHz antenna had a minimum SWR at a frequency of 14155 kHz of 1.1, and a bandwidth of 310 kHz for a SWR of 1.5 and 800 kHz for a SWR of 2.

For comparative tests, an Inverted V of the 14 MHz band was used, mounted on a metal mast with a height of 6 m. The ends of the vibrators were at a height of 2.5 m above the ground.

To obtain objective estimates of the signal level in QSB conditions, the antennas were repeatedly switched from one to another with a switching time of no more than one second.

table

Radio communications were carried out in SSB mode with a transmitter power of 100 W on routes ranging from 80 to 4600 km. On the 14 MHz band, for example, all correspondents who were at a distance of more than 1000 km noted that the signal level with the CVD antenna was one or two points higher than with the Inverted V. At a distance of less than 1000 km, Inverted V had some minimal advantage. ...

These tests were carried out during a period of relatively poor conditions for the passage of radio waves on the HF bands, which explains the lack of more distant communications.

During the absence of ionospheric propagation in the 28 MHz range, we conducted several surface wave radio communications from our QTH with this antenna with Moscow shortwave wavelengths at a distance of about 80 km. On a horizontal dipole, even raised slightly above the CVD antenna, none of them could be heard.

The antenna is made from cheap materials and does not require a lot of space for placement.

When used as guy lines, nylon fishing line, it may well disguise itself as a flagpole (a cable divided into sections of 1.5 ... 3 m by ferrite chokes, while it can go along or inside the mast and be unobtrusive), which is especially valuable with unfriendly neighbors in the country (fig. 4).

Files in the .maa format for independent study of the properties of the described antennas are located.

Vladislav Shcherbakov (RU3ARJ), Sergey Filippov (RW3ACQ),

Moscow city

A modification of the T2FD antenna known to many has been proposed, which allows covering the entire range of radio amateur HF frequencies, losing quite a bit to a half-wave dipole in the 160 meter range (0.5 dB on near and about 1.0 dB on DX paths).
With an exact repetition, the antenna starts working immediately and does not need tuning. The peculiarity of the antenna is noticed: static interference is not perceived, and in comparison with the classical half-wave dipole. In this performance, the reception of the broadcast turns out to be quite comfortable. Very weak DX stations are normally listened to, especially in the low frequency ranges.

Long-term operation of the antenna (more than 8 years) allowed it to be deservedly attributed to low-noise receiving antennas. Otherwise, in terms of efficiency, this antenna is practically not inferior to a band half-wave dipole or Inverted Vee on any of the bands from 3.5 to 28 MHz.

And one more observation (based on feedback from distant correspondents) - there are no deep QSBs during the communication. Of the 23 modifications of this antenna produced, the one proposed here deserves special attention and can be recommended for massive repetition. All proposed dimensions of the antenna-feeder system are calculated and precisely verified in practice.

Antenna strip

The vibrator dimensions are shown in the figure. The halves (both) of the vibrator are symmetrical, the extra length of the "inner corner" is cut in place, and a small platform (always insulated) is also attached there to connect to the supply line. Ballast resistor 240 Ohm, foil (green), rated for 10 W. You can also use any other resistor of the same power, the main thing is that the resistance must be non-inductive. Copper wire - insulated, with a cross section of 2.5 mm. Spacers - wooden slats in a section with a section of 1 x 1 cm, varnished. The distance between the holes is 87 cm. We use a nylon cord on the stretch marks.

Overhead power line

For the power line, we use a PV-1 copper wire with a cross section of 1 mm, vinyl plastic spacers. The distance between the conductors is 7.5 cm. The length of the entire line is 11 meters.

Author's installation option

A metal, bottom-grounded, mast is used. The mast is installed on a 5-storey building. Mast - 8 meters from a pipe Ø 50 mm. The ends of the antenna are placed 2 m from the roof. The core of the matching transformer (SHPTR) is made of the TVS-90LTs5 line transformer. The coils are removed there, the core itself is glued with Supermoment glue to a solid state and with three layers of varnished cloth.

Winding is made in 2 wires without twisting. The transformer contains 16 turns of a single-core insulated copper wire Ø 1 mm. The transformer has a square (sometimes rectangular) shape, so 4 pairs of turns are wound on each of the 4 sides - the best version of the current distribution.

VSWR in the entire range is from 1.1 to 1.4. ShPTR is placed in a tin screen, well soldered with a braid of the feeder. From the inside, the middle terminal of the transformer winding is reliably soldered to it.

After assembly and installation, the antenna will work immediately and in almost any conditions, that is, located low above the ground or above the roof of the house. She has a very low level of TVI (television interference), and this may additionally interest radio amateurs working from villages or summer residents.

Antenna Loop Feed Array Yagi 50 MHz

Antennas Yagi (Yagi) with a loop vibrator located in the plane of the antenna are called LFA Yagi (Loop Feed Array Yagi) and are characterized by a wider operating frequency range than conventional Yagi. One of the popular Yagi LFAs is Justin Johnson's 5-piece construction (G3KSC) for the 6-meter range.

Antenna layout, distances between elements and dimensions of elements are shown in the table below and in the drawing.

The dimensions of the elements, the distances to the reflector and the diameters of the aluminum tubes from which the elements are made according to the table: The elements are installed on a traverse with a length of about 4.3 m from a square aluminum profile with a cross section of 90 × 30 mm through insulating transition strips. The vibrator is powered by a 50 ohm coaxial cable through a balun 1:1.

Antenna tuning for the minimum SWR in the middle of the range is performed by adjusting the position of the end U-shaped parts of the vibrator from tubes with a diameter of 10 mm. It is necessary to change the position of these inserts symmetrically, that is, if the right insert is pushed out by 1 cm, then the left one must be pushed out by the same amount.

SWR meter on strip lines

SWR meters, widely known from the amateur radio literature, are made using directional couplers and are single-layer coil or ferrite ring core with multiple turns of wire. These devices have a number of disadvantages, the main of which is that when measuring high powers, a high-frequency "pickup" appears in the measuring circuit, which requires additional costs and efforts to screen the detector part of the SWR meter to reduce the measurement error, and with the formal attitude of the radio amateur to manufacturing instrument, the SWR meter can cause the impedance of the feed line to change depending on the frequency. The offered SWR meter based on strip-line directional couplers is free from such disadvantages, it is designed as a separate independent device and allows you to determine the ratio of direct and reflected waves in the antenna circuit with an input power of up to 200 W in a frequency range of 1 ... 50 MHz with a characteristic impedance of a feeder line 50 Ohm. If you only need an indicator of the transmitter output power or monitor the antenna current, you can use the following device: When measuring SWR in lines with a characteristic impedance other than 50 Ohm, the values ​​of the resistors R1 and R2 should be changed to the value of the characteristic impedance of the line being measured.

SWR meter design

The SWR meter is made on a 2 mm thick double-sided foil-clad PTFE board. As a replacement, it is possible to use double-sided fiberglass.

L2 line is made on the back side of the board and is shown with a dashed line. Its dimensions are 11 × 70 mm. Caps are inserted into the holes of line L2 for connectors XS1 and XS2, which are flared and soldered together with L2. The common bus on both sides of the board has the same configuration and is shaded in the board diagram. In the corners of the board, holes are drilled into which pieces of wire with a diameter of 2 mm are inserted, soldered on both sides of the common bus. Lines L1 and L3 are located on the front side of the board and have dimensions: straight section 2 × 20 mm, distance between them is 4 mm and are located symmetrically to the longitudinal axis of line L2. The displacement between them along the longitudinal axis L2 is 10 mm. All radioelements are located on the side of the L1 and L2 strip lines and are soldered overlapping directly to the printed conductors of the SWR meter board. The printed conductors of the board should be silver-plated. The assembled board is soldered directly to the contacts of the XS1 and XS2 connectors. The use of additional connecting leads or coaxial cable is not permitted. The finished SWR meter is placed in a non-magnetic box 3 ... 4 mm thick. The common bus of the SWR meter board, the device body and connectors are electrically connected to each other. The SWR is counted as follows: in the S1 "Straight" position, using R3, set the microammeter needle to the maximum value (100 μA) and turning S1 into "Reverse", the SWR value is measured. In this case, the reading of the device 0 µA corresponds to VSWR 1; 10 μA - VSWR 1.22; 20 μA - VSWR 1.5; 30 μA - VSWR 1.85; 40 μA - VSWR 2.33; 50 μA - VSWR 3; 60 μA - VSWR 4; 70 μA - VSWR 5.67; 80 μA - 9; 90 μA - VSWR 19.

HF Nine Band Antenna

The antenna is a variation of the well-known "WINDOM" multi-band antenna, in which the feed point is off-center. In this case, the input impedance of the antenna in several amateur KB bands is approximately 300 ohms,
which makes it possible to use both a single wire and a two-wire line with a corresponding characteristic impedance as a feeder, and, finally, a coaxial cable connected through a matching transformer. In order for the antenna to work in all nine amateur KB bands (1.8; 3.5; 7; 10; 14; 18; 21; 24 and 28 MHz), essentially two WINDOM antennas are connected in parallel (see above Fig. a): one with a total length of about 78 m (l / 2 for the 1.8 MHz band), and the other with a total length of about 14 m (l / 2 for the 10 MHz band and l for the 21 MHz band). Both emitters are powered by a single coaxial cable with a characteristic impedance of 50 ohms. The matching transformer has a resistance transformation ratio of 1: 6.

The approximate location of the antenna radiators in plan is shown in Fig. b.

When the antenna was installed at a height of 8 m above a well-conducting "ground", the standing wave ratio in the 1.8 MHz range did not exceed 1.3, in the 3.5, 14.21, 24 and 28 MHz ranges - 1.5, in the 7.10 and 18 ranges. MHz - 1.2. In the 1.8, 3.5 MHz bands, and to some extent in the 7 MHz band with a suspension height of 8 m, the dipole is known to radiate mainly at large angles to the horizon. Consequently, in this case, the antenna will be effective only when conducting short-range communications (up to 1500 km).

The diagram for connecting the windings of the matching transformer to obtain a transformation ratio of 1: 6 is shown in Fig. C.

Windings I and II have the same number of turns (as in a conventional transformer with a transformation ratio of 1: 4). If the total number of turns of these windings (and it depends primarily on the size of the magnetic circuit and its initial magnetic permeability) is equal to n1, then the number of turns n2 from the junction point of windings I and II to the tap is calculated by the formula n2 = 0.82n1.t

Horizontal bezels are popular. Rick Rogers (KI8GX) experimented with a "ramp" attached to a single mast.

To install the "inclined frame" variant with a perimeter of 41.5 m, a mast with a height of 10 ... 12 meters and an auxiliary support with a height of about two meters are required. Opposite corners of the frame, which is in the shape of a square, are attached to these masts. The distance between the masts is chosen so that the angle of inclination of the frame in relation to the ground is within 30 ... 45 °. The feeding point of the frame is located in the upper corner of the square. The frame is powered by a coaxial cable with a characteristic impedance of 50 Ohm. According to the KI8GX measurements in this version, the frame had a SWR = 1.2 (minimum) at 7200 kHz, SWR = 1.5 (rather "dull" minimum) at frequencies above 14100 kHz, SWR = 2.3 over the entire 21 MHz range, SWR = 1.5 (minimum) at 28400 kHz. At the edges of the ranges, the VSWR value did not exceed 2.5. According to the author, a slight increase in the length of the frame will shift the minima closer to the telegraph sections and will make it possible to obtain VSWR less than 2 within all operating ranges (except for 21 MHz).

QST # 4 2002

Vertical antenna at 10, 15 meters

A simple combined vertical antenna for 10 and 15 m bands can be made both for work in stationary conditions and for out-of-town trips. The antenna is a vertical radiator (Fig. 1) with a blocking filter (ladder) and two resonant counterweights. The trap is tuned to the selected frequency in the range of 10 m, therefore in this range the element L1 is the emitter (see figure). In the range of 15 m, the inductance coil of the ladder is lengthening and, together with the L2 element (see figure), brings the total length of the radiator to 1/4 of the wavelength in the 15 m range. antenna) mounted on fiberglass tubes. A "trap" antenna is less "capricious" in setting up and operating than an antenna consisting of two adjacent radiators. Antenna dimensions are shown in Fig.2. The emitter consists of several sections of duralumin pipes of different diameters, connected to one another through adapter sleeves. The antenna is powered by a 50-ohm coaxial cable. To prevent the flow of HF current along the outer side of the cable sheath, power is supplied through a current balun (Fig. 3), made on the FT140-77 ring core. The winding consists of four turns of RG174 coaxial cable. The dielectric strength of this cable is sufficient for operation with a transmitter with an output power of up to 150 W. When working with a more powerful transmitter, either a Teflon-insulated cable (eg RG188) or a large diameter cable should be used, which naturally requires an appropriately sized ferrite ring. The balun is installed in a suitable dielectric box:

It is recommended that a 33 kΩ non-inductive two-watt resistor be installed between the vertical radiator and the support pipe on which the antenna is mounted to prevent static build-up on the antenna. It is convenient to place the resistor in the box in which the balun is installed. The design of the ladder can be of any kind.
So, the inductor can be wound on a piece of PVC pipe with a diameter of 25 mm and a wall thickness of 2.3 mm (the lower and upper parts of the radiator are inserted into this pipe). The coil contains 7 turns of copper wire with a diameter of 1.5 mm in varnish insulation, wound with a pitch of 1-2 mm. The required inductance of the coil is 1.16 μH. A high-voltage (6 kV) ceramic capacitor with a capacity of 27 pF is connected in parallel to the coil, and the result is a parallel oscillatory circuit at a frequency of 28.4 MHz.

Fine tuning of the resonant frequency of the circuit is carried out by compressing or stretching the turns of the coil. After tuning, the turns are fixed with glue, but it should be borne in mind that an excessive amount of glue applied to the coil can significantly change its inductance and lead to an increase in dielectric losses and, accordingly, a decrease in the antenna efficiency. In addition, the ladder can be made from a coaxial cable by winding 5 turns on a 20 mm PVC pipe, but it is necessary to provide for the possibility of changing the winding pitch to ensure accurate tuning to the required resonant frequency. The design of the trap for its calculation is very convenient to use the Coax Trap program, which can be downloaded from the Internet.

Practice shows that such traps work reliably with 100-watt transceivers. To protect the drain from the environment, it is placed in a plastic pipe, which is closed with a plug on top. Counterweights can be made from bare wire 1 mm in diameter and should be spaced as far apart as possible. If a wire in plastic insulation is used for counterweights, then they should be somewhat shortened. So, counterweights made of copper wire with a diameter of 1.2 mm in vinyl insulation with a thickness of 0.5 mm should have a length of 2.5 and 3.43 m for the ranges of 10 and 15 m, respectively.

The tuning of the antenna begins in the range of 10 m, after making sure that the trap is tuned to the selected resonant frequency (for example, 28.4 MHz). The minimum SWR in the feeder is achieved by changing the length of the lower (up to the ladder) part of the emitter. If this procedure is unsuccessful, then it will be necessary to change within small limits the angle at which the counterweight is located relative to the emitter, the length of the counterweight and, possibly, its location in space. ) parts of the emitter achieve a minimum SWR. If it is impossible to achieve an acceptable SWR, then the solutions recommended for tuning the antenna in the 10 m range should be applied. In the prototype antenna in the 28.0-29.0 and 21.0-29.45 MHz frequency bands, the SWR did not exceed 1.5.

Tuning Antennas and Loops Using a Jammer

Any type of relay with an appropriate supply voltage and with a normally closed contact can be used to operate this jammer circuit. In this case, the higher the relay supply voltage, the higher the level of noise generated by the generator. To reduce the level of interference to the tested devices, it is necessary to carefully shield the generator, and supply power from a battery or accumulator to prevent interference from entering the network. In addition to setting up noise-immune devices, with such a noise generator, you can measure and set up high-frequency equipment and its components.

Determination of the resonant frequency of the circuits and the resonant frequency of the antenna

When using a survey receiver with a continuous range or wavemeter, you can determine the resonant frequency of the circuit under test from the maximum noise level at the output of the receiver or wavemeter. To eliminate the influence of the generator and receiver on the parameters of the measured circuit, their communication coils should have the minimum possible connection with the circuit.When connecting the interference generator to the tested antenna WA1, it is possible to determine its resonant frequency or frequencies in the same way as measuring the circuit.

I. Grigorov, RK3ZK

T2FD wideband aperiodic antenna

Due to the large linear dimensions, the construction of antennas at low frequencies causes quite certain difficulties for radio amateurs due to the lack of space necessary for these purposes, the complexity of manufacturing and installing high masts. Therefore, working on surrogate antennas, many use interesting low-frequency bands mainly for local connections with an amplifier “one hundred watts per kilometer”.

In the radio amateur literature, there are descriptions of rather effective vertical antennas, which, according to the authors, "practically do not occupy the area." But it is worth remembering that significant space is required to accommodate the counterweight system (without which the vertical antenna is ineffective). Therefore, in terms of the occupied area, it is more advantageous to use linear antennas, especially those made according to the popular "inverted V" type, since only one mast is required for their construction. However, the transformation of such an antenna into a dual-band antenna greatly increases the occupied area, since it is desirable to place radiators of different ranges in different planes.

Attempts to use switchable extension elements, tuned power lines and other methods of converting a piece of wire into an all-band antenna (with available suspension heights of 12-20 meters) most often lead to the creation of "super surrogates" by tuning that you can conduct amazing tests of your nervous system.

The proposed antenna is not "super efficient", but it allows you to work normally in two or three bands without any switching, is characterized by relative stability of parameters and does not need painstaking tuning. With a high input impedance at low suspension heights, it provides better efficiency than simple wire antennas. This is a somewhat modified widely known T2FD antenna, popular in the late 60s, unfortunately, almost never used today. Obviously, it fell into the category of "forgotten" because of the absorbing resistor, which dissipates up to 35% of the transmitter power. Fearing to lose these percentages, many consider the T2FD to be a frivolous design, although they calmly use a pin with three counterweights on the HF bands, efficiency. which does not always "hold out" to 30%. I had to hear a lot of "cons" in relation to the proposed antenna, often unreasonable. I will try to summarize the pros, thanks to which the T2FD was chosen to work on the low bands.

In an aperiodic antenna, which in its simplest form is a conductor with a characteristic impedance Z, loaded on an absorbing resistance Rh = Z, the incident wave, having reached the load Rh, is not reflected, but is completely absorbed. Due to this, the traveling wave mode is established, which is characterized by the constancy of the maximum value of the current Imax along the entire conductor. In fig. 1 (A) shows the current distribution along the half-wave vibrator, and Fig. 1 (B) - along the traveling wave antenna (radiation losses and in the antenna conductor are not conventionally taken into account. The shaded area is called the current area and is used to compare simple wire antennas.

In the theory of antennas, there is the concept of the effective (electrical) length of the antenna, which is determined by the replacement of a real vibrator by an imaginary one, along which the current is distributed evenly, having the same value of Imax,
as in the investigated vibrator (ie, the same as in Fig. 1 (B)). The length of the imaginary vibrator is chosen such that the geometric area of ​​the current of the real vibrator is equal to the geometric area of ​​the imaginary one. For a half-wave vibrator, the length of the imaginary vibrator, at which the current areas are equal, is equal to L / 3.14 [pi], where L is the wavelength in meters. It is not difficult to calculate that the length of a half-wave dipole with geometric dimensions = 42 m (3.5 MHz range) is electrically equal to 26 meters, which is the effective length of the dipole. Returning to fig. 1 (B), it is easy to find that the effective length of the aperiodic antenna is practically equal to its geometric length.

The experiments carried out in the 3.5 MHz range allow us to recommend this antenna to radio amateurs as a good cost-benefit option. An important advantage of the T2FD is its broadband and operability at "ridiculous" suspension heights for low frequency ranges, starting from 12-15 meters. For example, a dipole of the 80-meter range with such a suspension height turns into a "military" anti-aircraft antenna,
since radiates upward about 80% of the supplied power. The main dimensions and design of the antenna are shown in Fig. 2, In Fig. 3 - the upper part of the mast, where the balancing transformer T and the absorbing resistance R are installed The transformer design in Fig. 4

The transformer can be made on almost any magnetic circuit with a permeability of 600-2000 NN. For example, a core from TVS of tube TVs or a pair of rings stacked together with a diameter of 32-36 mm. It contains three windings, wound in two wires, for example MGTF-0.75 sq. Mm (used by the author). The cross section depends on the power supplied to the antenna. The wires of the windings are laid tightly, without steps and twists. Cross the wires at the location shown in Figure 4.

It is enough to wind 6-12 turns in each winding. If you carefully consider Fig. 4, then the manufacture of the transformer does not cause any difficulties. The core should be protected against corrosion with varnish, preferably with oil or moisture resistant glue. The absorption resistance should theoretically dissipate 35% of the input power. It has been experimentally established that MLT-2 resistors withstand 5-6-fold overloads in the absence of direct current at frequencies of the KB ranges. With a power of 200 W, 15-18 MLT-2 resistors connected in parallel are sufficient. The resulting resistance should be between 360-390 ohms. With the dimensions shown in Fig. 2, the antenna operates in the 3.5-14 MHz ranges.

For operation in the 1.8 MHz range, it is desirable to increase the total antenna length to at least 35 meters, ideally 50-56 meters. With the correct implementation of the transformer T, the antenna does not need any tuning, you just need to make sure that the SWR is in the range of 1.2-1.5. Otherwise, the error should be looked for in the transformer. It should be noted that with the popular 4: 1 transformer based on a long line (one winding in two wires), the antenna performance deteriorates sharply, and the VSWR can be 1.2-1.3.

German Quad Antenna at 80, 40, 20, 15, 10 and even 2 m

Most urban radio amateurs face the problem of shortwave antenna placement due to the limited space.

