Tuning the HF antenna with an antenna analyzer. Antennas and their settings

Each antenna has its own resonant frequency at which it radiates or receives maximum energy. At this frequency, the regimental resistance of the antenna is active and in character. The line supplying energy to the antenna at the resonant frequency must have low losses and must not radiate. This is achieved under the condition that the input impedance of the antenna is equal to the wave impedance of the line, and the latter is equal to the input impedance of the receiver or transmitter.

In practice, the input impedance of an antenna often differs from the impedance of the line. Therefore, to match the antenna with the line, you have to use special matching devices. The more complex the design of the antenna, the more difficult it is to take into account all the factors that affect the input impedance of the antenna, and the antenna tuning must be checked using various devices.

In addition to voltage indicators, radio amateurs use various current indicators. Most indicators are designed for measurements in open lines. The standing wave ratio is determined by the ratio of the voltage (or current) at the antinode to the voltage (or current) at the node.

On fig. 1 shows a schematic diagram of such a bridge. The resistance values ​​R1 and R3 are equal to each other.

If the line is matched correctly and the resistance R3 is equal to the wave impedance of the line, the bridge will be balanced and the high-frequency voltmeter included in the diagonal of the bridge will show zero.

However, if the line is not matched to the load, the voltmeter reading will not be zero. The relationship between standing wave ratio and voltmeter readings is shown in Figure-2.

The transmitting antenna is considered good if the standing wave ratio does not exceed 2. This is explained by the fact that the decrease in power in the load with a change in the value of the load resistance does not occur sharply, and therefore some deviation from the traveling wave mode is permissible.

A schematic diagram of a bridge for measuring the standing wave ratio is shown in fig. 3. A view of the installation of this device is shown in fig. 4 and 5. The resistances R1, R2 and R3, together with the wave impedance of the feeder, form a bridge. The feeder is connected to the “Line” socket. To the coaxial socket "Input" high-frequency voltage is supplied from the generator. The oscillations supplied to the bridge are rectified by a germanium diode. The constant voltage is measured using a voltmeter included in the "+Input" and "-" sockets.

The device is mounted in a case measuring 75x50x45 mm.

Then, a non-inductive resistance of 75 ohms is included in the coaxial socket “Line”. In this case, the voltmeter included in the diagonal of the bridge should show zero at all frequencies.

Figure 6 shows a schematic diagram of a bridge that allows you to directly read the value of the measured wave resistance.

On fig. 7 shows a view of the installation of this device. The bridge is equipped with its own indicator with a sensitivity of 100 µA

As a variable resistance, a resistance of the SP type was used, in which the dill cover was removed. Since usually wave resistances have a value from30 to 300 ohms, in most cases a resistance R3 of 680 ohms can be used. If you need to measure a higher wave resistance, then in series with the variable resistance R3, an additional non-inductive resistance is included.

When measuring at short wavelengths. i.e. up to frequencies of 30 MHz, there is no need to shield the resistance R3. At higher frequencies, the resistance P3 is shielded using a transverse baffle. The axis of resistance is extended with a sleeve made of insulating material.

When constructing the appliance, care must be taken to keep the connecting wires as short as possible and as uniform in length as possible, so that their own capacitances and inductances are minimal and uniform.

S. Khazan. "Radio" N5, 1956

In the manufacture of small-sized radio transmitting devices (portable radio stations, radio microphones, etc.) to obtain maximum efficiency requires tuning of the antenna connected directly to the output of the transmitting path. One of the criteria for tuning the antenna is to obtain the maximum strength of the electromagnetic field in the far zone. To assess the field strength, you can assemble a simple electromagnetic radiation detector, the circuit of which is shown in Fig. 1.

V. Efremov, Essentuki,
For effective work any transmitting radio station needs to minimize the loss of RF energy that is inevitable when it is transmitted from the radio transmitter (TX) to the antenna via the feeder line. This is possible only when high quality agreements and, therefore, in the presence of a device that allows you to control them with sufficient accuracy. In practice, the most widely used are meters built according to either bridge-type circuits or using measuring current transformers or directional couplers of various designs. All of them in certain cases have both advantages and disadvantages, which is quite fully described in the literature [1, 2, 3,4]. Taking this into account, it is desirable to have a fairly universal SWR meter, as well as a load equivalent in its composition (built into the device).