But if there is a place for hanging a wire antenna, then the author suggests using it and making "GERMAN Quad / images / book / antenna". He reports that she works well on 6 amateur bands 80, 40, 20, 15, 10 and even 2 meters. The diagram of the antenna is shown in the figure. To make it, you will need exactly 83 meters of copper wire with a diameter of 2.5 mm. The antenna is a 20.7 meter square that hangs horizontally at a height of 30 feet - about 9 meters. The connecting line is made of 75 ohm coaxial cable. According to the author, the antenna has a gain of 6 dB with respect to the dipole. At 80 meters it has rather high angles of radiation and works well at distances of 700 ... 800 km. Beginning in the 40m range, the angles of emission in the vertical plane decrease. On the horizon, the antenna does not have any directivity priorities. Its author proposes to use it for mobile-stationary work in the field.

3/4 Long Wire antenna

Most of its dipole antennas are based on 3 / 4L wavelengths on either side. We will consider one of them - "Inverted Vee".
The physical length of the antenna is greater than its resonant frequency, increasing the length to 3 / 4L expands the antenna bandwidth compared to a standard dipole and lowers the vertical radiation angles, making the antenna more long-range. In the case of a horizontal arrangement in the form of an angular antenna (half-bomb), it acquires very decent directional properties. All these properties apply to the antenna made in the form of "INV Vee". The antenna input impedance is reduced and special measures are required to match the power line. With a horizontal suspension and a total length of 3 / 2L, the antenna has four main and two minor lobes. The author of the antenna (W3FQJ) provides many calculations and diagrams for different dipole arm lengths and suspension hauls. According to him, he deduced two formulas containing two "magic" numbers, allowing you to determine the length of the dipole arm (in feet) and the length of the feeder in relation to the amateur bands:

L (each half) = 738 / F (in MHz) (in feet feet),
L (feeder) = 650 / F (in MHz) (in feet feet).

For a frequency of 14.2 MHz,
L (each half) = 738 / 14.2 = 52 feet (feet),
L (feeder) = 650 / F = 45 feet 9 inches.
(Conduct the conversion to the metric system yourself, the author of the antenna counts everything in feet). 1 Feet = 30.48 cm

Then for a frequency of 14.2 MHz: L (each half) = (738 / 14.2) * 0.3048 = 15.84 meters, L (feeder) = (650 / F14.2) * 0.3048 = 13.92 meters

P.S. For other selected arm length ratios, the coefficients change.

The 1985 Radio Yearbook published an antenna with a slightly odd name. It is depicted as an ordinary isosceles triangle with a perimeter of 41.4 m and, obviously, therefore, did not attract attention. As it turned out later, it was in vain. I just needed a simple multi-band antenna, and I hung it at a low height - about 7 meters. The length of the supply cable RK-75 is about 56 m (half-wave repeater).

The measured SWR values ​​practically coincided with those given in the Yearbook. Coil L1 is wound on an insulating frame with a diameter of 45 mm and contains 6 turns of PEV-2 wire with a thickness of 2 ... 2 mm. HF transformer T1 is wound with MGSHV wire on a 400NN 60x30x15 mm ferrite ring, contains two windings of 12 turns each. The size of the ferrite ring is not critical and is selected based on the input power. The power cable is connected only as shown in the figure, if you turn it on the other way around, the antenna will not work. The antenna does not require adjustment, the main thing is to accurately maintain its geometric dimensions. When working on a range of 80 m, in comparison with other simple antennas, it loses to transmit - the length is too small. At the reception, the difference is practically not felt. Measurements carried out by G. Bragin's HF bridge ("R-D" No. 11) showed that we are dealing with a non-resonant antenna.

The frequency response meter only shows the resonance of the power cable. It can be assumed that a fairly universal antenna (from simple ones) has turned out, has small geometric dimensions and its SWR practically does not depend on the suspension height. Then it became possible to increase the suspension height up to 13 meters above the ground. And in this case, the SWR value for all the main amateur bands, except for the 80-meter one, did not exceed 1.4. At the eighties, its value ranged from 3 to 3.5 at the upper frequency of the range, therefore, a simple antenna tuner is additionally used to match it. Later we managed to measure SWR on the WARC bands. There the VSWR value did not exceed 1.3. Antenna drawing is shown in the figure.

GROUND PLANE at 7 MHz

A vertical antenna has several advantages when operating in low frequency bands. However, due to its large size, it is not possible to install it everywhere. Decreasing the antenna height leads to a drop in the radiation resistance and an increase in losses. A wire mesh screen and eight radial wires are used as an artificial "ground". The antenna is powered by a 50-ohm coaxial cable. The VSWR of the antenna tuned with the series capacitor was 1.4. Compared to the previously used “Inverted V” antenna, this antenna provided a loudness gain of 1 to 3 points when used with DX.

QST, 1969, N 1 Radio amateur S. Gardner (K6DY / W0ZWK) applied a capacitive load at the end of the "Ground Plane" antenna at 7 MHz (see figure), which reduced its height to 8 m. The load is a cylinder of wire mesh.

P.S. Apart from QST, the description of this antenna was published in the magazine "Radio". In the year 1980, while still a novice radio amateur, he produced this version of the GP. I made a capacitive load and artificial earth from a galvanized mesh, since there was plenty of it in those days. Indeed, the antenna outperformed Inv.V. on long runs. But then putting on the classic 10-meter GP, I realized that it was not worth bothering with making the container on the top of the pipe, but it would be better to make it two meters longer. The complexity of manufacturing does not pay off the design, not to mention the materials for the manufacture of the antenna.

Antenna DJ4GA

In appearance, it resembles the generatrix of a disc-cone antenna, and its overall dimensions do not exceed the dimensions of a conventional half-wave dipole. Comparison of this antenna with a half-wave dipole having the same suspension height showed that it is somewhat inferior to the dipole for short-range SHORT-SKIP communications, but is much more efficient. it with long-distance communications and with communications carried out with the help of the earth wave. The described antenna has a large bandwidth in comparison with a dipole (by about 20%), which reaches 550 kHz in the range of 40 m (in terms of VSWR up to 2). With a corresponding change in size, the antenna can be used on other bands. The introduction of four notch circuits into the antenna, similar to how it is done in the W3DZZ antenna, allows an efficient multi-band antenna to be realized. The antenna is powered by a coaxial cable with a characteristic impedance of 50 ohms.

P.S. I made this antenna. All dimensions have been consistent, identical to the picture. It was installed on the roof of a five-story building. When crossing from a triangle of the 80-meter range, located horizontally, on short routes, the loss was 2-3 points. It was checked during communications with the stations of the Far East (Equipment for receiving R-250). She won a maximum of one and a half points from the triangle. When compared with the classic GP, I lost one and a half points. The equipment was home-made, UW3DI amplifier 2xGU50.

All-wave amateur antenna

The antenna of the French radio amateur is described in the magazine "CQ". According to the author of this design, the antenna gives a good result when working on all shortwave amateur bands - 10, 15, 20, 40 and 80 m. It does not require any special careful calculation (except for calculating the length of the dipoles) or precise tuning.

It should be installed immediately so that the maximum of the directivity characteristic is oriented in the direction of preferential connections. The feeder of such an antenna can be either two-wire, with a characteristic impedance of 72 ohms, or coaxial, with the same characteristic impedance.

For each band, except for the 40 m band, the antenna has a separate half-wave dipole. On the 40-meter range, a dipole of the 15 m range works well in such an antenna. All dipoles are tuned to the middle frequencies of the corresponding amateur bands and are connected in the center in parallel to two short copper wires. The feeder is soldered to the same wires from below.

Three plates of dielectric material are used to insulate the center wires from each other. Holes are made at the ends of the plates for fastening the wires of the dipoles. All the connection points of the wires in the antenna are soldered, and the connection point of the feeder is wrapped with plastic tape to prevent moisture from entering the cable. The calculation of the length L (m) of each dipole is carried out according to the formula L = 152 / fcp, where fav is the center frequency of the range in MHz. Dipoles are made of copper or bimetallic wire, braces - wire or rope. Antenna height - any, but not less than 8.5 m.

P.S. It was also installed on the roof of a five-story building, the 80-meter dipole was excluded (the size and configuration of the roof did not allow). The masts were made of dry pine, the butt is 10 cm in diameter, and the height is 10 meters. Antenna blades were made from a welding cable. The cable was cut, one core was taken, consisting of seven copper wires. I additionally twisted it a little to increase the density. Proved to be normal, separately suspended dipoles. For work, it is a perfectly acceptable option.

Switchable dipoles with active power supply

The switchable antenna is an active powered two-element linear antenna designed to operate in the 7 MHz range. The gain is about 6 dB, the front-to-back ratio is 18 dB, and the sideways ratio is 22-25 dB. DN width at half power level is about 60 degrees For 20 m range L1 = L2 = 20.57 m: L3 = 8.56 m
Bimetal or ant. rope 1.6 ... 3 mm.
I1 = I2 = 14m 75 Ohm cable
I3 = 5.64m 75 Ohm cable
I4 = 7.08m 50 Ohm cable
I5 = arbitrary length 75 ohm cable
K1.1 - HF relay REV-15

As can be seen from Fig. 1, two active vibrators L1 and L2 are located at a distance L3 (phase shift 72 degrees) from each other. The elements are powered in antiphase, the total phase shift is 252 degrees. K1 provides switching of the direction of radiation by 180 degrees. I3 - phase-shifting loop I4 - quarter-wave matching section. Tuning the antenna consists in adjusting the dimensions of each element in turn to minimize the SWR with the second element short-circuited through a half-wave repeater 1-1 (1.2). SWR in the middle of the range does not exceed 1.2, at the edges of the range -1.4. The dimensions of the vibrators are given for a suspension height of 20 m. From a practical point of view, especially when working in competitions, a system consisting of two similar antennas located perpendicular to each other and spaced apart in space has proven itself well. In this case, a switch is placed on the roof, instantaneous switching of the DN in one of four directions is achieved. One of the options for the location of antennas among typical urban developments is proposed in Fig. 2 This antenna has been used since 1981, has been repeated many times on different QTHs, with its help tens of thousands of QSOs have been made with more than 300 countries of the world.

From the UX2LL website the original source “Radio No. 5, page 25 S. Firsov. UA3LD

Beam antenna for 40 meters with switchable radiation pattern

The antenna schematically shown in the figure is made of copper wire or bimetal with a diameter of 3 ... 5 mm. The matching line is made of the same material. Relays from the RSB radio station are used as switching relays. The matcher uses a variable capacitor from a conventional broadcasting receiver, carefully protected from moisture ingress. The relay control wires are attached to a nylon extension cord running along the centerline of the antenna. The antenna has a wide radiation pattern (about 60 °). The front-to-back ratio of radiation is within 23 ... 25 dB. The calculated gain is 8 dB. The antenna was operated for a long time at the UK5QBE station.

Vladimir Latyshenko (RB5QW) Zaporozhye

P.S. Outside my roof, as an exit option, out of interest I conducted an experiment with an antenna designed as Inv.V. The rest was gleaned and performed as in this design. The relay used automotive, four-pin, metal case. Since I used a 6ST132 battery for power. TS-450S hardware. One hundred watts. Indeed the result, as they say on the face! When switching to the east, they started calling Japanese stations. VK and ZL, in the direction were slightly to the south, made their way with difficulty through the stations of Japan. I will not describe the west, everything thundered! The antenna is cool! Too bad there is not enough space on the roof!

Multi-band dipole on WARC bands

The antenna is made of 2 mm copper wire. I have insulating spacers made of 4 mm thick PCB (it is possible from wooden strips) on which insulators for external wiring are fixed with bolts (MB). The antenna is powered by a coaxial cable of the RK 75 type of any reasonable length. The lower ends of the insulator bars must be stretched with a nylon cord, then the entire antenna stretches well and the dipoles do not overlap with each other. On this antenna, a number of interesting DX-QSOs were made with all continents using the UA1FA transceiver with one GU29 without RA.

DX 2000 antenna

Shortwave often use vertical antennas. To install such antennas, as a rule, a small free space is required, therefore for some radio amateurs, especially those who live in densely populated urban areas), a vertical antenna is the only opportunity to broadcast on short waves. One of the still little-known vertical antennas operating on all HF bands is antenna DX 2000. In favorable conditions the antenna can be used for DX - radio communications, but when working with local correspondents (at distances up to 300 km.) it is inferior to a dipole. As you know, a vertical antenna installed over a well-conductive surface has almost ideal "DX-properties", i. E. very low angle of radiation. This does not require a high mast. Multi-band vertical antennas are typically designed with traps and operate in much the same way as single-band quarter-wave antennas. Broadband vertical antennas used in professional HF radio communication have not found a great response in HF radio amateur, but they have interesting properties.

On the The figure shows the most popular vertical antennas among radio amateurs - a quarter-wave radiator, an electrically extended vertical radiator and a vertical radiator with ladders. An example of the so-called. An exponential antenna is shown on the right. Such a bulk antenna has good efficiency in the frequency band from 3.5 to 10 MHz and quite satisfactory matching (VSWR<3) вплоть до верхней границы КВ диапазона (30 МГц). Очевидно, что КСВ = 2 - 3 для транзисторного передатчика очень нежелателен, но, учитывая широкое распространение в настоящее время антенных тюнеров (часто автоматических и встроенных в трансивер), с высоким КСВ в фидере антенны можно мириться. Для лампового усилителя, имеющего в выходном каскаде П - контур, как правило, КСВ = 2 - 3 не представляет проблемы. Вертикальная антенна DX 2000 является своеобразным гибридом узкополосной четвертьволновой антенны (Ground plane), настроенной в резонанс в некоторых любительских диапазонах, и широкополосной экспоненциальной антенны. Основа антенны-трубчатый излучатель длиной около 6 м. Он собран из алюминиевых труб диаметром 35 и 20 мм., вставленных друг в друга и образующих четвертьволновый излучатель на частоту примерно 7 МГц. Настройку антенны на частоту 3,6 МГц обеспечивает включённая последовательно катушка индуктивности 75 МкГн, к которой подсоединена тонкая алюминиевая tube 1.9 m long. The matching device uses an inductance coil of 10 MkH, to the taps of which the cable is connected. in addition, 4 side emitters made of copper wire in PVC insulation with lengths of 2480, 3500, 5000 and 5390 mm are connected to the coil. For fastening, the emitters are lengthened with nylon cords, the ends of which converge under a 75 MkH coil. When working in the range of 80 m, grounding or counterweights are required, at least for protection against thunderstorms. To do this, several galvanized strips can be buried deep in the ground. When mounting the antenna on the roof of a house, it is very difficult to find any "ground" for HF. Even a well-made earthing on the roof does not have a zero potential with respect to the "earth", therefore it is better to use metal for earthing on a concrete roof.
structures with a large surface area. In the used matching device, grounding is connected to the output of the coil, in which the inductance before the outlet, where the cable braid is connected, is 2.2 MkH. Such a low inductance is insufficient to suppress currents flowing along the outer side of the coaxial cable braid, therefore, a shut-off choke should be made by winding about 5 m of cable into a coil with a diameter of 30 cm.For effective operation of any quarter-wave vertical antenna (including DX 2000) to make a system of quarter-wave counterweights. The DX 2000 antenna was manufactured at the SP3PML radio station (PZK Army Shortwave and Amateur Radio Club).

Antenna design sketch is shown in the figure. The emitter was made of durable duralumin pipes with a diameter of 30 and 20 mm. The braces used to fasten the copper wires-emitters must be resistant to both stretching and weather conditions. The diameter of copper wires should be chosen no more than 3 mm (to limit their own weight), and it is advisable to use wires with insulation, which will ensure resistance to weather conditions. To fix the antenna, use strong insulating ropes that do not stretch when the weather conditions change. Spacers for copper wires of emitters should be made of dielectric (for example, PVC pipes with a diameter of 28 mm), but to increase rigidity, they can be made from a wooden block or other, as lightweight material as possible. The entire antenna structure is mounted on a steel pipe no longer than 1.5 m, previously rigidly attached to the base (roof), for example, with steel guy wires. The antenna cable can be connected via a connector, which must be electrically isolated from the rest of the structure.

For tuning the antenna and matching its impedance with the wave impedance of the coaxial cable, coils with an inductance of 75 MkH (node ​​A) and 10 MkH (node ​​B) are intended. The antenna is tuned to the required sections of the HF bands by selecting the inductance of the coils and the position of the taps. The installation site of the antenna should be free from other structures, best of all, at a distance of 10-12 m, then the influence of these structures on the electrical characteristics of the antenna is small.

Addition to the article:

If the antenna is installed on the roof of an apartment building, its installation height should be more than two meters from the roof to the counterweights (for safety reasons). I strongly do not recommend connecting the antenna ground to the common ground of a residential building or to any fittings that make up the roof structure (in order to avoid huge mutual interference). It is better to use individual grounding, located in the basement of the house. It should be pulled in the communication niches of the building or in a separate pipe pinned to the wall from bottom to top. The use of a lightning arrestor is possible.

V. Bazhenov UA4CGR

Method for accurate calculation of cable length

Many radio amateurs use 1/4 wave and 1/2 wave coaxial lines. They are needed as resistance transformers for impedance repeaters, phase delay lines for antennas with active power supply, etc. The simplest method, but also the most inaccurate, is the method of multiplying part of the wavelength by coefficient 0.66, but it is not always suitable when it is necessary to be accurate enough
calculate the length of the cable, for example 152.2 degrees.

Such accuracy is sometimes necessary for antennas with active power supply, where the quality of the antenna depends on the phasing accuracy.

The coefficient 0.66 is taken as the average, because for the same dielectric, the dielectric constant can deviate noticeably, and therefore the coefficient will also deviate. 0.66. I would like to suggest a method described by ON4UN.

It is simple, but requires instrumentation (a transceiver or oscillator with a digital scale, a good SWR meter and a 50 or 75 ohm dummy load depending on the Z. of the cable) Fig. 1. The figure shows how this method works.

The cable from which it is planned to make the desired section must be short-circuited at the end.

Next, let's turn to a simple formula. Let's say we need a 73 degree cut to operate at 7.05 MHz. Then our section of cable will be exactly 90 degrees at a frequency of 7.05 x (90/73) = 8.691 MHz. This means that when tuning the transceiver in frequency, at 8.691 MHz, our SWR meter should indicate the minimum SWR, since at this frequency, the cable length will be 90 degrees, and for a frequency of 7.05 MHz it will be exactly 73 degrees. When shorted, it will invert the short circuit into infinite resistance and thus will not affect the SWR meter readings at 8.691 MHz. For these measurements, either a sufficiently sensitive SWR meter is required, or a sufficiently powerful equivalent load, since you will have to increase the power of the transceiver for reliable operation of the SWR meter, if it does not have enough power for normal operation. This method gives very high measurement accuracy, which is limited by the accuracy of the SWR meter and the accuracy of the transceiver scale. For measurements, you can also use the VA1 antenna analyzer, which I already mentioned earlier. An open cable will indicate zero impedance at the calculated frequency. It is very convenient and fast. I think this method will be very useful for radio amateurs.

Alexander Barsky (VAZTTT), vаЗ [email protected] com

Asymmetric GP antenna

The antenna is (Fig. 1) nothing more than a "groundplane" with an elongated vertical radiator 6.7 m high and four counterweights 3.4 m long each. A broadband resistance transformer (4: 1) is installed at the feed point.

At first glance, the indicated antenna dimensions may appear to be incorrect. However, adding the length of the radiator (6.7 m) and the counterweight (3.4 m), we make sure that the total antenna length is 10.1 m.Considering the shortening factor, this is Lambda / 2 for the 14 MHz band and 1 Lambda for 28 MHz.

The resistance transformer (Fig. 2) is made according to the generally accepted technique on a ferrite ring from the OS of a black and white TV and contains 2 × 7 turns. It is installed at the point where the antenna input impedance is about 300 ohms (a similar excitation principle is used in modern versions of the Windom antenna).

The average vertical diameter is 35 mm. To achieve resonance at the required frequency and more accurate matching with the feeder, you can change the size and position of the counterweights within a small range. In the author's version, the antenna has a resonance at frequencies of about 14.1 and 28.4 MHz (SWR = 1.1 and 1.3, respectively). If desired, by increasing the dimensions indicated in Fig. 1 by about two times, it is possible to achieve the operation of the antenna in the 7 MHz range. Unfortunately, in this case, the radiation angle in the 28 MHz range will "deteriorate". However, using a U-shaped matching device installed near the transceiver, you can use the author's version of the antenna for operation in the 7 MHz range (albeit with a loss of 1.5 ... 2 points in relation to the half-wave dipole), as well as in the 18, 21 bands , 24 and 27 MHz. For five years of operation, the antenna has shown good results, especially in the 10-meter range.

Shortwave people often have difficulty installing full-size antennas for low-frequency HF bands. One of the possible versions of the shortened (approximately two times) dipole of the 160 m range is shown in the figure. The total length of each half of the radiator is about 60 m.

They are folded in three, as schematically shown in figure (a) and are held in this position by two end (c) and several intermediate (b) insulators. These insulators, as well as a similar central insulator, are made of a non-hygroscopic dielectric material with a thickness of about 5 mm. The distance between adjacent conductors of the antenna web is 250 mm.

A coaxial cable with a characteristic impedance of 50 ohms is used as a feeder. The antenna is tuned to the middle frequency of the amateur band (or its required section - for example, telegraph) by moving two jumpers connecting its extreme conductors (in the figure they are shown by dashed lines), and observing the symmetry of the dipole. The jumpers must not have electrical contact with the center conductor of the antenna. With the dimensions indicated in the figure, the resonant frequency of 1835 kHz was achieved by installing jumpers at a distance of 1.8 m from the ends of the canvas. The standing wave ratio at the resonant frequency is 1.1. There are no data on its dependence on frequency (i.e., on the antenna bandwidth) in the article.

Antenna 28 and 144 MHz

Rotating directional antennas are required to operate reasonably efficiently in the 28 and 144 MHz bands. However, it is usually not possible to use two separate antennas of this type in a radio station. Therefore, the author made an attempt to combine antennas of both bands, making them in the form of a single design.

The dual-band antenna is a double “square” at 28 MHz, on the carrier traverse of which a nine-element wave channel at 144 MHz is fixed (Fig. 1 and 2). As practice has shown, their mutual influence on each other is insignificant. The influence of the wave channel is compensated by a slight decrease in the perimeters of the "square" frames. “Square”, in my opinion, improves the parameters of the wave channel, increasing the gain and suppression of backward radiation. The antennas are powered by means of 75-ohm coaxial cable feeders. The “square” feeder is included in the gap in the lower corner of the vibrator frame (left in Fig. 1). A slight asymmetry with this inclusion causes only a slight skew of the directional pattern in the horizontal plane and does not affect the rest of the parameters.

The wave channel feeder is switched on through the balun U-bend (Fig. 3). As shown by measurements of the VSWR in the feeders of both antennas does not exceed 1.1. The antenna mast can be made of steel or duralumin pipes with a diameter of 35-50 mm. A gearbox is attached to the mast, combined with a reversible motor. A “square” traverse made of pine wood is screwed to the gearbox flange by means of two metal plates with M5 bolts. Traverse section - 40X40 mm. At its ends, crosses are fixed, which are supported by eight wooden poles "square" with a diameter of 15-20 mm. The frames are made of bare copper wire with a diameter of 2 mm (you can use a wire PEV-2 1.5 - 2 mm). The perimeter of the reflector frame is 1120 cm, the vibrator is 1056 cm. The wave channel can be made of copper or brass tubes or rods. Its traverse is fixed on the "square" traverse with two brackets. Antenna settings have no special features.

If you repeat the recommended sizes exactly, it may not be needed. The antennas on the RA3XAQ have shown good results over the years. A lot of DX connections were made at 144 MHz - with Bryansk, Moscow, Ryazan, Smolensk, Lipetsk, Vladimir. More than 3.5 thousand QSOs were established at 28 MHz, among them - with VP8, CX, LU, VK, KW6, ZD9, etc. The design of the dual-band antenna was repeated three times by Kaluga radio amateurs (RA3XAC, RA3XAS, RA3XCA) and also received positive ratings ...

P.S. In the eighties of the last century, there was exactly such an antenna. Basically I did it for work via low-orbit satellites ... RS-10, RS-13, RS-15. I used UW3DI with Zhutyaevsky transverter, and received R-250. Everything worked out well with ten watts. The squares on the top ten worked well, a lot of VK, ZL, JA, etc. ... And the passage was wonderful then!

Long version W3DZZ

The antenna shown in the figure is an elongated version of the well-known W3DZZ antenna, adapted to work on the 160, 80, 40 and 10 m bands. To hang its web, a "span" of about 67 m is required.

The power cable can have a characteristic impedance of 50 or 75 ohms. The coils are wound on nylon frames (water pipes) with a diameter of 25 mm with a PEV-2 wire 1.0 turn to turn (38 in total). Capacitors C1 and C2 are composed of four series-connected capacitors KSO-G with a capacity of 470 pF (5%) for an operating voltage of 500V. Each capacitor string is housed inside a coil and sealed with sealant.

For fastening the capacitors, you can also use a fiberglass plate with foil "spots", to which the leads are soldered. The circuits are connected to the antenna web as shown in the figure. When using the above elements, there were no failures during the operation of the antenna together with a radio station of the first category. The antenna, suspended between two nine-storey buildings and fed through a cable RK-75-4-11 about 45 m long, provided a VSWR of no more than 1.5 at frequencies of 1840 and 3580 kHz and no more than 2 in the range of 7 ... 7.1 and 28, 2 ... 28.7 MHz. The resonant frequency of the notch filters L1C1 and L2C2, measured by the GIR before connecting to the antenna, was 3580 kHz.

W3DZZ with coaxial cable ladders

This design is based on the ideology of the W3DZZ antenna, but the 7 MHz barrage loop (ladder) is made of a coaxial cable. The antenna drawing is shown in Fig. 1, and the design of the coaxial ladder is shown in Fig. 2. The vertical ends of the 40-meter strip of the dipole have a size of 5 ... 10 cm and are used to tune the antenna to the desired section of the range. The ladders are made of a 50 or 75-ohm cable 1.8 m long, laid in a twisted coil with a diameter of 10 cm as shown in fig. 2. The antenna is powered by a coaxial cable through a balun consisting of six ferrite rings, put on the cable near the power points.

P.S. During the manufacture of the antenna, no tuning was required as such. I paid special attention to sealing the ends of the ladders. First, I filled the ends with electrical wax, you can use paraffin from an ordinary candle, then covered it with silicone sealant. Which is sold in car dealerships. Best quality sealant is gray.

Antenna "Fuchs" for a range of 40 m

Luc Pistorius (F6BQU)
Translation by Nikolay Bolshakov (RA3TOX), E-mail: boni (doggie) atnn.ru

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The version of the matching device shown in Fig. 1 differs in that the precise adjustment of the antenna web length is carried out from the “nearby” end (next to the matching device). This is really very convenient, since it is impossible to set the exact length of the antenna strip in advance. The environment will do its job and, as a result, will inevitably change the resonant frequency of the antenna system. In this design, the antenna is tuned to resonance with a piece of wire about 1 meter long. This piece is next to you and is convenient for tuning the antenna into resonance. In the author's version, the antenna is installed in the garden. One end of the wire goes into the attic, the other is fixed on a pole 8 meters high, installed in the back of the garden. The length of the antenna wire is 19 m. In the attic, the end of the antenna is connected by a 2-meter piece to a matching device. Total - the total length of the antenna strip -21 m. The counterweight 1 m long is located together with the control system in the attic of the house. Thus, the entire structure is under a roof and therefore protected from atmospheric elements.

For the 7 MHz band, the elements of the device have the following ratings:
Cv1 = Cv2 = 150 pf;
L1 - 18 turns of copper wire with a diameter of 1.5 mm on a frame with a diameter of 30 mm (PVC pipe);
L1 - 25 turns of copper wire with a diameter of 1 mm on a frame with a diameter of 40 mm (PVC pipe); We adjust the antenna to a minimum SWR. First, we set the minimum SWR with the capacitor Cv1, then we try to reduce the SWR with the capacitor Cv2 and finally make the adjustment, choosing the length of the compensating segment (counterweight). Initially, we choose the length of the antenna wire a little more than a half-wave and then compensate for it with a counterweight. The Fuchs antenna is a familiar stranger. An article with this title told about this antenna and two variants of matching devices for it, proposed by the French radio amateur Luc Pistorius (F6BQU).

Field trip antenna VP2E

Antenna VP2E (Vertically Polarized 2-Element) is a combination of two half-wave radiators, due to which it has a two-way symmetrical radiation pattern with unsharp minima. The antenna has a vertical (see name) polarization of radiation and a directional pattern pressed to the ground in the vertical plane. The antenna provides a gain of +3 dB in comparison with an omnidirectional radiator in the direction of emission maxima and suppression of the order of -14 dB in the AP notches.

The single-band version of the antenna is shown in Fig. 1, its dimensions are summarized in the table.
Element Length in L Length for the 80th range I1 = I2 0.492 39 m I3 0.139 11 m h1 0.18 15 m h2 0.03 2.3 m The radiation pattern is shown in Fig. 2. For comparison, the directional diagrams of a vertical emitter and a half-wave dipole are superimposed on it. Figure 3 shows a five-band version of the VP2E antenna. Its resistance at the feed point is about 360 ohms. When the antenna was powered via a 75 Ohm cable through a 4: 1 matching transformer on a ferrite core, the VSWR was 1.2 at a range of 80 m; 40 m - 1.1; 20 m - 1.0; 15 m - 2.5; 10 m - 1.5. It is likely that a better match can be achieved with a two-wire power supply through an antenna tuner.

"Secret" antenna

In this case, the vertical "legs" are 1/4 long, and the horizontal part is 1/2. Two vertical quarter-wave emitters are obtained, powered in antiphase.

An important advantage of this antenna is that the radiation resistance is about 50 ohms.

It is powered at the bend point, and the central cable core is connected to the horizontal part, and the braid to the vertical one. Before making an antenna for the 80m range, I decided to mock-up at a frequency of 24.9 MHz, because I had an oblique dipole for this frequency and, therefore, I had something to compare with. At first I listened to the NCDXF beacons and did not notice the difference: somewhere better, somewhere worse. When UA9OC, located 5 km away, gave a weak tuning signal, all doubts disappeared: in the direction perpendicular to the canvas, the U-shaped antenna has an advantage of at least 4 dB with respect to the dipole. Then there was an antenna for 40 m and, finally, for 80 m. Despite the simplicity of the design (see Fig. 1), it was not easy to hook it to the tops of poplars in the yard.

I had to make a halberd with a bowstring made of steel millimeter wire and an arrow from a 6 mm duralumin tube 70 cm long with a weight in the bow and with a rubber tip (just in case!). At the rear end of the arrow, I fixed a 0.3 mm fishing line with a cork, with it I launched the arrow to the top of the tree. Using a thin fishing line, I tightened another, 1.2 mm, with which I hung the antenna from a 1.5 mm wire.

One end turned out to be too low, it would certainly have been pulled by the kids (the yard is common!), So I had to bend it and let my tail go horizontally at a height of 3 m from the ground. For power, I used a 50-ohm cable of 3 mm in diameter (by insulation) for ease and as less noticeable. Tuning consists in adjusting the length, because the surrounding objects and the ground somewhat lower the calculated frequency. It should be remembered that we shorten the end closest to the feeder by D L = (D F / 300,000) / 4 m, and the far end - three times as much.

It is assumed that the diagram in the vertical plane is flattened at the top, which manifests itself in the effect of "leveling" the signal strength from far and near stations. In the horizontal plane, the diagram is elongated in the direction perpendicular to the antenna surface. It is difficult to find trees with a height of 21 meters (for 80 m range), so you have to bend the lower ends and let them horizontally, while the antenna resistance decreases. Apparently, such an antenna is inferior to a full-size GP, since the radiation pattern is not circular, but it does not need counterweights! I am quite satisfied with the results. At least this antenna seemed to me much better than the previous Inverted-V. Well, for the "Field Day" and for the not very "cool" DX-pedition in the low-frequency ranges, it is probably not equal to it.

From the UX2LL website

Compact 80 meter loop antenna

Many radio amateurs have country cottages and often the small size of the area on which the house is located does not allow having a sufficiently effective HF antenna.

For DX, it is preferable that the antenna radiates at small angles to the horizon. Moreover, its designs must be easily repeatable.

The proposed antenna (Fig. 1) has a radiation pattern similar to that of a vertical quarter-wave radiator. Its maximum radiation in the vertical plane falls at an angle of 25 degrees to the horizon. Also, one of the advantages of this antenna is the simplicity of the design, since it is enough to use a twelve-meter metal mast for its installation. Power is supplied to the middle of any of the vertically located lateral sides. If the indicated dimensions are observed, its input impedance is in the range of 40 ... 55 Ohm.

Practical tests of the antenna have shown that it gives a gain in signal level for remote correspondents on paths of 3000… .6000 km in comparison with such antennas as “half-wave Inverted Vee? horizontal Delta-Loor ”and quarter-wave GP with two radials. The difference in the signal level when compared with the "half-wave dipole" antenna on paths over 3000 km reaches 1 point (6 dB). The measured SWR was 1.3-1.5 in the range.

RV0APS Dmitry SHABANOV Krasnoyarsk

Receiving antenna 1.8 - 30 MHz

Many going out into nature take various radios with them. There are enough of them in stock now. Various brands of Grundig satellit, Degen, Tecsun ... As a rule, a piece of wire is used for the antenna, which, in principle, is quite enough. The antenna shown in the figure is a kind of ABC antenna, and has a directional pattern. When received on a radio Degen DE1103, it showed its selective qualities, the signal to the correspondent when it was directed increased by 1-2 points.

Shortened dipole by 160 meters

An ordinary dipole is perhaps one of the simplest but effective antennas. However, for a range of 160 meters, the length of the emitting part of the dipole exceeds 80 m, which usually causes difficulties in its installation. One of the possible ways to overcome them is to introduce shortening coils into the emitter. Shortening the antenna usually leads to a decrease in its efficiency, but sometimes the radio amateur is forced to make a similar compromise. A possible embodiment of a dipole with extension coils for a range of 160 meters is shown in Fig. 8. The overall dimensions of the antenna do not exceed the dimensions of a conventional dipole for a range of 80 meters. Moreover, such an antenna can be easily converted into a dual-band antenna by adding relays that would close both coils. In this case, the antenna turns into an ordinary dipole for a range of 80 meters. If there is no need to work on two bands, and the place for installing the antenna makes it possible to use a dipole with a length greater than 42 m, then it is advisable to use an antenna with the maximum possible length.

The inductance of the extension coil in this case is calculated by the formula: Here L is the inductance of the coil, μHp; l is the length of half of the radiating part, m; d - antenna wire diameter, m; f - operating frequency, MHz. According to the same formula, the inductance of the coil is calculated even if the place for installing the antenna is less than 42 m. and this, in particular, further impairs its effectiveness.

DL1BU antenna modification

During the year my second category radio station has been using a simple antenna (see Fig. 1), which is a modification of the DL1BU antenna. It works in the ranges of 40, 20 and 10 m, does not require the use of a symmetrical feeder, is well matched, and is easy to manufacture. A transformer on a ferrite ring is used as a matching and balancing element. grade VCh-50 with a cross section of 2.0 sq. cm. The number of turns of its primary winding is 15, the secondary is 30, the wire is PEV-2. with a diameter of 1 mm. When using a ring of a different section, it is necessary to re-select the number of turns using the diagram shown in Fig. 2. As a result of the selection, it is necessary to obtain a minimum SWR in the range of 10 meters. The antenna made by the author has a SWR of 1.1 at 40 m, 1.3 at 20 m and 1.8 at 10 m.

V. KONONOV (UY5VI) Donetsk

P.S. In the manufacture of the structure, I used a U-shaped core from a line transformer of a TV, without changing the turns, I received a similar SWR value, with the exception of the 10 meter range. The best VSWR was 2.0, and naturally changed as the frequency changed.

Shortened antenna 160 meters

The antenna is an asymmetrical dipole, which is fed through a matching transformer with a coaxial cable with a characteristic impedance of 75 Ohm. The antenna is best made of bimetal with a diameter of 2 ... 3 mm - the antenna cable and copper wire stretch over time, and the antenna is detuned.

Matching transformer T can be made on an annular magnetic circuit with a cross section of 0.5 ... 1 cm2 of ferrite with an initial magnetic permeability of 100 ... 600 (better - grade NN). It is possible, in principle, to use magnetic cores from fuel assemblies of old TVs, which are made of HH600 material. The transformer (it must have a transformation ratio of 1: 4) is wound in two wires, and the terminals of the windings A and B (the indices "n" and "k" denote the beginning and end of the winding, respectively) are connected, as shown in Fig. 1b.

For the transformer windings, it is best to use a stranded installation wire, but ordinary PEV-2 can also be used. Winding is carried out with two wires at once, laying them tightly, turn to turn, along the inner surface of the magnetic circuit. Overlapping of wires is not allowed. On the outer surface of the ring, the turns are placed with a uniform pitch. The exact number of double turns is insignificant - it can be in the range of 8 ... 15. The manufactured transformer is placed in a plastic cup of the appropriate size (Fig. 1c pos. 1) and filled with epoxy resin. A screw 5 5 ... 6 mm long is sunk into the non-solidified resin in the center of the transformer 2 with the head down. It is used to fasten the transformer and the coaxial cable (using the clip 4) to the textolite plate 3. This plate 80 mm long, 50 mm wide and 5 ... 8 mm thick forms the central antenna insulator - the antenna canvases are also attached to it. The antenna is tuned to a frequency of 3550 kHz by selecting the length of each antenna web to the minimum SWR (in Fig. 1 they are indicated with a certain margin). It is necessary to shorten the shoulders gradually by about 10 ... 15 cm at a time. After completing the adjustment, all connections are carefully soldered, and then embedded in paraffin. Be sure to cover the exposed portion of the coaxial cable with paraffin wax. Practice has shown that paraffin protects antenna parts from moisture better than other sealants. The paraffin coating does not age in the air. The antenna made by the author had a bandwidth at SWR = 1.5 on the 160 m - 25 kHz range, about 50 kHz on the 80 m range, about 100 kHz on the 40 m range, and about 200 kHz on the 20 m range. On the 15 m range, the VSWR was in the range of 2… 3.5, and on the 10 m range, it was in the range of 1.5… 2.8.

Laboratory of the CRK DOSAAF. 1974 year

Car HF antenna DL1FDN

In the summer of 2002, despite poor communication conditions on the 80m band, I made a QSO with Dietmar, DL1FDN / m, and was pleasantly surprised by the fact that my correspondent was working from a moving car Intrigued, I inquired about the output power of his transmitter and the antenna design ... Dietmar. DL1FDN / m, willingly shared information about his homemade car antenna and kindly allowed me to tell about it. The information in this note was recorded during our QSO. Obviously his antenna really works! Dietmar uses an antenna system, the design of which is shown in the figure. The system includes a radiator, an extension coil and a matching device (antenna tuner). The radiator is made of a copper-plated steel pipe 2 m long installed on an insulator. The extension coil L1 is wound coil to coil. Its coil data for the 160 and 80 m bands are shown in the table ... For operation in the 40 m range, the L1 coil contains 18 turns wound with a 02 mm wire on a 0100 mm frame. In the ranges of 20, 17, 15, 12 and 10 m, part of the turns of the coil of the 40 m range is used. The taps on these ranges are selected experimentally. The matching device is an LC circuit consisting of a variable inductance coil L2, which has a maximum inductance of 27 μH (it is advisable not to use a ball variometer). A variable capacitor C1 must have a maximum capacity of 1500 ... 2000 pF. With a transmitter power of 200 W (this is the power used by DL1FDN / m), the gap between the plates of this capacitor must be at least 1 mm. Capacitors C2, SZ - K15U, but at the specified power you can use KSO-14 or similar.

S1 - ceramic board switch. The antenna is tuned at a specific frequency according to the minimum readings of the SWR meter. The cable connecting the matching device to the SWR meter and the transceiver has a characteristic impedance of 50 ohms, and the SWR meter is calibrated to a 50 ohm antenna equivalent.

If the output impedance of the transmitter is 75 ohms, a 75 ohm coaxial cable should be used, and the VSWR meter should be “balanced” on the equivalent of a 75 ohm antenna. Using the antenna system described and operating from a moving vehicle, the DL1FDN made many interesting radio communications on the 80m band, including QSOs with other continents.

I. Podgorny (EW1MM)

Compact HF antenna

Small-sized loop antennas (the perimeter of the loop is much less than the wavelength) are used in the HF bands mainly only as receiving ones. Meanwhile, with an appropriate design, they can be successfully used on amateur radio stations and as transmitting ones. Such an antenna has a number of important advantages: First, its Q-factor is at least 200, which makes it possible to significantly reduce interference from stations operating on neighboring frequencies. The small bandwidth of the antenna naturally necessitates its adjustment even within the same amateur band. Secondly, a small-sized antenna can operate in a wide frequency range (frequency overlap reaches 10!). And finally, it has two deep minima at small angles of radiation (directional pattern - "eight"). This allows the rotation of the frame (which is easy to do with its small dimensions) to effectively suppress the interference coming from specific directions. The antenna is a frame (one turn), which is tuned to the operating frequency by a variable capacitor - KPI. The shape of the coil is not critical and can be any, but for design reasons, as a rule, they use frames in the form of a square. Antenna operating frequency range depends on the size of the frame. The minimum operating wavelength is approximately 4L (L - frame perimeter). Overlapping in frequency is determined by the ratio of the maximum and minimum values ​​of the KPI capacitance. When using conventional capacitors, the frequency overlap of the loop antenna is about 4, with vacuum capacitors - up to 10. With a transmitter output power of 100 W, the currents in the loop reach tens of amperes, therefore, to obtain acceptable values ​​of the efficiency, the antenna must be made of copper or brass pipes a sufficiently large diameter (approx. 25 mm). Screwed connections must provide reliable electrical contact, excluding the possibility of deterioration due to the appearance of a film of oxides or rust. It is best to solder all connections. A variant of a compact loop antenna designed for use in the amateur bands of 3.5-14 MHz.

A schematic drawing of the entire antenna is shown in Figure 1. In fig. 2 shows the construction of a communication loop with an antenna. The frame itself is made of four copper pipes 1000 in length and 25 mm in diameter. The KPE is included in the lower corner of the frame - it is placed in a box that excludes the effects of atmospheric moisture and precipitation. With a transmitter output power of 100 W, this KPI must be designed for an operating voltage of 3 kV. The antenna is fed with a coaxial cable with a characteristic impedance of 50 Ohm, at the end of which a communication loop is made. The upper section of the hinge according to Figure 2, with the braid removed to a length of about 25 mm, must be protected from moisture, i.e. any compound. The loop is securely attached to the frame at its top corner. The antenna is installed on a mast with a height of about 2000 mm made of insulating material. An antenna made by the author had an operating frequency range of 3.4 ... 15.2 MHz. The standing wave ratio was 2 in the 3.5 MHz bands and 1.5 in the 7 and 14 MHz bands. Comparing it with full-size dipoles, installed at the same height, showed that in the 14 MHz range both antennas are equivalent, at 7 MHz the signal level of the loop antenna is 3 dB less, and at 3.5 MHz - by 9 dB. These results were obtained for large radiation angles. For such radiation angles, when communicating at a distance of up to 1600 km, the antenna had an almost circular radiation pattern, but effectively suppressed local interference with its appropriate orientation, which is especially important for those radio amateurs where the level of interference is high. Antenna bandwidth is typically 20 kHz.

Yu Pogreban, (UA9XEX)

Yagi Antenna 2 Elements x 3 Bands

It is an excellent antenna for field use and for work from home. SWR on all three bands (14, 21, 28) is from 1.00 to 1.5. The main advantage of the antenna is ease of installation - just a few minutes. We put any mast ~ 12 meters high. At the top, a block is fixed through which a nylon cable is passed. The cable is tied to the antenna and it can instantly be raised or lowered. This is important in field conditions, as the weather can change a lot. Removing the antenna is a matter of a few seconds.