It is these qualities that a universal SWR meter has, the circuit of which is shown in Fig. 1.

A. Titov, Tomsk PA 7/8'2009 Voltage standing wave ratio (VSWR) meters are used to determine the quality of coordination between individual nodes of radio engineering paths. Due to the widespread development of systems cable television it is very important to know its meaning in each case. The proposed device is designed to measure VSWR.

Transmitted power meter and SWR It is known that successful operation on the air largely depends on the efficiency of the antenna of an amateur radio station. There is a wide variety of shortwave antennas. Novice radio amateurs usually use the simplest ones that do not require large expenses. More experienced install multi-element directional antennas on high masts with remote control the position of the main lobe of the radiation pattern. But any antenna will give good results only when properly tuned. The proposed device will provide significant assistance to the radio amateur in tuning the antenna.

Typically, amateur designs use a directional coupler-based SWR meter with an incident and reflected wave switch and a sensitivity control. When setting up the transmitter, it is necessary to perform a large number of manipulations not only with the control elements of the P-circuit, but also with the SWR meter. The device described below makes it possible to simplify the procedure for matching the transmitter and the load.

The device (Fig. 1) allows you to measure the SWR and the power delivered to the load in 50 or 75 Ohm feeders.

L. NIKOLSKY, B. TATARKO, Tver When tuning antennas in amateur radio practice, bridge meters of two types are used: unbalanced and balanced. The former are known as SWR meters and are relatively widespread. The latter are usually called antenoscopes in the literature. They are less common, although they allow you to get some additional (compared to SWR meters) information about the antenna-feeder path of the radio station, the analysis of which can facilitate its tuning.

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1 Building a HF Antenna A manual for beginner radio amateurs Introduction. An antenna is a radio device that converts radio wave energy into an electrical signal and vice versa. Antennas differ in type, purpose, frequency range, radiation pattern, etc. In this article, we will look at building the most common radios. amateur antennas.!!important!! 1. Best Amplifier it's an antenna! Remember this phrase like a multiplication table!! A good, tuned antenna will allow you to listen and communicate with very weak and distant stations. A bad antenna will negate all your efforts to buy or build a receiver / transceiver. 2. The construction of good antennas is associated with work at height (masts, roofs). Therefore, exercise all safety and caution measures. 3. It is strictly forbidden to approach and touch the antenna or drop cables during a thunderstorm!! Now consider the antennas themselves. Let's start with the simplest and go to the highest quality. Antenna "Inclined beam" This is a piece of copper wire, which is fixed at one end to a tree, a lamppost, the roof of a neighboring house, and the other side is connected to the receiver / transceiver. Advantages: - simple design. Disadvantages: - weak amplification, highly susceptible to urban noise, requires coordination with the transceiver / receiver. Manufacturing. Wire type any copper. Single-core, stranded, you can even computer " twisted pair" use. Any thickness, but "so as not to break" from its weight, tension and wind. On average, the cross section sq. mm. Length. If only for the receiver, then any, from 15 to 40m. If for a transceiver, then the length should be approximately L / 2 of the range on which you will work. For example, for a range of 80m = L/2 = 40m. But, always take with a margin of 5-7m.

2 Antenna wire cannot be tied directly. It is necessary to install several insulators at the end of the antenna web. Ideal insulators "nut type": What these insulators are for should be clear from their very name. They isolate the antenna sheet by electricity from the tree, pole and other structures where you will mount the antenna. If nut insulators are not found, you can make homemade ones from any durable dielectric material: - plastic, textolite, plexiglass, pvc tubes, etc. Wood and derivatives (chipboard, fiberboard, etc.) cannot be used. At the ends of the antenna there should be 3-4 insulators, with a distance of 30-50cm from each other. Typical Sloped Beam Antenna Installations