Further - only one mast is needed to install the antenna. In the horizontal position, the antenna radiates at large angles to the horizon. If the antenna plane is placed at an angle to the horizon, then the main radiation begins to press against the ground and the more, the more vertically the antenna is suspended. That is, one end is at the top of the mast, and the other is attached to a peg on the ground. (See photo). The closer the peg is to the mast, the more vertical it will be and the closer to the horizon the angle of vertical radiation will be pressed. Like all antennas, it radiates away from the reflector. If the antenna is carried around the mast, then the direction of its radiation can be changed. Since the antenna is attached, as can be seen from the figure, at two points, then, by turning it 180 degrees, you can very quickly change the direction of its radiation to the opposite.

When manufacturing, it is necessary to maintain the dimensions as shown in the figure. We first made it with one reflector - at 14 MHz and it was in the high-frequency part of the 20 meter range.

After the addition of reflectors at 21 and 28 MHz, it began to resonate in the high-frequency part of the telegraph sections, which made it possible to conduct communications in the CW and SSB sections. The resonance curves are gentle and the SWR at the edges is not more than 1.5. We call this antenna Hammock. By the way, in the original antenna, Markus, like the hammocks, had two wooden bars 50x50 mm, between which the elements were stretched. We use fiberglass rods, which made the antenna much lighter. Antenna elements are made of 4 mm diameter antenna cable. Plexiglass spacers between vibrators. If you have any questions, please write: [email protected]

Antenna "Square" with one element at 14 MHz

In one of his books in the late 1980s, W6SAI, Bill Orr proposed a simple antenna - 1 element square, which was installed vertically on a single mast. The antenna was made according to W6SAI with the addition of an RF choke. The square is made for a range of 20 meters (Fig. 1) and is installed vertically on one mast. In continuation of the last knee of a 10-meter army telescope, a piece of fiberglass is inserted about fifty centimeters, in the form of nothing different from the upper knee of the telescope, with a hole at the top, which is the upper insulator. It turned out a square with an angle at the top, an angle at the bottom and two corners on the stretch marks on the sides.

In terms of efficiency, this is the most advantageous option for locating the antenna, which is low above the ground. The feeding point was about 2 meters from the underlying surface. The cable connection unit is a piece of thick fiberglass 100x100 mm, which is attached to the mast and serves as an insulator.

The perimeter of the square is equal to 1 wavelength and is calculated by the formula: Lm = 306.3F MHz. For a frequency of 14.178 MHz. (Lm = 306.3,178) the perimeter will be 21.6 m, i.e. side of the square = 5.4 m. Power supply from the bottom corner with a 75 ohm cable 3.49 meters long, i.e. 0.25 wavelength. This piece of cable is a quarter-wave transformer, transforming Rin. antennas of the order of 120 ohms, depending on the objects surrounding the antenna, with a resistance close to 50 ohms. (46.87 ohms). Most of the 75 ohm length of cable is positioned vertically along the mast. Further, through the RF connector, the main transmission line is a 50 Ohm cable with a length equal to an integer number of half-waves. In my case, this is a 27.93 m section, which is a half-wave repeater. This method of powering is well suited for 50 ohm technology, which today corresponds to R out in most cases. Silos of transceivers and the nominal output impedance of power amplifiers (transceivers) with a P-loop at the output.

When calculating the length of the cable, keep in mind a shortening factor of 0.66-0.68, depending on the type of plastic cable insulation. With the same 50 ohm cable, an RF choke is wound next to the said RF connector. Its data: 8-10 turns on a 150mm mandrel. Winding coil to coil. For antennas for low frequency ranges - 10 turns on a mandrel 250 mm. The RF choke eliminates the curvature of the antenna radiation pattern and acts as a Shut-off Choke for HF currents moving along the cable sheath towards the transmitter. The antenna bandwidth is about 350-400 kHz. with VSWR close to unity. Outside the bandwidth, the VSWR rises dramatically. Antenna polarization is horizontal. The braces are made of wire with a diameter of 1.8 mm. broken by insulators at least every 1-2 meters.

If we change the feed point of the square by feeding it from the side, the result is vertical polarization, which is more preferred for DX. Use the same cable as for horizontal polarization, i.e. a quarter-wave piece of 75 Ohm cable goes to the frame (the central core of the cable is connected to the upper half of the square, and the braid to the bottom), and then the 50 Ohm cable is a multiple of the half-wave. The resonant frequency of the frame will go up by about 200 kHz when the power point is changed. (at 14.4 MHz.), so the frame will have to be lengthened somewhat. An extension wire, a cable of about 0.6-0.8 meters, can be connected to the lower corner of the frame (to the former power point of the antenna). To do this, you need to use a two-wire line segment of the order of 30-40 cm.

Antenna with a capacitive load of 160 meters

According to the reviews of the operators whom I met on the air, they mainly use an 18-meter structure. Of course there are 160-meter enthusiasts who have pins and larger sizes, but this is acceptable, probably, somewhere in the countryside. I personally met a radio amateur from Ukraine, who used this construction with a height of 21.5 meters. When comparing to transmit, the difference between this antenna and the dipole was 2 points, in favor of the pin! According to him, for longer distances the antenna behaves remarkably, to the extent that the correspondent is not heard on the dipole, and the pin draws out the long-range QSO! He used an irrigation, duralumin, thin-walled pipe with a diameter of 160 millimeters. At the joints, he was tightened with a bandage from the same pipes. It was fastened with rivets (riveting gun). According to him, during the ascent, the structure withstood without question. It is not worth concreting, just covered with earth. In addition to the capacitive loads, also used as braces, there are two other sets of braces. Unfortunately, I forgot the call sign of this radio amateur, and I cannot correctly refer to him!

Receiving antenna T2FD for Degen 1103

This weekend I built a T2FD receiving antenna. And ... I was very pleased with the results ... The central polypropylene pipe is gray, 50 mm in diameter. Used in plumbing for draining. Inside there is a transformer on "binoculars" (using EW2CC technology) and a load resistance of 630 Ohm (400 to 600 Ohm is suitable). Antenna sheet from a symmetrical pair of "voles" P-274M.

Attached to the center piece with bolts protruding from the inside. The inside of the pipe is filled with foam. The spacer pipes - 15 mm white, are used for cold water (NO METAL INSIDE !!!).

Installation of the antenna, with all the materials available, took about 4 hours. And most of the time he "killed" by untangling the wires. We "collect" binoculars from such ferrite glasses: Now about where to get them. Such cups are used on USB and VGA monitor cords. Personally, I got them when disassembling decommissioned monics. Which in the cases (open in two halves) I would use as a last resort ... Solid ones are better ... Now about the winding. Wound with a wire similar to PELSHO - stranded, the lower insulation is made of polymaterial, and the upper one is made of fabric. The total wire diameter is about 1.2 mm.

So, through the binoculars it is dangling: PRIMARY - 3 turns, ends on one side; SECONDARY - 3 turns ends on the other side. After winding, we track where the middle of the secondary is - it will be on the other side of its ends. We carefully clean the middle of the secondary housing and connect it to one wire of the primary - this will be a COLD OUTPUT. Well, then everything goes according to the scheme ... In the evening, I threw the antenna to the Degen 1103 receiver. Everything rattles! True, I didn’t hear anyone on 160 (7 pm is still too early), 80 is in full swing, on the troika from Ukraine the guys are good at AM. In general, the buzz is working !!!

From publication: EW6MI

Delta Loop by RZ9CJ

Over the years, most of the existing antennas have been tested on the air. When, after all of them, I did and tried to work on the vertical Delta, I realized how much time and effort I spent on all those antennas - in vain. The only omnidirectional antenna that has brought a ton of enjoyable transceiver hours is the vertically polarized Delta. So I liked it that I made 4 pieces for 10, 15, 20 and 40 meters. The plans are to make it also at 80 m. By the way, almost all of these antennas immediately after construction * hit * more or less by SWR.

All masts are 8 meters high. Pipes 4 meters - from the nearest housing office Above the pipes - bamboo sticks, two bundles up. Oh, and they break, infections. 5 times already changed. It is better to tie them in 3 pieces - it will turn out thicker, but it will also last longer. Poles are inexpensive - in general, the budget option for the best omnidirectional antenna. Compared to a dipole - earth and sky. Really * punched * pile-ups, which was not possible on the dipole. A 50 ohm cable is connected at the feed point to the antenna web. The horizontal wire must be at a height of at least 0.05 waves (thanks to VE3KF), that is, for the 40 meter range, this is 2 meters.

P.S. Horizontal wire, you need to assume the place where the cable is connected to the canvas. I changed the pictures a little, the optimum for the site!

HF portable antenna for 80-40-20-15-10-6 meters

On the website of the Czech radio amateur OK2FJ František Javurek found an antenna design interesting in my opinion, which works on the ranges of 80-40-20-15-10-6 meters. This antenna is an analogue of the MFJ-1899T antenna, although the original costs 80 ye, and a homemade one fits in a hundred rubles. I decided to repeat it. This required a piece of fiberglass tube (from a Chinese fishing rod) 450 mm in size, and diameters from 16 mm to 18 mm at the ends, 0.8 mm lacquered copper wire (disassembled the old transformer) and a telescopic antenna about 1300 mm long (I found only a meter Chinese one from TV, but expanded it with a suitable tube). The wire is wound on a fiberglass tube according to the drawing and taps are made to switch the coils to the desired range. As a switch, I used a wire with crocodiles at the ends. Here's what happened: The range switching and the telescope length are shown in the table. You should not expect any wonderful characteristics from such an antenna, this is just a travel option that will find a place in your bag.

Today I tried it at the reception, on the street just sticking it into the grass (at home she did not work at all), very loudly received 3,4 areas at 40 meters, 6 was barely audible. There was no time today to test it longer, as I try to unsubscribe for the transfer. P.S. More detailed pictures of the antenna device can be found here: link. Unfortunately, there has not yet been an unsubscribe to work on transmission with this antenna. I am extremely interested in this antenna, I will probably have to make and try it in work. In conclusion, I post a photo of the antenna made by the author.

From the site of Volgograd radio amateurs

80m antenna

For more than a year, when working on the 80-meter radio amateur band, I have been using the antenna, the design of which is shown in the figure. The antenna has proven itself well for long-distance communications (for example, with New Zealand, Japan, the Far East, etc.). A 17 meter high wooden mast rests on an insulating plate, which is anchored to the top of a 3 meter high metal pipe. The antenna mount is formed by the working frame braces, a special tier of guy lines (their top point can be at a height of 12-15 meters from the roof) and, finally, a system of counterweights, which are attached to the insulating plate. The working frame (it is made of an antenna cable) is connected at one end to the counterweight system, and at the other end to the central core of the coaxial cable feeding the antenna. It has a characteristic impedance of 75 ohms. The braid of the coaxial cable is also attached to the counterweight system. There are 16 of them in total, each 22 meters long. The antenna is tuned to the minimum of the standing wave ratio by changing the configuration of the lower part of the frame ("loop"): by drawing closer or removing its conductors and selecting its length A A '. The initial value of the distance between the upper ends of the "loop" is 1.2 meters.

It is advisable to apply a waterproof coating on a wooden mast; the dielectric for the support insulator must be non-hygroscopic. The upper part of the frame is attached to the mast through: a support insulator. Insulators must also be inserted into the web of guy wires (5-6 pieces for each).

From the UX2LL website

Dipole 80 meters from UR5ERI

Victor has been using this antenna for three months now and is very happy with it. It is stretched like a normal dipole and it responds well to this antenna from all sides, this antenna only works at 80 m. variable capacity and measure it and put in a constant capacity to avoid headaches with sealing variable capacity.

From the UX2LL website

Antenna for 40 meters with a low suspension height

Igor UR5EFX, Dnepropetrovsk.

Loop antenna "DELTA LOOP", located in such a way that its upper corner is at a height of a quarter of a wave above the earth's surface, and power is supplied to the loop break in one of the lower corners, has a high level of radiation of a vertically polarized wave at a low level, about 25-35 ° angle relative to the horizon, which allows it to be used for long-distance radio communications.

A similar emitter was built by the author, and its optimal dimensions for the 7 MHz range are shown in Fig. The input impedance of the antenna, measured at 7.02 MHz, is 160 Ohm, therefore, for optimal matching with the transmitter (TX) having an output impedance of 75 Ohm, a matching device of two series-connected quarter-wave transformers from 75 and 50 Ohm coaxial cables was used (Fig. 2). The antenna impedance is converted first to 35 ohms, then to 70 ohms. In this case, the VSWR does not exceed 1.2. If the antenna is more than 10 ... 14 meters away from TX, to points 1 and 2 in Fig. you can connect a coaxial cable with a characteristic impedance of 75 ohms of the required length. Shown in fig. the dimensions of quarter-wave transformers are correct for PE-insulated cables (shortening factor 0.66). The antenna was tested with an 8W ORP transmitter. Telegraph QSOs with radio amateurs from Australia, New Zealand and the United States confirmed the antenna's effectiveness on long haul routes.

Counterweights (two in a quarter-wave line for each range) lay directly on the roofing felt. In both versions in the bands 18 MHz, 21 MHz and 24 MHz SWR (SWR)< 1,2, в диапазонах 14 MHz и 28 MHz КСВ (SWR) < 1,5. Настройка антенны при смене диапазона крайне проста: вращать КПЕ до минимума КСВ. Я это делал руками, но ничто не мешает использовать КПЕ без ограничителя угла поворота и небольшой моторчик с редуктором (например от старого дисковода) для его вращения.

P.S. I made this antenna, but it is really acceptable, you can work, and work well. I used a device with an RD-09 motor, and made a friction clutch, i.e. so that when the plates are fully withdrawn and inserted, slipping occurs. The clutch discs are from an old reel to reel tape recorder. A three-section condenser, if the capacity of one section is not enough, you can always connect another one. Naturally, the whole structure is placed in a moisture-proof box. I post a photo, look - you will figure it out!

Antenna "Lazy Delta"

An antenna with a slightly odd name was published in the 1985 Radio Yearbook. It is depicted as an ordinary isosceles triangle with a perimeter of 41.4 m and, obviously, therefore, did not attract attention. As it turned out later, it was in vain. I just needed a simple multi-band antenna, and I suspended it at a low height - about 7 meters. The length of the supply cable RK-75 is about 56 m (half-wave repeater). The measured SWR values ​​practically coincided with those given in the Yearbook.

Coil L1 is wound on an insulating frame with a diameter of 45 mm and contains 6 turns of PEV-2 wire with a thickness of 2 ... 3 mm. HF transformer T1 is wound with MGSHV wire on a 400NN 60x30x15 mm ferrite ring, contains two windings of 12 turns each. The size of the ferrite ring is not critical and is selected based on the input power. The power cable is connected only as shown in the figure, if you turn it on the other way around, the antenna will not work.

The antenna does not require adjustment, the main thing is to accurately maintain its geometric dimensions. When working on a range of 80 m, in comparison with other simple antennas, it loses to transmit - the length is too small.

At the reception, the difference is practically not felt. Measurements carried out by G. Bragin's HF bridge ("R-D" No. 11) showed that we are dealing with a non-resonant antenna. The frequency response meter only shows the resonance of the power cable. It can be assumed that a fairly universal antenna (from simple ones) has turned out, has small geometric dimensions and its SWR practically does not depend on the suspension height. Then it became possible to increase the suspension height up to 13 meters above the ground. And in this case, the SWR value for all the main amateur bands, except for the 80-meter one, did not exceed 1.4. At the eighties, its value ranged from 3 to 3.5 at the upper frequency of the range, therefore, a simple antenna tuner is additionally used to match it. Later we managed to measure SWR on the WARC bands. There the VSWR value did not exceed 1.3. Antenna drawing is shown in the figure.

V. Gladkov, RW4HDK Chapayevsk

Http://ra9we.narod.ru/

Antenna Inverted V - Windom

For almost 90 years now, radio amateurs have been using the Windom antenna, which got its name from the name of the American shortwave who proposed it. Coaxial cables were rare in those days, and he figured out how to power a half-wavelength emitter with a single wire feeder.

It turned out that this can be done if the antenna feeding point (connecting a single-wire feeder) is taken at a distance of about one third from the end of the radiator. The input impedance at this point will be close to the characteristic impedance of such a feeder, which in this case will operate in a mode close to that of a traveling wave.

The idea turned out to be fruitful. At the time, the six amateur bands in use were multiples (not multiples of the WARC bands only appeared in the 1970s), and this point proved to be suitable for them as well. Not a perfect point, but perfectly acceptable for amateur practice. Over time, many variants of this antenna appeared, designed for different bands, with the general name OCF (off-center fed - with power not in the center).

Here it was first described in detail in the article by I. Zherebtsov "Transmitting antennas powered by a traveling wave", published in the journal "Radiofront" (1934, No. 9-10). After the war, when coaxial cables became part of amateur radio practice, a convenient power supply option appeared for such a multi-band emitter. The fact is that the input impedance of such an antenna on the operating ranges is not very different from 300 Ohm. This allows the use of common coaxial feeders with a characteristic impedance of 50 and 75 Ohm for its power supply through HF transformers with a transformation ratio of 4: 1 and 6: 1 impedance. In other words, this antenna easily entered everyday radio amateur practice in the post-war years. Moreover, it is still mass-produced for shortwave (in various versions) in many countries of the world.

It is convenient to hang the antenna between houses or two masts, which is not always acceptable due to the real circumstances of housing both in the city and outside the city. And, of course, over time, an option appeared to install such an antenna using only one mast, which is more realistic to use in a residential building. This variant was named Inverted V - Windom.

The Japanese shortwave JA7KPT, apparently, was one of the first to use this option for installing an antenna with a radiator length of 41 m. This radiator length was supposed to provide it with operation at 3.5 MHz and higher HF bands. He used a mast 11 meters high, which is the maximum size for most radio amateurs to install a makeshift mast on a residential building.

The radio amateur LZ2NW (http: // lz2zk.bfra.bg/antennas/page1 20 / index.html) repeated his version of Inverted V - Windom. Its antenna is schematically shown in Fig. 1. The height of the mast was about the same (10.4 m), and the ends of the radiator were about 1.5 m from the ground. To power the antenna, a coaxial feeder with a characteristic impedance of 50 Ohm and a transformer (BALUN) with a coefficient 4: 1 transformation.

Rice. 1. Antenna diagram

The authors of some variants of the Windom antenna note that it is more expedient to use a transformer with a transformation ratio of 6: 1 when the characteristic impedance of the feeder is 50 Ohm. But most of the antennas are still made by their authors with 4: 1 transformers for two reasons. Firstly, in a multi-band antenna, the input impedance “walks” within certain limits near the value of 300 ohms, therefore, the optimal values ​​of the transformation ratios will always differ slightly on different ranges. Secondly, the 6: 1 transformer is more difficult to manufacture, and the benefits from its use are not obvious.

The LZ2NW achieved VSWR values ​​less than 2 (1.5 typical) using a 38m feeder on virtually all amateur bands. For JA7KPT, the results are close, but for some reason its VSWR range fell out in the 21 MHz range, where it was greater than 3. Since the antennas were not installed in a “clear field”, such a dropout on a specific range may be due, for example, to the influence of the surrounding “ gland".

LZ2NW used an easy-to-manufacture BALUN, made on two ferrite rods with a diameter of 10 and a length of 90 mm from the antennas of a household radio receiver. Each rod is wound in two wires, ten turns of a wire with a diameter of 0.8 mm in PVC insulation (Fig. 2). And the resulting four windings are connected in accordance with Fig. 3. Of course, such a transformer is not intended for powerful radio stations - up to an output power of 100 W, no more.

Rice. 2.PVC insulation

Rice. 3. Winding connection diagram

Sometimes, if the specific situation on the roof permits, the Inverted V - Windom antenna is made asymmetrical, fixing the BALUN at the top of the mast. The advantages of this option are clear - in bad weather, snow and ice, settling on the BALUN antenna hanging on the wire, can cut it off.

B. Stepanov's material

Compactantenna for the main HF bands (20 and 40 m) - for summer cottages, trips and hikes

In practice, many radio amateurs, especially in summer, often need a simple temporary antenna for the most basic HF bands - 20 and 40 meters. In addition, the place for its installation can be limited, for example, by the size of the summer cottage or in the field (on a fishing trip, on a hike - by the river) by the distance between the trees that are supposed to be used for this.

To reduce its size, a well-known technique was used - the ends of the 40-meter range dipole are turned towards the center of the antenna and are located along its canvas. Calculations show that the characteristics of the dipole change insignificantly in this case, if the segments subjected to this modification are not very long in comparison with the operating wavelength. As a result, the overall length of the antenna is reduced by almost 5 meters, which in certain conditions can be a decisive factor.

To introduce the second band into the antenna, the author used a method that is called "Skeleton Sleeve" or "Open Sleeve" in the English-language radio amateur literature. Its essence is that the emitter for the second band is placed next to the emitter of the first band, to which the feeder is connected.

But the additional emitter does not have a galvanic connection with the main one. Such a design can significantly simplify the design of the antenna. The length of the second element determines the second working range, and its distance to the main element determines the radiation resistance.

In the described antenna for the emitter of the range of 40 meters, mainly the lower (according to Fig. 1) conductor of a two-wire line and two sections of the upper conductor are used. At the ends of the line, they are soldered to the bottom conductor. The emitter of the range of 20 meters is formed by a simple cut of the upper conductor

The feeder is made of RG-58C / U coaxial cable. Near the point of its connection to the antenna there is a choke - current BALUN ", the design of which can be taken from. Its parameters are more than sufficient to suppress the common-mode current along the outer sheath of the cable on the ranges of 20 and 40 meters.

The results of calculating the antenna directional patterns. executed in the EZNEC program are shown in Fig. 2.

They are calculated for an antenna installation height of 9 m. The red color shows the radiation pattern for a range of 40 meters (frequency 7150 kHz). The gain at the maximum of the diagram in this range is 6.6 dBi.

The radiation pattern for a range of 20 meters (frequency 14150 kHz) is shown in blue. In this range, the gain at the maximum of the diagram is 8.3 dBi. This is even 1.5 dB more than that of a half-wave dipole and is due to the narrowing of the radiation pattern (by about 4 ... 5 degrees) compared to the dipole. Antenna SWR does not exceed 2 in the frequency bands of 7000 ... 7300 kHz and 14000 ... 14350 kHz.

For the manufacture of the antenna, the author used a two-wire line of the American company JSC WIRE & CABLE, the conductors of which are made of steel coated with copper. This provides sufficient mechanical strength for the antenna.

Here you can use, for example, the more common similar line MFJ-18H250 from the well-known American company MFJ Enterprises.

The external view of this dual-band antenna, stretched between trees on the river bank, is shown in Fig. 3.

The only disadvantage is that it can be really used as a temporary one (in the country or in the field) in spring-summer-autumn. It has a relatively large surface area (due to the use of a ribbon cable), so it is unlikely that it will carry the load from adhered snow or ice in winter.

Literature:

1. Joel R. Hallas A Folded Skeleton Sleeve Dipole for 40 and 20 Meters. - QST, 2011, May, p. 58-60.

2. Martin Steyer The Construction Principles for "open-sleeve" -Elements. - http://www.mydarc.de/dk7zb/Duoband/open-sleeve.htm.

3. Stepanov B. BALUN for KB antenna. - Radio, 2012, No. 2, p. 58

A selection of broadband antenna designs

Happy viewing!

Today, when most of the old housing stock has been privatized, and the new one is certainly private property, it becomes more and more difficult for radio amateurs to install full-size antennas on the roof of their house. The roof of a residential building is part of the property of every inhabitant of the house where they live, and they will never allow you to walk on it again, and even more so to install some kind of antenna and spoil the facade of the building. Nevertheless, today there are such cases when a radio amateur enters into an agreement with a housing department for the lease of a part of the roof with his antenna, but this requires additional financial resources and this is a completely different topic. Therefore, many novice radio amateurs can afford only those antennas that can be installed on a balcony or loggia, risking a reprimand from the house manager for damaging the facade of the building with an absurd protruding structure.

Pray to God that some "know-it-all activist" does not give a hint about the harmful radiation of the antenna, as from cellular antennas. Unfortunately, it must be admitted that for radio amateurs a new era of secrecy of their hobby and their HF antennas has begun, despite the paradox of their legality in the legal aspect of this issue. That is, the state allows broadcasting on the basis of the "Law on Communications of the Russian Federation", and the levels of permitted power correspond to the standards for HF radiation SanPiN 2.2.4 / 2.1.8.055-96, but they have to be invisible in order to avoid pointless evidence of the legality of their activities.

The proposed material will help the radio amateur to understand the antennas with a large shortening, capable of being placed in the space of a balcony, loggia, on the wall of a residential building or in a limited antenna field. The article "HF Balcony Antennas for Beginners" provides an overview of the options for antennas by different authors, previously published both in paper and electronic form, and selected for the conditions of their installation in a limited space.

The explanatory comments will help the beginner understand how the antenna works. The presented materials are aimed at novice radio amateurs to acquire skills in building and choosing mini-antennas.

1. Dipole Hertz.
2. Shortened Hertzian dipole.
3. Spiral antennas.
4. Magnetic antennas.
5. Capacitive antennas.

1. Hertz's dipole

The most classic type of antenna is undeniably the Hertz dipole. This is a long wire, most often with a half-wave antenna width. Antenna wire has its own capacitance and inductance, which are distributed over the entire antenna web, they are called distributed antenna parameters. The capacitance of the antenna creates the electric component of the field (E), and the inductive component of the antenna, the magnetic field (H).

The classic Hertzian dipole by its nature has impressive dimensions and is half a long wave. Judge for yourself, at a frequency of 7 MHz, the wavelength is 300/7 = 42.86 meters, and half a wave will be 21.43 meters! Important parameters of any antenna are its characteristics from the side of space, these are its aperture, radiation resistance, effective antenna height, radiation pattern, etc., as well as from the side of the feeding feeder, these are input impedance, the presence of reactive components and the interaction of the feeder with the emitted wave. A half-wave dipole is a widespread linear emitter in the practice of antenna technology. However, any antenna has its own advantages and disadvantages.

Immediately, we note that for good operation of any antenna, at least two conditions are required, this is the presence of an optimal bias current and effective formation of an electromagnetic wave. HF antennas can be either vertical or horizontal. By installing a half-wave dipole vertically, and reducing its height by turning the fourth part into counterweights, we get the so-called quarter-wave vertical. Vertical quarter-wave antennas, for their effective operation, require a good "radio-technical ground", tk. the soil of the planet "Earth" has poor conductivity. The radio engineering ground is replaced by connecting counterweights. Practice shows that the minimum required number of counterweights should be about 12, but it is better if their number exceeds 20 ... 30, and ideally it is necessary to have 100-120 counterweights.

It should never be forgotten that an ideal vertical antenna with a hundred counterweights has an efficiency of 47%, and an antenna with three counterweights has an efficiency of less than 5%, which is clearly reflected in the graph. The power supplied to an antenna with a small number of counterweights is absorbed by the earth's surface and surrounding objects, heating them. The same low efficiency is expected with a low horizontal vibrator. Simply put, the earth reflects poorly and absorbs well the radiated radio wave, especially when the wave has not yet been formed in the near zone from the antenna, like a clouded mirror. The sea surface reflects better and the sandy desert does not reflect at all. According to the theory of reciprocity, the parameters and characteristics of the antenna are the same for both reception and transmission. This means that in the receiving mode at the vertical with a small number of counterweights, large losses of the useful signal occur and, as a consequence, an increase in the noise component of the received signal.

Counterweights of a classic vertical should be at least as long as the main pin, i.e. The displacement currents flowing between the pin and the counterweights occupy a certain volume of space, which is involved not only in the formation of the directional diagram, but also in the formation of the field strength. With a greater approximation, we can say that each point on the pin corresponds to its own mirror point on the counterweight, between which displacement currents flow. The fact is that displacement currents, like all ordinary currents, flow along the path of least resistance, which in this case is concentrated in a volume limited by the radius of the pin. The generated directional diagram will be the superposition (superposition) of these currents. Returning to the above, this means that the efficiency of a classical antenna depends on the number of counterweights, i.e. the more counterweights, the more bias current, the more efficient the antenna, THIS IS THE FIRST CONDITION for good antenna performance.

The ideal case is a half-wave vibrator located in an open space in the absence of absorbing soil, or a vertical located on a solid metal surface with a radius of 2-3 wavelengths. This is necessary so that the soil of the earth or the objects surrounding the antenna do not interfere with the effective formation of the electromagnetic wave. The fact is that the formation of a wave and the phase coincidence of the magnetic (H) and electric (E) components of the electromagnetic field occurs not in the near zone of the Hertz dipole, but in the middle and far zone at a distance of 2-3 wavelengths, THIS IS THE SECOND CONDITION for good work antennas. This is the main disadvantage of the classical Hertzian dipole.

The generated electromagnetic wave in the far zone is less susceptible to the influence of the earth's surface, bends around it, is reflected and propagates in the medium. All of the above very brief concepts are needed in order to understand the further essence of the construction of amateur balcony antennas, to look for such an antenna construct in which a wave is formed inside the antenna itself.

It is now clear that the placement of full-size antennas, a quarter-wave pole with counterweights or a half-wave Hertzian dipole in the HF range is almost impossible to place within a balcony or loggia. And if the radio amateur managed to find an accessible antenna attachment point on the building opposite to the balcony or window, then today it is considered great luck.

2. Shortened Hertzian dipole.

With limited space at their disposal, the radio amateur has to compromise and reduce the size of the antennas. Antennas are considered electrically small if their dimensions do not exceed 10 ... 20% of the wavelength λ. In such cases, a shortened dipole is often used. When the antenna is shortened, its distributed capacitance and inductance decrease, respectively, its resonance changes towards higher frequencies. To compensate for this deficiency, additional inductors L and capacitive loads C are introduced into the antenna as lumped elements (Fig. 1).

The maximum antenna efficiency is achievable by placing the extension coils at the ends of the dipole, since the current at the ends of the dipole is maximum and distributed more evenly, which ensures the maximum effective antenna height hd = h. Turning on the inductors closer to the center of the dipole will reduce its own inductance, in this case the current to the ends of the dipole drops, the effective height decreases, and then the antenna efficiency.

What is a capacitive load in a shortened dipole for? The fact is that with a large shortening, the quality factor of the antenna increases greatly, and the bandwidth of the antenna becomes narrower than the radio amateur band. The introduction of capacitive loads increases the antenna capacity, reduces the Q-factor of the formed LC-circuit and expands its bandwidth to an acceptable level. A shortened dipole is tuned to the operating frequency in resonance either by inductors or by the length of the conductors and capacitive loads. This provides compensation for their reactances at the resonant frequency, which is necessary according to the conditions of coordination with the power feeder.

Note: Thus, we compensate for the necessary characteristics of the shortened antenna to match it with the feeder and space, but a decrease in its geometric dimensions ALWAYS leads to a decrease in its efficiency (efficiency).

One of the examples of calculating the extension coil of inductance was available in the calculation in the Journal "Radio", number 5, 1999, where the calculation is carried out from the available emitter. Inductors L1 and L2 are located here at the feeding point of the quarter-wave dipole A and counterweight D (Fig. 2). This is a single band antenna.

You can also calculate the inductance of the shortened dipole on the site of the radio amateur RN6LLV - he gives a link to download a calculator that can help in calculating the lengthening inductance.

There are also branded shortened antennas (Diamond HFV5), which have a multi-band version, see Fig. 3, in the same place its electrical diagram.

Antenna operation is based on parallel connection of resonant elements tuned to different frequencies. When moving from one range to another, they practically do not affect each other. Inductors L1-L5 are extension coils, each designed for its own frequency range, just like capacitive loads (continuation of the antenna). The latter have a telescopic design, and by changing their length they are able to adjust the antenna in a small frequency range. The antenna is very narrow band.

* Mini - antenna for a range of 27MHz, the author of which is S. Zaugolny. Let's consider its work in more detail. The author's antenna is located on the 4th floor of a 9-storey panel building in the window opening and is essentially a room antenna, although this version of the antenna will work better outside the window (balcony, loggia) perimeter. As can be seen from the figure, the antenna consists of an oscillatory circuit L1C1, tuned to resonance to the frequency of the communication channel, and the communication coil L2 serves as a matching element with the feeder, Fig. 4.a. The main emitter here are capacitive loads in the form of wire frames with dimensions 300 * 300mm and a shortened symmetrical dipole consisting of two pieces of wire 750mm each. Considering that a vertically located half-wave dipole would occupy a height of 5.5 m, then an antenna with a height of only 1.5 m is a very convenient option for placement in the window opening.

If we exclude the resonant circuit from the circuit and connect the coaxial cable directly to the dipole, then the resonant frequency will be in the range of 55-60 MHz. Based on this scheme, it is clear that the frequency-setting element in this design is an oscillatory circuit, and the antenna is shortened by 3.7 times and has not greatly reduced its efficiency. If in this design an oscillating circuit tuned to other lower frequencies in the HF range is used, of course the antenna will work, but with much lower efficiency. For example, if such an antenna is tuned to 7 MHz of the amateur band, then the antenna shortening factor from half the wave of this range will be 14.3, and the antenna efficiency will drop even more (by the square root of 14), i.e. more than 200 times. But there is nothing to be done about this, you have to choose such an antenna design that would be as effective as possible. This design clearly shows that capacitive loads in the form of wire squares act as radiating elements here, and they would perform their functions if they were all-metal. The weak link here is the L1C1 oscillatory circuit, which must have a high Q-factor, and part of the useful energy in this design is uselessly spent inside the plates of the C1 capacitor. Therefore, an increase in the capacitance of a capacitor, although it reduces the resonance frequency, but it also reduces the overall efficiency of this design. When designing this antenna for lower frequencies in the HF range, you should pay attention to the fact that at the resonant frequency L1 is maximum, and C1 is minimum, not forgetting that capacitive radiators are part of the resonant system as a whole. It is advisable to design the maximum overlap in frequency no more than 2, and the emitters were located as far as possible from the walls of the building. The balcony version of this antenna with camouflage from prying eyes is shown in Fig. 4.b. It was a similar antenna that was used for some time in the middle of the 20th century on military vehicles in the HF range with a tuning frequency of 2-12 MHz.

* Single-band option "Non-dying Fuchs antenna"(21 MHz) is shown in Fig. 5.a. The 6.3 meter long (almost half-wave) rod is fed from the end by a parallel oscillatory circuit with the same high resistance. Mr. Fuchs decided that this is how the parallel oscillatory circuit L1C1 and the half-wave dipole agree with each other, the way it is ... As you know, the half-wave dipole is self-sufficient and works for itself, it does not need counterweights like a quarter-wave vibrator. The emitter (copper wire) can be placed in a plastic fishing rod. While working on the air, such a fishing rod can be moved out of the balcony railing and put back, but in winter this creates a number of inconveniences. A piece of wire of only 0.8 m is used as a "ground" for the oscillatory circuit, which is very convenient when placing such an antenna on a balcony. At the same time, this is an exceptional case when a flower pot can be used as grounding (just kidding). The inductance of the L2 resonant coil is 1.4 μH, it is made on a frame with a diameter of 48 mm and contains 5 turns of 2.4 mm wire with a pitch of 2.4 mm. As a resonant capacitor with a capacity of 40 pF, the circuit uses two pieces of RG-6 coaxial cable. The segment (C2 according to the scheme) is an unchanged part of the resonant capacitor with a length of no more than 55-60 cm, and a shorter segment (C1 according to the scheme) is used for fine tuning to resonance (15-20 cm). The L1 coupling coil in the form of one turn over the L2 coil is made with an RG-6 cable with a gap of 2-3 cm of its braid, and the SWR adjustment is carried out by moving this turn from the middle towards the counterweight.

Note: The Fuchs antenna works well only in the half-wave version of the emitter, which can be shortened like spiral antennas (read below).

* Multi-band balcony antenna option shown in Fig. 5 B. It was tested back in the 50s of the last century. Here the inductance acts as an extension coil in autotransformer mode. And the capacitor C1 at 14 MHz tunes the antenna into resonance. Such a pin requires a good grounding, which is difficult to find on the balcony, although for this option you can use an extensive network of heating pipes in your apartment, but it is not recommended to supply more than 50 W of power. Inductor L1 has 34 turns of 6mm diameter copper tube wound on a 70mm diameter frame. Taps from 2,3 and 4 turns. In the range of 21 MHz, the switch P1 is closed, P2 is open, In the range of 14 MHz, P1 and P2 are closed. At 7 MHz, the position of the switches is at 21 MHz. In the range of 3.5 MHz, P1 and P2 are open. Switch P3 determines the coordination with the feeder. In both cases, it is possible to use a rod of about 5m, then the rest of the emitter will hang to the ground. It is clear that the use of such antenna options should be higher than the 2nd floor of the building.

Not all examples of shortening dipole antennas are presented in this section; other examples of shortening a linear dipole will be presented below.

3. Spiral antennas.

Continuing the discussion of the topic of shortened balcony antennas, one cannot ignore the HF helical antennas. And of course, it is necessary to recall their properties, which have practically all the properties of a Hertzian dipole.

Any shortened antenna, the dimensions of which do not exceed 10-20% of the wavelength, are classified as electrically small antennas.

Features of small antennas:

1. The smaller the antenna, the less the ohmic loss should be in it. Small antennas assembled from thin wires cannot work effectively, since they experience increased currents, and the skin effect requires low surface resistances. This is especially true for antennas with radiator sizes significantly less than a quarter of the wavelength.
2. Since the field strength is inversely proportional to the size of the antenna, a decrease in the size of the antenna leads to an increase in very high field strengths near it, and with an increase in the input power leads to the appearance of the "St. Elmo's fire" effect.
3. The lines of force of the electric field of shortened antennas have a certain effective volume in which this field is concentrated. It has a shape close to an ellipsoid of revolution. In essence, this is the volume of the near quasi-static field of the antenna.
4. A small antenna with dimensions of λ / 10 or less has a Q-factor of about 40-50 and a relative bandwidth of no more than 2%. Therefore, in such antennas it is necessary to introduce an adjustment element within the same amateur band. Such an example is easy to observe with small magnetic antennas. Expanding the bandwidth reduces the efficiency of the antenna, therefore, you must always strive to increase the efficiency of ultra-small antennas in different ways.

* Reducing the size of a symmetric half-wave dipole led first to the appearance of extension coils (Fig. 6a), and a decrease in its turn-to-turn capacitance and a maximum increase in efficiency led to the appearance of an inductance coil for the design of helical antennas with transverse radiation. The spiral antenna (Fig. 6.b.) is a shortened, coiled classical half-wave (quarter-wave) dipole with distributed inductances and capacitors along the entire length. The Q-factor of such a dipole has increased, and the bandwidth has become narrower.

To expand the bandwidth, a shortened spiral dipole, like a shortened linear dipole, is sometimes equipped with a capacitive load, Fig. 6.b.

Since in the calculations of single-vibration antennas, the concept of the effective antenna area (A eff.) Is practiced quite widely, we will consider the possibilities of increasing the efficiency of spiral antennas using end disks (capacitive load) and refer to the graphical example of the distribution of currents in Fig. 7. Due to the fact that in a classical spiral antenna the inductance coil (rolled antenna web) is distributed along the entire length, the current distribution along the antenna is linear, and the current area increases insignificantly. Where, Iap is the antinode current of the spiral antenna, Fig. 7.a. And the effective area of ​​the antenna Aeff. determines that part of the plane wave front area from which the antenna picks up energy.

To expand the bandwidth and increase the effective radiation area, the installation of end discs is practiced, which increases the efficiency of the antenna as a whole, Fig. 7.b.

When it comes to single-ended (quarter-wave) helical antennas, you should always remember that Aeff. highly dependent on the quality of the land. Therefore, you should know that the same efficiency of a quarter-wave vertical is provided by four counterweights with a length of λ / 4, six counterweights with a length of λ / 8 and eight counterweights with a length of λ / 16. Moreover, twenty λ / 16 counterweights provide the same efficiency as eight λ / 4 counterweights. It becomes clear why balcony radio amateurs came to the half-wave dipole. It works for itself (see Fig. 7.c.), the lines of force are closed to their elements and "ground", as in the structures in Fig. 7.a; b. he doesn't need it. In addition, spiral antennas can also be equipped with lumped elements of extension-L (or shortening-C) of the electrical length of the spiral radiator, and their spiral length can differ from the full-size spiral. An example of this is a variable-capacity capacitor (discussed below), which can be considered not only as a tuning element for a sequential oscillatory circuit, but also as a shortening element. Also, a spiral antenna for portable stations in the 27 MHz range (Fig. 8). There is a short coil extension inductor here.

* Compromise solution can be seen in the design of Valery Prodanov (UR5WCA), - a balcony spiral antenna 40-20m with a shortening factor K = 14, is quite worthy of attention of radio amateurs without a roof, see Fig. 9.

Firstly, it is multi-band (7/10/14 MHz), and secondly, to increase its efficiency, the author doubled the number of spiral antennas and connected them in phase. The absence of capacitive loads in this antenna is due to the fact that the expansion of the bandwidth and Aeff. The antenna is achieved by in-phase connection of two identical radiation elements in parallel. Each antenna is wound with copper wire on a PVC pipe with a diameter of 5 cm, the length of the wire of each antenna is half a wave for the 7 MHz band. Unlike the Fuchs antenna, this antenna is matched to the feeder by means of a broadband transformer. The output of transformer 1 and 2 has a common-mode voltage. Vibrators in the author's version stand from each other at a distance of only 1m, this is the width of the balcony. With the expansion of this distance within the balcony, the gain will increase slightly, but the bandwidth of the antenna will expand significantly.

* Amateur radio Harry Elington(WA0WHE, source "QST", 1972, January. Fig. 8.) built an 80m spiral antenna with a shortening factor of about K = 6.7, which in its garden can be disguised as the support of a night lamp or flagpole. As you can see from his commentary, foreign radio amateurs also care about their relative peace of mind, although the antenna is installed in a private courtyard. According to the author, a spiral antenna with a capacitive load on a pipe with a diameter of 102 mm, a height of about 6 meters and a counterweight of four wires easily reaches an SWR of 1.2-1.3, and with SWR = 2 it works in a bandwidth of up to 100 kHz. The electrical length of the wire in the spiral was also half a wave. The half-wave antenna is powered from the end of the antenna through a coaxial cable with a characteristic impedance of 50 Ohm through a KPE -150pF, which turned the antenna into a series oscillatory circuit (L1C1) with a radiating coil inductance.

Of course, in transmission efficiency, the vertical spiral is inferior to the classical dipole, but according to the author, this antenna is much better in reception.

* Rolled up antennas

To reduce the size of a linear half-wave dipole, it is not necessary to twist it into a spiral.

In principle, the spiral can be replaced with other forms of folding of a half-wave dipole, for example, according to Minkowski, Fig. 11. A dipole with a fixed frequency of 28.5 MHz can be placed on a substrate with dimensions of 175 mm x 175 mm. But fractal antennas are very narrowband, and for radio amateurs they are only of cognitive interest in transforming their designs.

Using another method of shortening the size of the antennas, the half-wave vibrator, or the vertical, can be shortened by squeezing it into a meander shape, Fig. 12. In this case, the parameters of an antenna such as a vertical or a dipole change insignificantly when they are compressed by no more than half. When the horizontal and vertical parts of the meander are equal, the gain of the meander antenna is reduced by about 1 dB, and the input impedance is close to 50 Ohm, which makes it possible to feed such an antenna directly with a 50-ohm cable. A further reduction in size (NOT the length of the wire) leads to a decrease in the gain and input impedance of the antenna. However, the performance of a meander antenna for shortwave range is characterized by an increased radiation resistance relative to linear antennas with the same shortening of the wire. Experimental studies have shown that with a meander height of 44 cm and with 21 elements at a resonance frequency of 21.1 MHz, the antenna impedance was 22 Ohm, while a linear vertical of the same length has an impedance 10-15 times less. Due to the presence of horizontal and vertical sections of the meander, the antenna receives and emits electromagnetic waves of both horizontal and vertical polarization.