3 The input impedance of the receiver or transceiver is usually standard and equal to 50 ohms. The "Inclined Beam" antenna has a significantly higher resistance, so you can't just connect it to a receiver or transceiver. You need to connect through a matching device. Here is the diagram: It is very easy to match the antenna. 1. Set the switch to the extreme right position so that all turns of the coil are turned on. 2. We twist the capacitors C1 and C2, achieving the loudest possible reception of stations or air noise. 3. If it didn’t work out, switch the button switch further and repeat the setup procedure. When the antenna is matched, you will hear a sharp increase in the volume of stations or air noise. Conclusion. Such an antenna is good for beginner radio amateurs who basically only listen to the air. Yes, it is very noisy, it receives domestic, urban interference, etc. But, as they say, for lack of a better thing, it will do. We also want to warn you. If you have a low power transceiver, 1-5W, then you will be very weakly heard on such an antenna, or you will not be heard at all. Keep this in mind when building or buying a low power transceiver. P.s. Antenna suspension height "Inclined beam". For such an antenna, there is a simple rule: the lower, the worse. And vice versa. If, for example, you pull it over a fence, at a height of 3m, you can only hear local radio amateurs, and that's not a fact. Therefore, raise the antenna as high as possible. The ideal solution between the roofs of multi-storey, high-rise buildings. The real solution is not lower than meters from ground level.

4 Antenna "Dipole" Introduction. We immediately pay attention to the little things, but important)), the stress in the word on the letter I, the dipole. This is already a more serious antenna than an inclined beam. A dipole is two wires in the center of which is connected coaxial cable reduction to the transceiver. The dipole length is L/2. That is, for a section of the 80m range, the length is 40m. Or 20m of wire in each arm of the dipole. For a more accurate calculation, use formulas. 1. Exact formula: Dipole length = 468/F x, where F is the frequency in MHz of the middle of the range for which you are making the dipole. Example for 80m range: - frequency 3.65 MHz. 468/3.65 x = meters. Note this is the total length of the dipole. This means that each shoulder will be 2 times smaller, that is, by a meter. The error in the construction of the dipole arms should be minimized, no more than 2-3 cm. The most important thing is that the shoulders are the same length. 2. There are also online “calculators” on the Internet for calculating dipoles and other antennas: etc. Making a Dipole. For the manufacture of the antenna, we need, in the same way as for the inclined beam, a copper wire. Section 2.5-6 sq. mm. You can use an insulated wire; at low-frequency ranges, PVC insulation introduces insignificant losses. Dipole placement is similar to tilt beam placement. But, here the height of the suspension plays a more prominent role. A low hanging dipole will not work! For normal operation, the height of the dipole suspension must be at least L/4. That is, for the 80m range it should be at least 17-20m. In case you do not have such a height nearby, then the dipole can be made on the mast so that it takes the shape of an inverted V. Here are the drawings on how to hang the dipole correctly:

5 The last option for setting the dipole is called "Inverted-V", that is, the shape of an inverted V. The center of the dipole must be at least L / 4, that is, for 80m band 20m. But, in real conditions, it is allowed to hang the center of the dipole on small masts, trees, 11-17m high. The dipole at such a height will work, however, noticeably worse. The dipole is connected with a coaxial cable, with a wave impedance of 50 ohms. This is either a domestic cable of the PK-50 series, or an imported RG series and similar. The length of the cable does not play a special role, but the longer it is, the greater the attenuation of the signal will be in it. It is the same with the thickness of the cable, the thinner the more signal attenuation. The normal cable thickness for a dipole (measured by the outer diameter) is 7-10mm.

6 Options for connecting the cable to the dipole. At this point, we ask you to be very careful, because now you will learn the many years of experience of the "experienced";). Modern world this is the world of household radio interference - powerful, fat, whistling, chirping, growling, pulsating and other bad ones. The reason for the interference is our modern life: - TVs, computers, LED and energy-saving lamps, microwave ovens, air conditioners, Wi-Fi routers, computer networks, washing machines etc. and so on. This whole set of “life” creates hellish noise on the radio, which sometimes makes it impossible to receive amateur radio stations. Therefore, it is no longer possible to connect a dipole as before, in Soviet times. Now more. 1. Standard cable connection to the dipole. The arms of the dipole are screwed onto any strong, dielectric plate. The central core of the cable is soldered to one shoulder, the cable braid to the second shoulder. You can not screw the cable, only solder. Such a connection was standard in Soviet times, when there was no domestic interference on the air. Now such a connection can be used only in one case: - you live in a country house or in a forest, you have a very high receiver sensitivity and high transmitter power (100W or more). But, this rarely happens, so let's move on to modern connection options.