By squeezing or stretching it, you can achieve the antenna resonance at the desired frequency. The meander step can be 0.015λ, but this parameter is not critical. Instead of a meander, you can use a conductor with triangular bends or a spiral. The required length of the vibrators can be determined experimentally. As a starting point, we can assume that the length of the "straightened" conductor should be about a quarter of the wavelength for each arm of the split vibrator.

* "Tesla Spiral" in the balcony antenna. Following the cherished goal of reducing the size of the balcony antenna and minimizing the loss in Aeff, radio amateurs instead of end disks began to use a more technologically advanced flat Tesla spiral than the meander, using it as an extension of the inductance of the shortened dipole and the end capacitance at the same time (Fig. 6. a.). The distribution of magnetic and electric fields in a flat Tesla inductor is shown in Fig. 13. This corresponds to the theory of radio wave propagation, where the E-field and the H-field are mutually perpendicular.

There is also nothing supernatural in antennas with two flat Tesla spirals, and therefore the rules for constructing a Tesla spiral antenna remain classic:

• the electrical length of the spiral can be an antenna with an unbalanced power supply, either a quarter-wave vertical or a folded half-wave dipole.
• The larger the winding step and the larger its diameter, the higher its efficiency and vice versa.
• The greater the distance between the ends of the folded half-wave vibrator, the higher its efficiency, and vice versa.

In a word, we got a rolled half-wave dipole in the form of flat inductors at its ends, see Fig. 14. To what extent to reduce or increase this or that structure, the radio amateur decides after going out to his balcony with a tape measure (after agreement with the last instance, with his mother or wife).

Using a flat inductor with large gaps between the turns at the ends of the dipole, two problems are solved at once. This is the compensation of the electrical length of the shortened vibrator by the distributed inductance and capacitance, as well as the increase in the effective area of ​​the shortened antenna Aeff, and the expansion of its bandwidth simultaneously, as in Fig. 7.b.c. This solution simplifies the design of the shortened antenna and allows all dispersed LC antenna elements to operate at maximum efficiency. There are no non-working antenna elements, for example, as a capacitance in magnetic ML-antennas, and inductance in EH-antennas. It should be remembered that the skin effect of the latter requires thick and highly conductive surfaces, but considering an antenna with a Tesla coil, we see that a coiled antenna repeats the electrical parameters of a conventional half-wave vibrator. In this case, the distribution of currents and voltages along its entire length of the antenna web is subject to the laws of a linear dipole and remains unchanged with some exceptions. Therefore, the need to thicken the antenna elements (Tesla spiral) completely disappears. In addition, power is not consumed for heating the antenna elements. The facts listed above make you think about the high budget of this design. And the simplicity of its manufacture from the hand to someone who at least once in his life held a hammer in his hands and bandaged his finger.

Such an antenna with some interference can be called inductively capacitive, in which there are LC radiation elements, or a Tesla spiral antenna. In addition, taking into account the near field (quasi-static) theoretically can give even higher values ​​of the strengths, which is confirmed by field tests of this design. The EH-field is created in the body of the antenna and, accordingly, this antenna is less dependent on the quality of the ground and surrounding objects, which in fact is a godsend for the family of balcony antennas. It is no secret that such antennas have long existed among radio amateurs, and this publication provides material on transforming a linear dipole into a spiral antenna with transverse radiation, then into a shortened antenna with the code name "Tesla spiral". A flat spiral can be wound with a wire of 1.0-1.5mm, because high voltage is present at the end of the antenna and the current is minimal. A wire with a diameter of 2-3mm will slightly improve the efficiency of the antenna, but it will significantly drain your wallet.

Note: Design and manufacture of shortened "spiral" and "Tesla spiral" antennas with electrical length λ / 2 compares favorably with a spiral with electrical length λ / 4 due to the lack of good ground on the balcony.

Antenna power supply.

We consider an antenna with Tesla spirals as a symmetrical half-wave dipole, coiled into two parallel spirals at its ends. Their planes are parallel to each other, although they can be in the same plane, Fig. 14. Its input impedance is only slightly different from the classic version, so the classic matching options are applicable here.

Linear Windom antenna see Fig. 15. refers to vibrators with unbalanced power supply, it is distinguished by its "unpretentiousness" in terms of matching with the transceiver. The uniqueness of the Windom antenna lies in its multi-band application and ease of manufacture. Converting this antenna into "Tesla spirals", in space, the symmetrical antenna will look like in Fig. 16.а, - with gamma-matching, and an asymmetric dipole Windom, fig.16.b.

To decide which antenna option to choose to implement your plans to turn your balcony into an "antenna field" is better to read this article to the end. The design of balcony antennas compares favorably with full-size antennas in that their parameters and other combinations can be made without leaving the roof of your house and not injuring the house manager once again. In addition, this antenna is a practical guide for novice radio amateurs, when you can practically "on your knees" learn all the basics of building elementary antennas.

Antenna assembly

Based on practice, it is better to take the length of the wire that makes up the antenna web with a small margin, slightly larger by 5-10% of its estimated length, it should be an insulated single-core copper wire for electrical installation with a diameter of 1.0-1.5 mm. The supporting structure of the future antenna is assembled (by soldering) from PVC heating pipes. Of course, in no case should pipes with a reinforced aluminum pipe be used. Dry wooden sticks are also suitable for the experiment, see Fig. 17.

The Russian radio amateur does not need to tell the step-by-step assembly of the supporting structure, he just needs to look at the original product from afar. Nevertheless, when assembling a Windom antenna or a symmetrical dipole, it is worth first marking the calculated power point on the future antenna web and fixing it in the middle of the traverse, where the antenna will be powered. Naturally, the length of the traverse is included in the total electrical dimension of the future antenna, and the longer it is, the higher the antenna efficiency.

Transformer

The impedance of the symmetrical dipole antenna will be slightly less than 50 Ohm, therefore, the connection diagram, see Fig. 18.a. can be arranged by simply turning on the magnetic latch or using gamma matching.

The resistance of the rolled antenna "Windom" has a little less than 300 Ohm, so you can use the data in Table 1, which captivates with its versatility with the use of just one magnetic latch.

The ferrite core (latch) must be tested before installation on the antenna. To do this, the secondary L2 is connected to the transmitter, and the primary L1 to the antenna equivalent. They check the SWR, heating of the core, as well as the power loss in the transformer. If the core heats up at a given power, then the number of ferrite latches must be doubled. If there is an unacceptable loss in power, then ferrite must be selected. See Table 2 for the power loss to dB ratio.

As convenient as ferrite is, I still believe that for the radiated radio wave of any mini-antenna, where a huge EH-field is concentrated, it is a "black hole". The close location of the ferrite reduces the efficiency of the mini-antenna by a factor of µ / 100, and all attempts to make the antenna as efficient as possible are in vain. Therefore, in mini-antennas, the greatest preference is given to transformers with an air core, Fig. 18.b. Such a transformer, operating in the range of 160-10m, is wound with a double wire 1.5mm on a frame with a diameter of 25 and a length of 140mm, 16 turns with a winding length of 100mm.

It is also worth remembering that the feeder of such an antenna experiences a high intensity of the radiated field on its braid and creates a voltage in it, which negatively affects the operation of the transceiver in the transmission mode. It is better to eliminate the antenna effect with a locking feeder-choke without using ferrite rings, see Fig. 19. These are 5-20 turns of coaxial cable, wound on a frame with a diameter of 10-20 centimeters.

Such feeder chokes can be installed in the immediate vicinity of the antenna web (body), but it is better to go beyond the high field concentration limit and install at a distance of about 1.5-2m from the antenna web. A second such choke, installed at a distance of λ / 4 from the first, will not interfere.

Antenna tuning

Tuning the antenna brings great pleasure, and moreover, such a construct is recommended to be used for laboratory work in specialized colleges and universities, without leaving the laboratory, on the topic "Antennas".

Tuning can be started by searching for the resonance frequency and tuning the antenna SWR. It consists in moving the antenna feed point to one side or the other. It is not necessary to move the transformer or the supply cable along the traverse and mercilessly cut the wires to clarify the power point. Everything here is close and simple.

It is enough to make sliders in the form of "crocodiles" at the inner ends of the flat spirals on one side and on the other, as shown in Fig. 20. Having previously provided for slightly increasing the length of the spiral, taking into account the settings, we move the sliders from different sides of the dipole by the same length, but in opposite directions, thereby we move the feeding point. The result of the tuning will be the expected SWR of no more than 1.1-1.2 at the found frequency. Reactive components should be kept to a minimum. Of course, like any antenna, it should be located in a place as close as possible to the conditions of the installation site.

The second stage will be tuning the antenna exactly into resonance, this is achieved by shortening or lengthening the vibrators on both sides into equal pieces of wire with the same sliders. That is, you can increase the tuning frequency by shortening both turns of the spiral by the same size, and reduce the frequency, on the contrary, by lengthening. After completing the tuning at the future installation site, it is necessary to reliably connect, isolate and fix all antenna elements.

Antenna gain, bandwidth and beam angle

According to practicing radio amateurs, this antenna has a lower radiation angle of about 15 degrees than a full-size dipole and is more suitable for DX communications. The Tesla spiral dipole has an attenuation of -2.5 dB relative to a full-size dipole mounted at the same height from the ground (λ / 4). The bandwidth of the antenna at the level of -3 dB is 120-150 kHz! When placed horizontally, the described antenna has an eightfold radiation pattern similar to that of a full-size half-wave dipole, and the minima of the radiation pattern provide attenuation of up to -25 dB. The antenna efficiency can be improved, as in the classic version, by increasing the placement height. But when the antennas are placed under the same conditions at heights of λ / 8 and below, the Tesla spiral antenna will be more effective than a half-wave dipole.

Note: All these Tesla spiral antennas look perfect, but even if such an antenna layout is worse than a dipole by 6dB, i.e. one point on the S-meter, that's great.

Other antenna designs.

With a dipole for a range of 40 meters and with other designs of dipoles up to a range of 10m, everything is now clear, but let's return to the spiral vertical for a range of 80m (Fig. 10.). Here, preference is given to a half-wave helical antenna, and therefore "ground" is only needed nominally.

The power supply of such antennas can be carried out as in Fig. 9 by means of a summing transformer or in Fig. 10. variable capacitor. Of course, in the second case, the bandwidth of the antenna will be much narrower, but the antenna has the ability to tune in the range and yet, according to the copyright information, at least some kind of grounding is required. Our task is to get rid of it while on the balcony. Since the antenna is powered from the end (at the voltage "antinode"), the input impedance of a shortened half-wave helical antenna can be about 800-1000 ohms. This value depends on the height of the vertical part of the antenna, on the diameter of the "Tesla spiral" and on the location of the antenna relative to the surrounding objects. To match the high input impedance of the antenna with a low impedance of the feeder (50 Ohm), you can use a high-frequency autotransformer in the form of an inductor with a tap (Fig. 21.a), which is widely practiced in half-wave, vertically arranged linear antennas at 27 MHz by SIRIO, ENERGY, etc.

Data of the matching autotransformer for a half-wave antenna C-Bi of the 10-11m range:

D = 30mm; L1 = 2 turns; L2 = 5 turns; d = 1.0mm; h = 12-13 mm. Distance between L1 and L2 = 5mm. The coils are wound on one plastic frame coil to coil. The cable is connected with a central core to a 2-turn tap. The web (end) of the half-wave vibrator is connected to the "hot" lead of the L2 coil. The power for which the autotransformer is designed is up to 100 W. Possible selection of the retraction of the coil.

Data of the matching autotransformer for a half-wave antenna of the spiral type 40m range:

D = 32mm; L1 = 4.6μH; h = 20 mm; d = 1.5mm; n = 12 turns. L2 = 7.5μH; ; h = 27 mm; d = 1.5mm; n = 17 turns. The coil is wound on one plastic frame. The cable is connected with the central core to the tap. The antenna web (end of the helix) is connected to the hot lead of the L2 coil. The power for which the autotransformer is designed is 150-200W. Possible selection of the retraction of the coil.

Dimensions of the antenna "Tesla spiral" range 40m:the total length of the wire is 21m, the traverse is 0.9-1.5m high with a diameter of 31mm, on radially mounted spokes, 0.45m each. The outer diameter of the spiral will be 0.9m

Data of the matching autotransformer for the spiral antenna of the 80m range: D = 32mm; L1 = 10.8μH; h = 37 mm; d = 1.5mm; n = 22 turns. L2 = 17.6μH; ; h = 58 mm; d = 1.5mm; n = 34 turns. The coil is wound on one plastic frame. The cable is connected with the central core to the tap. The antenna web (end of the helix) is connected to the hot lead of the L2 coil. Possible selection of the retraction of the coil.

Dimensions of the antenna "Tesla spiral" range of 80m:the total length of the wire is 43m, the traverse is 1.3-1.5m high with a diameter of 31mm, on the radially installed spokes of 0.6m. The outer diameter of the spiral will be 1.2m

Matching with a half-wave spiral dipole when powered from the end can be carried out not only by means of an autotransformer, but also according to Fuchs, a parallel oscillatory circuit, see Fig. 5.a.

Note:

• When feeding a half-wave antenna from one end, tuning to resonance can be done from either end of the antenna.
• In the absence of at least some kind of grounding, a locking feeder-choke must be installed on the feeder.

Vertical directional antenna option

With a pair of Tesla spiral antennas and some area to accommodate them, you can create a directional antenna. Let me remind you that all operations with this antenna are completely identical with linear antennas, and the need to roll them up is not due to the fashion for mini-antennas, but to the lack of locations for linear antennas. The use of two-element directional antennas with a distance of 0.09-0.1λ between them makes it possible to design and build a directional Tesla spiral antenna.

This idea is taken from "KB JOURNAL" No. 6 for 1998. This antenna is perfectly described by Vladimir Polyakov (RA3AAE), which can be found on the Internet. The essence of the antenna is that two vertical antennas located at a distance of 0.09λ are fed in antiphase by one feeder (one with a braid, the other with a central core). Power is produced like the same Windom antenna, only with a single-wire power supply, Fig. 22 .. The phase shift between opposite antennas is created by tuning them lower and higher in frequency, as in classic directional Yagi antennas. And the coordination with the feeder is carried out by simply moving the feed point along the web of both antennas, moving away from the zero feed point (the middle of the vibrator). When you move the power point from the middle for a certain distance X, you can achieve resistance from 0 to 600 ohms as in the Windom antenna. We only need a resistance of about 25 ohms, so the displacement of the feed point from the middle of the vibrators will be very small.

The electrical diagram of the proposed antenna with approximate dimensions given in wavelengths is shown in Fig. 22. And the practical tuning of the Tesla spiral antenna to the required load resistance is quite feasible using the technology in Fig. 20. The antenna is powered at points XX directly by a feeder with a characteristic impedance of 50 Ohm, and its braid must be isolated with a blocking feeder-choke, see Fig. 19.

30m vertical directional helix antenna option according to RA3AAE

If for some reason the radio amateur is not satisfied with the version of the Tesla spiral antenna, then the version of the antenna with spiral radiators is quite feasible, Fig. 23. Let's give its calculation.

We use the length of the helix wire half a wave:

λ = 300 / MHz = 300 / 10.1; λ / 2 -29.7 / 2 = 14.85. Let's take 15m

Let's calculate the step on the coils on a pipe with a diameter of 7.5 cm, the length of the coil winding = 135 cm:

Circumference L = D * π = -7.5cm * 3.14 = 23.55cm. = 0.2355m;

number of turns of a half-wave dipole -15m / 0.2355 = 63.69 = 64 turns;

the step of winding on a ruby ​​with a length of 135cm. - 135cm. / 64 = 2.1cm ..

Answer: on a pipe with a diameter of 75 mm we wind 15 meters of copper wire with a diameter of 1-1.5 mm in the amount of 64 turns with a winding step = 2 cm.

The distance between the same vibrators will be 30 * 0.1 = 3m.

Note: the antenna calculations were rounded off for the possibility of shortening the winding wire during tuning.

To increase the bias current and ease of adjustment, it is necessary to make small adjustable capacitive loads at the ends of the vibrators, and a locking-feeder-choke must be put on the feeder, at the connection point. The displaced feed points correspond to the dimensions in Fig. 22. It should be remembered that unidirectionality in this design is achieved by a phase shift between opposite spirals by tuning them with a difference of 5-8% in frequency, as in classical directional Uda-Yagi antennas.

Rolled up "Bazooka"

As you know, the noise environment in any city leaves much to be desired. This also applies to the frequency radio spectrum due to the tatal use of impulse power converters for household appliances. For this reason, I made an attempt to use in the antenna "Tesla spiral" a well-proven antenna of the "Bazooka" type. In principle, this is the same half-wave vibrator with a closed-loop system as all loop antennas. It was not difficult to place it on the traverse presented above. The experiment was carried out at a frequency of 10.1 MHz. A 7mm TV cable was used as the antenna web. (fig. 24). The main thing is that the braid of the cable is not aluminum like its sheath, but copper.

Even experienced radio amateurs "pierce" on this, taking a gray cable braid for tinned copper when buying. Since we are talking here is a QRP antenna for a balcony, and the input power is up to 100 W, then such a cable will be quite suitable. The shortening factor of such a cable with foamed polyethylene is about 0.82. Therefore, the length of L1 (Fig. 25) for a frequency of 10.1 MHz. It was 7.42cm each, and the length of the extension conductors L2 with this antenna arrangement was 1.83cm each. The input resistance of the folded "Bazooka" after mounting in an open area was about 22-25 ohms and is not regulated by anything. Therefore, a 1: 2 transformer was required here. In the trial version, it was made on a ferrite latch with simple wires from speakers with the ratio of turns according to Table 1. Another version of the 1: 2 transformer is shown in Fig. 26.

Aperiodic broadband antenna "Bazooka"

Not a single radio amateur who even has an antenna field at his disposal on the roof of his house or in the courtyard of a cottage will refuse a broadband survey antenna based on a Tesla spiral feeder. The classic version of an aperiodic antenna with a load resistor is known to many, here the Bazooka antenna plays the role of a broadband vibrator, and its bandwidth, as in the classical versions, has a large overlap towards higher frequencies.

The antenna diagram is shown in Fig. 27, and the power of the resistor is about 30% of the power supplied to the antenna. If the antenna is used only as a receiving antenna, the power of the 0.125W resistor is sufficient. It should be noted that the "Tesla spiral" antenna, installed horizontally, has an eight-fold directional pattern and is capable of spatial selection of radio signals. When installed vertically, it has a circular radiation pattern.

4. Magnetic antennas.

The second, no less popular type of antenna is an inductive radiator with shortened dimensions, this is a magnetic frame. The magnetic frame was discovered in 1916 by K. Brown and was used until 1942 as a reception area in radio receivers and direction finders. This is also an open oscillatory circuit with a frame perimeter of less than 0.25 wavelength, it is called “magnetic loop”, and its abbreviated name has acquired an abbreviation - ML. The active element of the magnetic loop is inductance. In 1942, an amateur radio operator using the radio call sign W9LZX first used such an antenna at the HCJB mission broadcast station in the mountains of Ecuador. Thanks to this, the magnetic antenna immediately conquered the amateur radio world and has since been widely used in amateur and professional communications. Magnetic loop antennas are one of the most interesting types of small-sized antennas that can be conveniently placed both on balconies and on window sills.

It has the form of a loop of a conductor that is connected to a variable capacitor to achieve resonance, where the loop is the radiating inductance of an oscillating LC circuit. The emitter here is only the inductance in the form of a loop. The dimensions of such an antenna are very small, and the frame perimeter is usually 0.03-0.25 λ. The maximum efficiency of the magnetic loop can reach 90% relative to the Hertz dipole, see Fig. 29.a. The capacitance C in this antenna does not participate in the radiation process and has a purely resonant nature, as in any oscillatory circuit, Fig. 29.b ..

Antenna efficiency strongly depends on the active resistance of the antenna web, on its dimensions, on placement in space, but to a greater extent on the materials used for the antenna design. The bandwidth of a loop antenna is usually from units to tens of kilohertz, which is associated with the high quality factor of the formed LC circuit. Therefore, the efficiency of an ML antenna largely depends on its Q-factor, the higher the Q-factor, the higher its efficiency. This antenna is also used as a transmitting antenna. With small dimensions of the frame, the amplitude and phase of the current flowing in the frame are practically constant along the entire perimeter. The maximum radiation intensity corresponds to the plane of the frame. In the perpendicular plane of the frame, the radiation pattern has a sharp minimum, and the overall pattern of the loop antenna has the shape of a "figure eight".

Electric field strength E electromagnetic wave (V / m) at a distance d from transmitting loop antenna, calculated by the formula:

EMF E induced in foster loop antenna, calculated by the formula:

The eight-dimensional radiation pattern of the frame allows you to use its minima of the pattern in order to detune it in space from closely located interference or unwanted radiation in a certain direction in the near zones up to 100 km.

When manufacturing the antenna, it is required to observe the ratio of the diameters of the radiating ring and the communication loop D / d as 5/1. The coupling coil is made of a coaxial cable, is located in the immediate vicinity of the radiating ring on the opposite side from the capacitor, and looks like in Fig. 30.

Since a large current flows in the emitting frame, reaching tens of amperes, the frame in the frequency ranges 1.8-30 MHz is made of a copper tube with a diameter of about 40-20 mm, and the tuning capacitor into resonance should not have rubbing contacts. Its breakdown voltage must be at least 10 kV with a power input of up to 100 W. The diameter of the radiating element depends on the range of frequencies used and is calculated from the wavelength of the high-frequency part of the range, where the perimeter of the frame is P = 0.25λ, counting from the upper frequency.

Perhaps one of the first after W9LZX, German shortwave DP9IV with ML antenna installed on the window, with a transmitter power of only 5 W, in the 14 MHz band I made QSOs with many European countries, and with 50 W power - with other continents. It was this antenna that became the starting point for the experiments of Russian radio amateurs, see Fig. 31.

The desire to create an experimental compact indoor antenna, which can also be safely called an EH antenna, in close cooperation with Alexander Grachev ( UA6AGW), Sergey Tetyukhin (R3PIN) designed the next masterpiece, see Fig. 32.

It is this low-budget design of the room version of the EH-antenna that can please the radio amateur-newcomer or summer resident. The antenna circuit includes both a magnetic emitter L1; L2, and a capacitive one in the form of a telescopic "whisker".

Particular attention in this design (R3PIN) deserves a resonant system for matching the feeder with the antenna Lsv; C1, which once again increases the Q-factor of the entire antenna system and allows you to slightly raise the antenna gain as a whole. As the primary circuit together with the "mustache" as in the design of Yakov Moiseevich, the braid of the cable of the antenna canvas acts here. With the length of these "whiskers" and their position in space, it is easy to achieve resonance and the most effective operation of the antenna as a whole by the current indicator in the frame. And the provision of the antenna with an indicator device allows us to consider this version of the antenna as a completely finished construct. But whatever the design of magnetic antennas, you always want to increase its efficiency.

Dual-loop magnetic antennas in the form of an eight, relatively recently began to appear among radio amateurs, see Fig. 33. Its aperture is twice as large as the classical one. The capacitor C1 can change the resonance of the antenna with frequency overlap by 2-3 times, and the total perimeter of the circumference of the two loops is ≤ 0.5λ. This is comparable to a half-wave antenna, and its small radiation aperture is compensated by an increased Q factor. It is better to coordinate the feeder with such an antenna by means of inductive coupling.

Theoretical digression: The double loop can be considered as a mixed oscillatory system of LL and LC systems. Here, for normal operation, both arms are loaded on the radiation medium synchronously and in phase. If a positive half-wave is fed to the left shoulder, then exactly the same wave is fed to the right shoulder. The EMF of self-induction generated in each arm will, according to Lenz's rule, be opposite to the EMF of induction, but since the EMF of induction of each arm is opposite in direction, the EMF of self-induction will always coincide with the direction of induction of the opposite arm. Then the induction in the L1 coil will be summed up with the self-induction from the L2 coil, and the induction of the L2 coil - with the L1 self-induction. As in the LC circuit, the total radiation power can be several times higher than the input power. Power can be supplied to any of the inductors and in any way.

The double border is shown in Fig. 33.a.

The design of a two-loop antenna, where L1 and L2 are connected to each other in the form of a figure of eight. This is how the two-frame ML was born. Let's call it conditionally ML-8.

The ML-8, in contrast to ML, has its own peculiarity - it can have two resonances, the oscillatory circuit L1; C1 has its own resonant frequency, and L2; C1 has its own. The task of the designer is to achieve the unity of resonances and, accordingly, the maximum efficiency of the antenna, therefore, the dimensions of the loops L1; L2 and their inductances must be the same. In practice, an instrumental error of a couple of centimeters changes one or another inductance, the tuning frequencies of the resonances diverge somewhat, and the antenna receives a certain frequency delta. In addition, the double inclusion of identical antennas expands the bandwidth of the antenna as a whole. Sometimes constructors do it on purpose. In practice, ML-8 is actively used by radio amateurs with radio call signs RV3YE; US0KF; LZ1AQ; K8NDS and others unambiguously asserting that such an antenna works much better than a single-loop antenna, and changing its position in space can be easily controlled by spatial selection. Preliminary calculations show that for the ML-8 for a range of 40 meters, the diameter of each loop at maximum efficiency will be slightly less than 3 meters. It is clear that such an antenna can only be installed outdoors. And we dream of an effective ML-8 antenna for a balcony or even a windowsill. Of course, you can reduce the diameter of each loop to 1 meter and tune the resonance of the antenna with the capacitor C1 to the required frequency, but the efficiency of such an antenna will drop by more than 5 times. You can go the other way, save the calculated inductance of each loop, using not one, but two turns in it, leaving the resonant capacitor with the same rating, respectively, and the quality factor of the antenna as a whole. There is no doubt that the antenna aperture will decrease, but the number of turns "N" will partially offset this loss, according to the formula below:

From the above formula, it can be seen that the number of turns N is one of the multipliers of the numerator and is in the same row, both with the area of ​​the turn-S and with its quality factor-Q.

For example, a radio amateur OK2ER(see Fig. 34) considered it possible to use a 4-turn ML with a diameter of only 0.8 m in the range of 160-40 m.

The author of the antenna reports that at 160 meters the antenna works nominally and is used more for radio surveillance. In the range of 40m. it is enough to use a jumper that halves the working number of turns. Let's pay attention to the materials used - the copper pipe of the loop is taken from water heating, the clips connecting them into a common monolith are used to install water-supply plastic pipes, and a sealed plastic box was purchased at an electrician's store. The matching of the antenna with the feeder is capacitive, and is performed according to any of the presented schemes, see Fig. 35.

In addition to the above, we need to understand that the following antenna elements negatively affect the quality-Q of the antenna as a whole:

From the above formula, we see that the active resistance of the inductance Rk and the capacitance of the oscillatory system CK, standing in the denominator, should be minimal. That is why all MLs are made of copper pipe, as large as possible, but there are cases when the hinge sheet is made of aluminum. The quality factor of such an antenna and its efficiency drops by a factor of 1.1-1.4. With regard to the capacity of the oscillatory system, then everything is more complicated. With a constant loop size L, for example, at a resonant frequency of 14 MHz, the capacitance C will be only 28 pF, and the efficiency = 79%. At a frequency of 7 MHz, efficiency = 25%. Whereas at a frequency of 3.5 MHz with a capacitance of 610 pF, its efficiency = 3%. Therefore, ML is used most often for two ranges, and the third (lowest) is considered an overview. Therefore, it is necessary to make calculations based on the highest range with a minimum capacity C1.

Double magnetic antenna for a range of 20m.

The parameters of each loop will be as follows: If the diameter of the web (copper pipe) is 22mm, the diameter of the double loop is 0.7m, the distance between the turns is 0.21m, the inductance of the loop will be 4.01μH. The required design parameters of the antenna for other frequencies are summarized in Table 3.

Table 3.

Tuning frequency (MHz)	Capacitance C1 (pF)	Bandwidth (kHz)

In height, such an antenna will be only 1.50-1.60 m. That is quite acceptable for an antenna of the type - ML-8 balcony version and even an antenna hung outside the window of a residential multi-storey building. And its wiring diagram will look like in fig. 36.a.

Antenna power can be capacitively coupled or inductively coupled. Capacitive communication options shown in Fig. 35 can be selected at the request of the radio amateur.

The most budgetary option is inductive coupling, but its diameter will be different.

Calculation of the diameter (d) of the ML-8 tie loop is made from the calculated diameter of two loops.

The circumference of the two loops after recalculation is 4.4 * 2 = 8.8 meters.

Let's calculate the imaginary diameter of two loops D = 8.8m / 3.14 = 2.8 meters.

Let's calculate the diameter of the connection loop - d = D / 5. = 2.8 / 5 = 0.56 meters.

Since in this design we use a two-turn system, the communication loop must also have two loops. We twist it in half and we get a two-turn communication loop with a diameter of about 28 cm. The selection of communication with the antenna is carried out at the time of the SWR specification in the priority frequency range. The coupling loop can be galvanically coupled to the zero voltage point (Fig. 36.a.) and be located closer to it.

Electric emitter, this is another additional element of radiation. If the magnetic antenna emits an electromagnetic wave with the priority of the magnetic field, then the electric emitter will perform the function of an additional emitter of the electric field-E. In fact, it should replace the initial capacitance C1, and the drain current, which previously was uselessly passed between the closed plates of the capacitor C1, now operates on additional radiation. In this case, a fraction of the supplied power will be additionally emitted by electric emitters, Fig. 36.b. The bandwidth will increase to the limits of the amateur radio band as in the EH antennas. The capacity of such emitters is low (12-16pF, no more than 20), and therefore their efficiency in low-frequency ranges will be low. You can familiarize yourself with the operation of the EH antennas by following the links:

For tuning into resonance of a magnetic antenna, it is best to use vacuum capacitors with high breakdown voltage and high quality factor. Moreover, using a gearbox and an electric drive, the antenna can be tuned remotely.

We are designing a budget balcony antenna that you can approach at any time, change its position in space, rebuild or switch to a different frequency. If at points "a" and "b" (see Fig. 36.a.) Instead of a scarce and expensive variable capacitor with large gaps, you connect a capacitor made of sections of RG-213 cable with a linear capacity of 100 pF / m, then you can instantly change the frequency settings, and adjust the tuning resonance with the tuning capacitor C1. The "condenser cable" can be rolled up and sealed in any of the ways. Such a set of capacities can be had for each range separately, and can be connected to the circuit using a conventional electrical outlet (points a and b) paired with an electrical plug. Approximate capacities C1 by ranges are shown in table 1.

Antenna tuning indication in resonance it is better to do it directly on the antenna itself (this is clearer). To do this, it is enough not far from the communication coil on the L1 web (point of zero voltage) to wind tightly 25-30 turns of MGTF wire, and seal the setting indicator with all its elements from precipitation. The simplest diagram is shown in Fig. 37. The maximum readings of the device P will indicate a successful antenna tuning.

To the detriment of the antenna efficiency As the material of the loops L1; L2, you can use cheaper materials, for example, a PVC pipe with an aluminum layer inside for laying a water pipe with a diameter of 10-12 mm.

DDRR antenna

Despite the fact that the efficiency of the classical DDRR antenna is 2.5 dB inferior to the quarter-wave vibrator, its geometry turned out to be so attractive that DDRR was patented by Nortrop and put into mass production.

As in the case of the Groundplane, the main factor in the decent efficiency of the DDRR antenna is a solid counterweight. It is a flat metal disc with high surface conductivity. Its diameter must be at least 25% larger than the diameter of the ring conductor. The elevation angle of the main beam is the smaller, the higher the ratio of the diameters of the counterweight disk, and increases if as many radial counterweights as possible with a length of 0.25λ are fixed around the disk circumference, ensuring their reliable contact with the counterweight disk.

The DDRR antenna considered here (Fig. 38) uses two identical rings (hence the name "two-ring-circular"). At the bottom, instead of a metal surface, a closed ring with dimensions like the top one is used. All grounding points are connected to it according to the classical scheme. Despite a slight decrease in the efficiency of the antenna, this design is very attractive for placing it on the balcony, in addition, with such a solution, it is of interest to connoisseurs of the 40-meter range. Using square constructs instead of rings, the antenna on the balcony resembles a clothes dryer and does not cause unnecessary questions from neighbors.

All its sizes and capacitor ratings are presented in Table 4. In a budget option, an expensive vacuum capacitor can be replaced with feeder sections in a range, and fine tuning is done with a 1-15pF trimmer with an air dielectric, remembering that the linear capacity of the RG213 cable = (97pF / m).

Table 4.

Amateur bands, (m)
Frame perimeter (m)

Practical experience of using the DDRR double ring antenna was described by DJ2RE. The tested antenna of the 10-meter range was made of a copper tube with an outer diameter of 7 mm. To fine tune the antenna, two 60x60 mm copper swivel plates were used between the upper "hot" end of the conductor and the lower ring.

The comparison antenna was a rotary three-element Yagi located 12 m from the ground. The DDRR antenna was located at a height of 9 m. Its lower ring was grounded only through the shield of the coaxial cable. During the test reception, the quality of the DDRR antenna, as a circular radiator, immediately manifested itself. According to the author of the tests, the received signal was two points lower on the S-meter of the Yagi signal with a gain of about 8 dB. When transmitting with a power of up to 150 W, 125 communication sessions were performed.

Note: According to the author of the tests, it turns out that the DDRR antenna at the time of testing had a gain of about 6 dB. This phenomenon is often misleading because of the proximity of different antennas of the same range, and the properties of EME re-emission by them loses the purity of the experiment.

5. Capacitive antennas.

Before starting this topic, I want to remember the story. In the 60s of the 19th century, while formulating a system of equations for describing electromagnetic phenomena, J.C. Maxwell was faced with the fact that the equation for a direct current magnetic field and the equation of conservation of electric charges of alternating fields (the equation of continuity) are incompatible. To eliminate the contradiction, Maxwell, having no experimental data for that, postulated that the magnetic field is generated not only by the movement of charges, but also by a change in the electric field, just as an electric field is generated not only by charges, but also by a change in the magnetic field. The quantity where is the electric induction, which he added to the conduction current density, Maxwell called bias current... Electromagnetic induction has a magnetoelectric analogue, and the field equations have acquired remarkable symmetry. So, one of the most fundamental laws of nature was speculatively discovered, the consequence of which is the existence of electromagnetic waves. Subsequently, G. Hertz, relying on this theory, proved that the electromagnetic field emitted by an electric vibrator is equal to the field emitted by a capacitive emitter!

If so, let us make sure once again what happens when a closed oscillatory circuit turns into an open one and how can the electric field E be detected? To do this, next to the oscillating circuit, we place an electric field indicator, this is a vibrator, in the rupture of which an incandescent lamp is included, it is not yet lit, see Fig. 39.a. We gradually open the circuit, and we observe that the lamp of the indicator of the electric field lights up, Fig. 39.b. The electric field is no longer concentrated between the plates of the capacitor, its lines of force go from one plate to another through the open space. Thus, we have experimental confirmation of JK Maxwell's assertion that a capacitive emitter generates an electromagnetic wave. In this experiment, a strong high-frequency electric field is formed around the plates, a change in which over time induces eddy displacement currents in the surrounding space (Eichenwald A.A. Electricity, fifth ed., M.-L .: State Publishing House, 1928, Maxwell's first equation), forming a high-frequency electromagnetic field!

Nikola Tesla drew attention to this fact that with the help of very small emitters in the HF range, it is possible to create a sufficiently effective device for emitting an electromagnetic wave. This is how Tesla's resonant transformer was born.

* The design of the EH antenna by T. Hard and the transformer (dipole) by N. Tesla.

Is it worth arguing once again that the EH antenna designed by T. Hard (W5QJR), see Fig. 40, is a copy of the original Tesla antenna, see Fig. 1. Antennas differ only in size, where Nikola Tesla used frequencies in kilohertz, and T. Hard created a design for operation in the HF range.

The same resonant circuit, the same capacitive radiator with an inductor and a coupling coil. The Ted Hard antenna is the closest analogue of the Nikola Tesla antenna and was patented as, "Coaxial inductor and dipole EH antenna" (US Patent US 6956535 B2 dated October 18, 2005) for operation in the HF range.

The Ted Hard HF capacitive antenna is inductively coupled to the feeder, although a number of capacitive antennas with capacitive, direct and transformer coupled have long existed.

The base of the supporting structure of the engineer and radio amateur T. Hard is an inexpensive plastic pipe with good insulating characteristics. Foil in the form of cylinders fits tightly around it, thereby forming antenna radiators with a small capacity. The inductance L1 of the formed serial oscillatory circuit is located behind the emitter aperture. The L2 inductor located in the center of the radiator compensates for the antiphase radiation of the L1 coil. The antenna power connector (from the generator) W1 is located at the bottom, it is convenient for connecting the power feeder going down.

In this design, the antenna is tuned by two elements, L1 and L3. By selecting the turns of the L1 coil, the antenna is tuned to the sequential resonance mode for maximum radiation, where the antenna acquires a capacitive character. The tap from the inductor determines the input impedance of the antenna and whether the radio amateur has a 50 or 75 ohm feeder. By selecting a tap from the L1 coil, you can achieve VSWR = 1.1-1.2. With the inductor L3, compensation is achieved with a capacitive nature, and the antenna takes on an active character, in terms of the input impedance close to VSWR = 1.0-1.1.

Note: Coils L1 and L2 are wound in opposite directions, and coils L1 and L3 are perpendicular to each other to reduce mutual influence.

This antenna design undoubtedly deserves the attention of radio amateurs who have at their disposal only a balcony or loggia.

Meanwhile, developments do not stand in one place and radio amateurs, having appreciated the invention of N. Tesla and the design of Ted Hart, began to offer other options for capacitive antennas.

* Antenna family "Isotron" is a simple example of flat curved capacitive radiators, it is manufactured by the industry for use by its radio amateurs, see Fig. 42. The Isotron antenna has no fundamental difference with the T. Horda antenna. All the same serial oscillatory circuit, all the same capacitive emitters.

Namely, the element of radiation here is a radiating capacitance (Sizl.) In the form of two plates bent at an angle of about 90-100 degrees, the resonance is adjusted by decreasing or increasing the bending angle, i.e. their capacity. According to one version, communication with the antenna is carried out by direct switching on of the feeder and the serial oscillatory circuit, in this case the SWR determines the L / C ratio of the formed circuit. According to another version, which radio amateurs began to use, communication is carried out according to the classical scheme, through the communication coil Lsv. VSWR in this case is adjusted by changing the coupling between the series resonance coil L1 and the coupling coil Lsv. The antenna is operational and to some extent effective, but it has a major drawback, the inductance coil, when placed in the factory version, is located in the center of the capacitive radiator, works in antiphase with it, which reduces the antenna efficiency by about 5-8-dB. It is enough to turn the plane of this coil 90 degrees and the antenna efficiency will increase significantly.

Optimal antenna sizes are summarized in Table 5.

* Multi-band option.

All Isotron antennas are single-band, which causes a number of inconveniences when changing from band to band and placing them. When two (three, four) such antennas are connected in parallel, mounted on a common bus, operating at frequencies f1; f2 and fn, their interaction is excluded due to the high resistance of the serial oscillatory circuit of the antenna, which does not participate in resonance. When two single-resonant antennas are connected in parallel on a common bus, the efficiency (efficiency) and bandwidth of such an antenna will be higher. Using the last version of the in-phase connection of two single-band antennas, you need to remember that the total input impedance of the antennas will be half as much and it is necessary to take appropriate measures by referring to (Table 1). An antenna modification on a common substrate is shown in Fig. 42 (bottom). Needless to say, a choke choke line is an integral part of any mini antenna.

Studying the simplest "Isotron", we came to the conclusion that the gain of this antenna is insufficient due to the placement of a resonant inductor between the radiating plates. As a result, this design was improved by radio amateurs in France, and the inductor was moved outside the working environment of the capacitive emitter, see Fig. 43. The antenna circuit is directly connected to the feeder, which simplifies the design, but still complicates full matching with it.

As can be seen from the presented figures and photos, this antenna is quite simple in design, especially in tuning it to resonance, where it is enough to slightly change the distance between the radiators. If the plates are interchanged, the upper one is made "hot" and the lower one is connected to the feeder braid, a common bus for a number of other antennas of the same type can be made, then you can get a multiband antenna system, or a number of identical antennas connected in phase, capable of increasing the overall gain.

Radio amateur with radio call sign F1RFM, kindly provided for general review his antenna design with calculations for 4 radio amateur bands, the diagram of which is shown in Fig. 44.

* Antenna "Biplane"

The Biplane antenna is named for its similarity to the placement of the twin wings of early 20th century aircraft based on the Biplane design, and its invention belongs to a group of radio amateurs (Fig. 45). Antenna "Biplane" consists of two sequential oscillatory circuits L1; C1 and L2; C2, connected in anti-parallel. Emitter power supply, symmetrical with direct coupling. The planes of capacitors C1 and C2 are used as emitting elements. Each emitter is made of two duralumin plates and is located on both sides of the inductance coils.

To eliminate mutual influence, inductors are wound oppositely or are located perpendicular to each other. The area of ​​each plate, according to the authors, will be 64.5 cm for the range of 20 meters, 129 cm for 40 meters, 258 cm for 80 meters, and 516 cm for the 160 meter range, respectively.

The adjustment is carried out in two stages and can be carried out by elements C1 and C2 by changing the distance between the plates. The minimum VSWR is achieved by changing the capacitances C1 and C2 by tuning the transmitter to the frequency. The antenna is very difficult to adjust and requires a complex construction of sealing against the influence of external precipitation. It has no development prospects and is unprofitable.

On the topic of capacitive antennas, it is worth noting that they have occupied a special niche among radio amateurs who do not have the opportunity to install full-fledged antennas, which only have a balcony or loggia at their disposal. Radio amateurs, who have the opportunity to install a low mast on a small antenna field, also use such antennas. All shortened antennas are collectively referred to as QRP antennas. In addition, radio amateurs have a number of errors in the installation and operation of shortened antennas, this is the absence of a locking "feeder choke" or a very close location of the latter on a ferrite base to the shortened antenna web. In the first case, the antenna feeder begins to radiate, and in the second, the ferrite of such a choke is a "black hole" and reduces its efficiency.

* EH antenna of the USSR CA troops in the 40s - 50s of the last century.

The antenna was welded from duralumin pipes with a diameter of 10 and 20 mm. A flat, broadband symmetric split dipole about 2 meters long and 0.75 m wide. Operating frequency range 2-12MHz. Why not a balcony antenna? It was mounted on the roof of a mobile radio room in a horizontal position at a height of about 1m.

The author of this article, back in the 90s, reproduced this design on the balcony of the second floor, and the emitters were made under a clothes dryer on wooden blocks outside the balcony. Copper insulated wires were stretched instead of ropes, see Fig. 46.a. The antenna was tuned using an oscillatory circuit L1C1, a capacitor C2 for coupling with an antenna and a coupling coil Lw. with transceiver, see Fig. 46.b. All air-insulated capacitors with a capacity of 2 * 12-495pF were used from tube radios of the 60s.