7 2. Connection option for the city, when using a powerful transceiver transmitter. The very connection of the cable to the dipole is the same, but before soldering we put ferrite rings on the cable, the more the better. The main thing is that these rings should be as close as possible to the place where the cable is soldered, almost very close. Here, according to this principle: It is desirable to use rings with a magnetic permeability of 1000NM. But, any that you find will do, and which will sit tightly on your cable. You can use rings from TVs and monitors: After installing the rings on the cable, put heat shrink tubing on them and press them with a hair dryer so that they fit snugly. If there are no such technologies, then in our way, wrap tightly with electrical tape;). This method will slightly reduce the noise level at the reception. For example, if your noise was at the level of 8 points, then it will become 7. Not much, of course, but better than nothing. The essence of this method is ferrite rings reduce the reception of interference by the cable itself.

8 3. Connection option for the city, as well as for low-power transmitters. The best option. There are two ways to connect. 1. We take a ferrite ring of the required diameter, with a permeability of 1000NM, wrap it with electrical tape (so as not to damage the cable), and thread 6-8 turns of the cable through it. Then solder the cable to the dipole in the usual way. We have a transformer. It must also be connected as close as possible to the soldering points of the dipole. 2. If you don't have a big ferrite ring to run a thick, stiff coax cable through, then you'll have to solder. We take a smaller ring, and wind 7-9 turns of wire on it, with a diameter of 2-4 mm. You need to wind it with two wires at once, and also wrap the ring with electrical tape so as not to damage the wire. How to connect is shown in the figure: That is, we solder the dipole arms to the two upper wires of the transformer, and the central core and cable braid to the two lower ones.

9 This connection of the cable to the dipole kills two birds with one stone: 1. reduces the level of noise received by the cable itself. 2. Matches a balanced dipole, with an unbalanced cable. And this, in turn, increases the chance that you, with a weak transmitter (1-5W), will be heard. Conclusion. The Dipole antenna is a good antenna, already has a small radiation pattern and has better reception and amplification than the Oblique Beam antenna. The dipole, especially with the 3rd connection option, is the ideal solution if you go to the forests and hikes, to work on the air from there. And at the same time you have a low-power transceiver with an output power of 1-5W. Also, the dipole is an ideal solution for the city and for beginner radio amateurs, because. it's easy to stretch between rooftops, doesn't contain any expensive parts, and doesn't need to be tuned if you get it right in the first place. Antenna "Delta" or triangle Introduction. The triangle is the best low-frequency HF antenna that can be built in an urban environment. This antenna is a triangular frame made of copper wire, stretched between the roofs of 3 houses, a drop cable is connected to the break in any corner.

10 The antenna is a closed loop, so household interference is in-phase canceled in it. The noise level of the Delta is several times lower than that of the Dipole. Also, Delta has more gain than a dipole. To work on distant stations (over 2000 km), one of the corners of the antenna must be raised, or vice versa, lowered. That is, so that the plane of the triangle is at an angle to the horizon. Illustrative examples (approximately): Inclined beam noise level 9 points. Dipole with simple connection noise level 8 points. Dipole with transformer connection noise level 6.5 points. Triangle noise level 3-4 points. Here is a video comparing a dipole with a triangle (delta) Have you looked?) Compared?) If you don’t understand what the noise level for reception is, then you can check it right now. Listen to online receivers and compare their noise levels. It is shown here: This is the S-meter scale, which shows the level of the received signal. When there is no signal, it shows the noise level. Remember how radio amateurs say "I hear you 5:9"? 5 is the signal quality, and 9 is the S-meter volume level. Now, listen to the receivers and compare the noise levels: As you can see, on one receiver the noise level is S5, on the second S8. The difference is very audible. And the whole reason is in the antennas. Do you understand now how important it is to make a good and high-quality antenna?