Inductor L1 diameter 50 mm; 20 turns; wire 1.2 mm; pitch 3.5 mm. On top of this coil, a plastic pipe (50mm) sawn along the length was tightly put on. A communication coil Lsv was wound on top of it. - 5 turns with taps from 3; 4 and 5 turns, wire 2.2 mm. For all capacitors, only stator contacts were used, and the axes (rotors) on capacitors C2 and C3 were connected by an insulating bridge for synchronization of rotation. A two-wire line should be no more than 2.0-2.5 meters, this is just the distance from the antenna (dryer) to the matching device on the windowsill. The antenna was built in the range of 1.8-14.5 MHz, but when the resonant circuit was changed to other parameters, such an antenna could work up to 30 MHz. In the original, in series with the transmission line in such a design, current indicators were provided, which were adjusted according to the maximum readings, but in a simplified version between the two wires of the two-wire line, a fluorescent lamp hung perpendicular to it, which, at the minimum output power, shone only in the middle, and at maximum power ( at resonance) the glow reached the edges of the lamp. The coordination with the radio station was carried out with the P1 switch and was monitored by the SWR meter. The bandwidth of such an antenna was more than sufficient to operate on each of the amateur bands. With a power input of 40-50W. The antenna did not interfere with television to the neighbors. Other things now, when everyone has switched to digital and cable television, you can supply up to 100W.

This type of antenna refers to capacitive and differs from EH antennas only in the circuit for switching on the emitters. It differs in their shape and size, but at the same time, it has the ability to rebuild in the HF range and be used for its intended purpose - drying clothes ...

* Combination of E-emitter and H-emitter.

Using a capacitive emitter outside the balcony (loggia), this construct can be combined with a magnetic antenna, as Alexander Vasilievich Grachev did ( UA6AGW), combining the magnetic frame with a half-wave shortened dipole. In the radio amateur world, it is well known and practiced by the author at his summer cottage. The electrical circuit of the antenna is quite simple and is shown in Fig. 47.

Capacitor C1 is a trimmer within the range, and the required range can be set by connecting an additional capacitor to the contacts K1. The matching of the antenna and the feeder is subject to the same laws, i.e. loop at the point of zero voltage, see Fig. 30. Fig. 31. This modification has the advantage that its installation can be made really invisible to prying eyes and, moreover, it will work quite effectively in two or three amateur frequency ranges.

A shortened spiral-shaped dipole on a plastic base fits perfectly inside the loggia with wooden frames, but the owner of this antenna did not dare to expose it outside the loggia. I do not think that the owner of this apartment is delighted with this beauty.

Balcony antenna - 14/21/28 MHz dipole fits well outside the balcony. She is inconspicuous and does not attract attention to herself. You can build such an antenna by following the link

Afterword:

In conclusion of the material on the balcony HF antennas, I would like to say to those who do not have and do not expect access to the roof of their house - it is better to have a bad antenna than none at all. Everyone can work with a three-element Uda-Yagi antenna or a double square, but not everyone can choose the best option, develop and build a balcony antenna, work on the air at the same level. Do not change your hobby, it will always come in handy for resting your soul and training your brain, during your vacation or in retirement. Communication over the air gives much more benefit than communication over the Internet. Men who do not have a hobby of their own, have no purpose in life, live less.

73! Sushko S.A. (ex. UA9LBG)

The HF band contains a number of radio frequencies (27 MHz, commonly used by drivers), broadcasting by many stations. There are no TV programs here. Today we will take a look at the amateur series employed by various radio enthusiasts. Frequencies 3.7; 7; 14; 21, 28 MHz of the HF range, related as 1: 2: 4: 6: 8. It is important, as we will see later, it becomes possible to make an antenna that would catch all the ratings (the question of matching is the tenth thing). We believe there will always be people using the information, catch radio broadcasts. Today's topic is a do-it-yourself HF antenna.

We will disappoint many, today we will again talk about vibrators. Objects of the Universe are formed by vibrations (the views of Nikola Tesla). Life attracts life, it is movement. To give life to a wave, vibrations are necessary. Changes in the electric field generate a magnetic response, thus crystallizing the frequency that carries information to the ether. The immobilized field is dead. A permanent magnet will not generate a wave. Figuratively speaking, electricity is a masculine principle, it exists only in motion. Magnetism is more of a feminine quality. However, the authors delved into philosophy.

It is considered preferable to use horizontal polarization for transmission. Firstly, the azimuth pattern is not circular (they casually said), there will certainly be less interference. We know that various objects are equipped for communication, such as ships, cars, tanks. You can't lose commands, orders, words. The object will turn in the wrong direction, and the polarization is horizontal? Disagree with well-known, respected authors who write: vertical polarization is chosen by the connection for an antenna of a simpler design. Talk about the case of amateurs, it's more about the continuity of the heritage of previous generations.

We add: with horizontal polarization, the parameters of the Earth have less influence on wave propagation, in addition, with a vertical front, the front suffers attenuation, the lobe rises to 5 - 15 degrees, it is undesirable when transmitting over long distances. For antennas (unbalanced) with vertical polarization, good grounding is important. The efficiency of the antenna directly depends. It is better to bury the wires with a length of about a quarter of a wave with earth, the more, the higher the efficiency. Example:

• 2 wires - 12%;
• 15 wires - 46%;
• 60 wires - 64%;
• ∞ wires - 100%.

An increase in the number of wires reduces the characteristic impedance, approaching the ideal (of the indicated type of vibrator) - 37 ohms. Note that the quality should not be brought closer to the ideal, 50 Ohm does not need to be coordinated with the cable (in connection, RK - 50 is used). Great thing. Let's supplement the package of information with a simple fact, with horizontal polarization, the signal is added to the reflected Earth, giving an increase of 6 dB. So many disadvantages are shown by vertical polarization, they are used (it turned out interestingly with ground wires), they put up with it.

The device of HF antennas is reduced to a simple quarter-wave, half-wave vibrator. The latter are smaller in size, accept worse, the latter are easier to agree on. The masts are placed vertically, using spacers, stretch marks. Described a structure hung on a tree. Not everyone knows: there should be no interference at half a wavelength from the antenna. Applies to iron, reinforced concrete structures. Wait a moment to rejoice, at a frequency of 3.7 MHz the distance is ... 40 meters. The antenna reaches the eighth floor in height. Making a quarter-wave vibrator is not easy.

It is convenient to erect a tower to listen to the radio, we decided to recall the old way of catching long waves. Internal ferromagnetic antennas are found in Soviet-era receivers. Let's see if the designs are suitable for their intended purpose (catching broadcasting).

HF magnetic antenna

Let's say there is a need to accept frequencies from 3.7 to 7 MHz. Let's see if it is possible to design a magnetic antenna. Formed by a core of round, square, rectangular cross-section. The sizes are recalculated by the formula:

do = 2 √ pc / π;

do is the diameter of the round bar; h, c - height, width of the rectangular section.

Winding is not carried out for the entire length, in fact, you need to calculate how much to wind, choose the type of wire. Let's take an example of an old design textbook and try to calculate a HF antenna of frequencies from 3.7 to 7 MHz. Let us take the resistance of the input stage of the receiver 1000 Ohm (in practice, readers measure the input resistance of the receiver on their own), the parameter of the equivalent attenuation of the input circuit, at which the specified selectivity is achieved, der equal to 0.04.

The antenna we are designing is part of the resonant circuit. It turns out a cascade, endowed with a certain selectivity. How to solder, think for yourself, just follow the formulas. Carrying out the calculation will need to find the maximum, minimum capacity of the trimmer capacitor, using the formula: Cmax = K 2 Cmin + Co (K 2 - 1).

K is the coefficient of the sub-band, determined by the ratio of the maximum resonant frequency to the minimum. In our case, 7 / 3.7 = 1.9. Chosen from incomprehensible (according to the textbook) considerations, for example, given in the text, take equal to 30 pF. Let's not make a big mistake. Let Cmin = 10 pF, we find the upper limit of the adjustment:

Cmax = 3.58 x 10 + 30 (3.58 - 1) = 35.8 + 77.4 = 110 pF.

Rounded, of course, you can take a variable capacitor of a larger range. An example gives 10-365 pF. We calculate the required inductance of the circuit using the formula:

L = 2.53 x 10 4 (K 2 - 1) / (110 - 10) 7 2 = 13.47 μH.

The meaning of the formula is clear, let's add 7 - the upper limit of the range, expressed in MHz. Selecting the coil core. At the frequencies of the range at the core, the magnetic permeability is M = 100, we select the ferrite grade 100NN. We take a standard core 80 mm long and 8 mm in diameter. The ratio l / d = 80/8 = 10. From the reference books, we extract the effective value of the magnetic permeability md. It turns out 41.

We find the winding diameter D = 1.1 d = 8.8, the number of winding turns is determined by the formula:

W = √ (L / L1) D md mL pL qL;

we read the coefficients of the formula visually, using the graphs below. The figures will show the reference numbers used above. Look for the ferrite grade, man does not live by bread alone. D is expressed in centimeters. The authors received: L1 = 0.001, mL = 0.38, pL = 0.9. qL is calculated using the formula:

qL = (d / D) 2 = (8 / 8.8) 2 = 0.826.

We substitute the numbers in the final expression for calculating the number of turns of the ferrite HF antenna, it turns out:

W = √ (13.47 / 0.001) x 0.88 x 41 x 0.38 x 0.9 x 0.826 = 373 turns.

The cascade must be connected to the first amplifier of the receiver, bypassing the input circuit. Let's say more, now we have calculated the means of selectivity in the 3.7-7 MHz range. In addition to the antenna, it turns on the input circuit of the receiver at the same time. Therefore, it will be necessary to calculate the inductance of communication with the amplifier, fulfilling the conditions for ensuring selectivity (we take typical values).

Lw = (der - d) Rin / 2 π fmin K 2 = (0.04 - 0.01) 1000/2 x 3.14 x 3.7 x 3.61 = 0.35 μH.

The transformation ratio will be m = √ 0.35 / 13.47 = 0.16. We find the number of turns of the communication coil: 373 x 0.16 = 60 turns. We wind the antenna with a PEV-1 wire with a diameter of 0.1 mm, we wind the coil with a PELSHO with a diameter of 0.12 mm.

Many people are probably interested in several questions. For example, the purpose of Co is the formulas for calculating a variable capacitor. The author shyly avoids the question, supposedly the initial capacity of the circuit. Hardworking readers will calculate the resonant frequencies of a parallel circuit in which an initial capacitance of 30 pF is soldered. We make a slight mistake by recommending placing a 30 pF trimmer next to the variable capacitor. The chain is being fine-tuned. Beginners are interested in the electrical circuit, which will include a homemade HF antenna ... The parallel circuit, the signal from which is removed by the transformer, is formed by wound coils. The core is common.

An independent HF antenna is ready. You will find this in a tourist receiver (models with a dynamo are popular today). Antennas in the HF range (and even more so in the CB) would be great if the structure was made in the form of a typical vibrator. Such designs are not used in portable equipment. The simplest HF antennas take up a lot of space. The welcome is better. The purpose of the HF antenna is to improve the signal quality. In the apartment, loggia. We told how to make a miniature HF antenna. Use vibrators in the country, in the field, in the forest, in an open area. Material provided by the design guide. The book is full of mistakes, and the result seems to be bearable.

Even old textbooks are guilty of typos missed by editors. It concerns more than one branch of radio electronics.

Did you mean this:

We can say that the 80-meter range is one of the most popular. However, many plots of land are too small for a full-size antenna to be installed in this range, which is what the American shortwave Joe Everhart, N2CX faced. Trying to choose the optimal type of small antenna, he analyzed many options. At the same time, they did not forget the classic wire antennas, which work quite efficiently with a length of more than L / 4. Unfortunately, these end-powered antennas need a good grounding system. Of course, high-quality grounding is not required in the case of a half-wave antenna, but its length turns out to be the same as that of a full-size dipole, powered at the center.

It is no exaggeration to say that the 80-meter range is one of the most popular. However, many plots of land are too small for a full-size antenna to be installed in this range, which is what the American shortwave Joe Everhart, N2CX faced. Trying to choose the optimal type of small antenna, he analyzed many options. At the same time, they did not forget the classic wire antennas, which work quite efficiently with a length of more than L / 4. Unfortunately, these end-powered antennas need a good grounding system. Of course, high-quality grounding is not required in the case of a half-wave antenna, but its length turns out to be the same as that of a full-size dipole, powered at the center.

So Joe decided that the simplest antenna with good performance was the horizontal dipole driven in the center. Unfortunately, as already indicated, the length of the 80-meter half-wave dipole is often an obstacle in its installation. However, the length can be reduced to about L / 4 without fatal performance degradation. And if you raise the center of the dipole and bring the ends of the vibrators closer to the ground, we get the classic Inverted V design, which will additionally save space during installation. Therefore, the proposed design can be considered as an Inverted V on the 40m band, which is used on 80m (see the figure above). The antenna web is formed by two vibrators 10.36 m each, symmetrically descending from the feed point at an angle of 90 ° to each other. During installation, the lower ends of the vibrators should be at least 2 m above the ground, for which the suspension height of the central part should be at least 9 m. The low suspension height provides effective radiation at large angles, which is ideal for communications at distances of up to 250 km. The most important advantage of such a structure is the fact that its projection does not exceed 15.5 m.
As you know, the advantage of a center-fed half-wave dipole is a good match with a 50 or 75-ohm coaxial cable without the use of special matching devices. The described antenna in the range of 80 m has a length of L / 4 and, therefore, is not resonant. The active component of the input impedance is small, and the reactive component is large. This means that when such an antenna is paired with a coaxial cable, the VSWR will be too high, and the level of loss will be significant. The problem is solved simply - it is necessary to use a line with low losses and use an antenna tuner to match it with 50-ohm equipment. A 300-ohm TV flat ribbon cable was used as an antenna feeder. Less losses are provided by a two-wire overhead line, but it is more difficult to bring it indoors. In addition, it may be necessary to adjust the length of the feeder to get within the tuning range of the antenna tuner.
In the original design, the end and central insulators were made of 1.6 mm thick fiberglass scraps, and an insulated mounting wire with a diameter of 0.8 mm was used for the antenna web. Small diameter wires have been used successfully on N2CX radios for several years. Of course, more durable mounting wires with a diameter of 1.6 ... 2.1 mm will last much longer.
The conductors of a flat-panel TV cable are not strong enough and usually break off at the points of connection to the antenna tuner, therefore the necessary mechanical strength and ease of connecting the line to the tuner is provided by an adapter made of foil-clad fiberglass.
The tuner circuit is very simple, and is a series resonant circuit that matches the coaxial cable.
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Here's another option:

Short vertical for a range of 80m

At the end of 2009, Valdek, SP7GXP, designed a shortened vertical antenna for 80 m. The design consists of a vertical whip radiator mounted on a support insulator and at the top separated by a second insulator. A delta-shaped frame is connected to the emitter, and a half-wave dipole is located below the support insulator as a counterweight.

The dimensions of the listed elements of the antenna structure are:
- the length of the radiator from the support insulator to the upper insulator - 8 m;
- length of the radiator installed on the upper insulator - 3 m;
- frame length for fp = 3.8 MHz - about 7.7 m (for fp = 3.5 MHz - about 9.35 m);
- the length of one arm of the dipole (counterweight) for fp = 3.8 MHz - minimum 18.7 m (for fp = 3.5 MHz - minimum 20.35 m);
- the height of the dipole above the ground (roof) surface is at least 2 m.
The frame should be set aside from the vertical radiator. In addition, it serves as two braces for the upper part of the radiator. The length of the RG-58U coaxial cable is at least 26.5 m.
Steps for tuning an antenna using a transceiver and a SWR meter:
- we install the emitter with a frame;
- we stretch the half-wave dipole at a height of at least 2 meters above the surface, but do not connect it to the antenna base;
- connect the supply cable to a half-wave dipole;
- turn on the transceiver in the carrier transmission mode and select the dipole length so as to obtain a minimum SWR at a frequency of 3.780 MHz (or another preferred frequency);
- disconnect the supply cable from the dipole, connect the ends of the dipole, as well as the shield (braid) of the supply cable at one point, below the base insulator (to the roof, ground, etc.);
- we connect the cable core to the emitter;
- turn the transceiver back into transmission mode and, choosing the length of the frame, tune the antenna system to the required frequency (for example, 3.780 MHz).
In order for the antenna to cover the entire range (CW and SSB sections from 3.5 to 3.8 MHz), 3 coils with switches can be used to obtain the corresponding resonant frequencies of the antenna. The coils are installed at the support insulator and the arms of the dipole (counterweight) are connected to two of them, and the vertical radiator is connected to the third. The number of turns of the coil is selected experimentally - depending on the section of the range.
When installing the antenna, the following rules should be followed. If the roof or surface on which the antenna is installed does not allow stretching the full-size dipole in a straight line, you can try to bend its ends ("twist"), be sure to adhere to the requirement to comply with the required installation height (at least 2 m).
To comply with the rules for the safe operation of the antenna, the ends of the dipole ending in insulators should be removed from metal objects (for example, fences, metal walls, etc.). You can not use any "earthen" counterweights or lying on the ground! When installing the antenna on the ground, the lower part, below the supporting insulator, must be in contact with the ground, and when installing on the roof, this part of the antenna (below the insulator) must be connected to the lightning rod.

The frequency range 1-30 MHz is traditionally called shortwave. On short waves, you can receive radio stations located thousands of kilometers away.

Which antenna to choose for shortwave reception

No matter which antenna you choose, it is best that it be external(outdoors), highest located and away from power lines and metal roofs (to reduce interference).

Why is the external one better than the room one? In a modern apartment and apartment building, there are many sources of electromagnetic fields, which are such a strong source of interference that often the receiver only picks up the interference. Naturally, the outside (even on the balcony) will be less susceptible to these interferences. In addition, reinforced concrete buildings shield radio waves, and therefore the useful signal inside the room will be weaker.

Is always use a coaxial cable for the antenna to communicate with the receiver, this will also reduce the level of interference.

Receiving antenna type

In fact, on the HF band, the type of receiving antenna is not so critical. Usually, a wire 10-30 meters long is enough, and a coaxial cable can be connected at any convenient place on the antenna, although to ensure greater broadband (multi-band), it is better to connect the cable closer to the middle of the wire (you will get a T-antenna with a shielded drop). In this case, the braid of the coaxial cable is not connected to the antenna.

Wire antennas

Although more long antennas can receive more signals, they will also receive more interference. This equates them somewhat with short antennas. In addition, long antennas overload (“phantom” signals appear over the entire range, the so-called intermodulation) household and portable radios with strong signals from radio stations. they are small compared to amateur or professional radios. In this case, turn on the attenuator in the radio receiver (set the switch to the LOCAL position).

If you use a long wire and connect to the end of the antenna, it will be better to use a 9: 1 matching transformer (balun) to connect the coaxial cable, because The “long wire” has a high active resistance (about 500 Ohm) and this matching reduces the loss on the reflected signal.

Matching transformer WR LWA-0130, ratio 9: 1

Active antenna

If you do not have the ability to hang an external antenna, then you can use an active antenna. Active antenna- this is, as a rule, a device that combines a loop antenna (or ferrite or telescopic), a broadband low-noise high-frequency amplifier and a preselector (a good active HF antenna costs over 5,000 rubles, although it makes no sense to purchase an expensive one for household radios, something is quite suitable like Degen DE31MS). To reduce interference from the network, it is better to choose an active antenna that runs on batteries.

The point of an active antenna is to suppress interference as much as possible and to amplify the desired signal at the RF (radio frequency) level, without resorting to transformations.

In addition to an active antenna, you can use any indoor antenna that you can make (wire, loop or ferrite). In reinforced concrete houses, the indoor antenna should be located away from the electrical wiring, closer to the window (preferably on the balcony).

Magnetic antenna

Magnetic antennas (loop or ferrite), in one way or another, under favorable circumstances, can reduce the level of "city noise" (or rather, increase the signal-to-noise ratio) due to their directional properties. Moreover, the magnetic antenna does not receive the electrical component of the electromagnetic field, which also reduces the level of interference.

By the way, EXPERIMENT is the basis of radio amateurism. External conditions play an essential role in the propagation of radio waves. What works well for one radio amateur may not work at all for another. The most graphic experiment of radio wave propagation can be carried out with a television decimeter antenna. Rotating it around the vertical axis, you can see that the highest quality image does not always correspond to the direction to the TV center. This is due to the fact that radio waves during propagation are reflected and “mixed with others” (interference occurs) and the most “high-quality” signal comes from the reflected wave, and not from the direct one.

Earthing

Do not forget about grounding(through the heating pipe). Do not ground to the protective conductor (PE) in the socket. Old tube radios are especially "fond" of grounding.

Is a joke

Anti-jamming radio reception

In addition to everything, to combat interference and overloads, you can use preselector(antenna tuner). Using this device can suppress out-of-band interference and strong signals to a certain extent.

Unfortunately, in the city, all these tricks may not give the desired result. When the radio is turned on, only noise is heard (usually, noise is stronger in the low frequency ranges). Sometimes novice radio observers even suspect their radios of malfunctioning or unworthy performance. Checking the receiver is easy. Disconnect the antenna (fold the telescopic antenna or switch to an external antenna, but do not connect it) and read the S-meter. Then extend the telescopic antenna or connect an external one. If the S-meter readings have increased significantly, then everything is in order with the radio receiver, and you are out of luck with the receiving location. If the interference level is close to 9 or higher, normal reception will not be possible.

Finding and eliminating the source of interference

Alas, the city is full of “broadband” interference. Many sources generate broad spectrum electromagnetic waves like a spark discharge. Typical examples: switching power supplies, brushed motors, cars, electric lighting networks, cable TV and Internet networks, Wi-Fi routers, ADSL modems, industrial equipment and much more.

The easiest way to “search” for the source of interference is to survey the room using a pocket radio receiver (no matter what band, LW-MW or HF, just not the FM band). Walking around the room, you can easily notice that in some places the receiver makes more noise - this is the “localization” of the source of interference. Almost everything that is connected to the network (computers, energy-saving lamps, power cables, chargers, etc.), as well as the wiring itself, will “make noise”.

It is in order to somehow reduce the detrimental effect of urban interference that “super-duper” sophisticated radios and transceivers have become popular. An urban radio amateurs simply cannot work comfortably on household equipment, which shows itself worthily “in nature”. Greater selectivity and dynamics are required, and digital signal processing (DSP) can “do wonders” (such as suppressing tonal noise) not available with analog methods.

Of course, the best HF antenna is directional (wave channel, QUARD, traveling wave antennas, etc.). But let's be realistic. It is quite difficult and expensive to build a directional antenna, even a simple one.