11 Making a triangle. The triangle is made of copper wire. It stretches between the roofs of neighboring houses. If the triangle is strictly horizontal to the ground, then it will radiate upward. With this arrangement, only short-range communications up to 2000 km will be possible. In order for long-distance communications to be possible, it is necessary to rotate the plane of the triangle at an angle to the horizon. The length of the delta wire is calculated by the formula: L (m) = 304.8 / F (MHz) Or you can use the online calculator on the site: For the 80m band, the length of the triangle should be 83.42m, or 27.8m each side. Suspension height not less than 15m. Ideally 25-35m. Connecting the cable to the triangle. You can’t just connect a 50-ohm cable to a triangle, because the impedance of the triangle is Ohm. It must be matched with the cable. For these purposes, matching transformers are created. They are also called balloons. We need a 1:4 balun. It is possible to make a balun qualitatively and correctly only with the help of instruments that measure the parameters of the antenna. Therefore, we will not give a description of its manufacture. For beginner hams, the only option is to either buy a balun or go to more experienced hams in your neighbourhood, such as the local ham radio club, and ask for their help. For a sample, which balun is needed: Conclusion. In conclusion, once again we draw your attention to the fact that the Antenna is the most important element in a radio amateur. The best!! By building a good antenna, you will be heard loudly, even if you have a homemade transceiver with 1-5W output power. And vice versa: - you can buy a Japanese transceiver for 2 thousand American rubles, but the antenna was made bad, as a result, no one will hear you). Therefore, measure 1000 times, and once make a good antenna. Take your time, do not rush, calculate everything, think over and measure. Let's give some advice: if you don't know how far between your houses, look in Yandex-maps, there is a ruler function there + the maps were updated in 2015. You can count the antenna on them.

12 Important points where and how not to put antennas. Some put low-frequency HF antennas on masts, right on the roofs of residential buildings. It is absolutely impossible to do this, and here's why: 1. The dimensions of the antennas are always calculated taking into account the height to the ground. If you put it on the roof, then the height will be considered not from the ground, but from the roof. Therefore, if you have an 18-storey building, and you put the antenna on the roof, consider that you put it at a height of 2-3m from the ground. She will not work for you. 2. A residential building is a hellish swarm of household noise. A roof mounted antenna will catch them all, and even ferrite rings and transformation won't help!! Therefore, if you make wire antennas for low-frequency HF bands (80m, 40m), then: - place them as far as possible from the walls of houses. Hang antennas between rooftops, not over rooftops. - Raise them as high as possible. - always use ferrite rings or matching baluns and transformers. That's all, good luck building a good and low noise antenna! 73!

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TECHNICAL PASSPORT Shortwave amateur radio antenna ZS6BKW 80...10 m

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IN-PHASE ANTENNA ARRIVALS Peskov SN, Director of the MVKPK, Ph.D. April 009 Our group of companies "Polyus-S" carries out calculations of antenna systems for difficult reception conditions for analog and digital (DVB-T)

The operation of various modern means of communication is impossible without such devices for receiving and transmitting radio waves as short-wave antennas (abbreviated as HF antennas). The demand and popularity of these devices are due to the wide variety of their types, as well as the possibility self-manufacturing. They are especially common in amateur radio communications with a permitted broadcast range from 1.81 to 29.7 MHz.

Hertz dipole

The Hertz dipole (half-wave vibrator) is the simplest device of this type, consisting of a vertical support and two arms with a total length of 1/2 of the received or emitted wave. So, at a wavelength of 160 meters, the length of the two arms of the dipole should be 80 meters. When mounting on the roof of a high-rise building, vertical racks are not used, fixing the arms of the dipole on short supports.

Shortened Hertz dipole

Such an antenna kv differs from the previous one in a shorter arm length (up to 1/5 of the length of the received or emitted wave), as well as inductors installed on them and end capacitive loads in the form of metal disks or "asterisks" from wires or wire.

Spiral Antennas

The classic device of this type ("Tesla Spiral") consists of two spirals located on crosses, interconnected by a jumper (traverse).

Antenna Power

Such a device is connected to a transceiver (receiving-transmitting equipment) with a thick coaxial cable with a characteristic impedance of 50-75 ohms.

Antenna Assembly

A small device of this type is assembled by winding two flat spirals with a diameter of 90 cm on a frame made of a polypropylene pipe, consisting of two crosses and a 90-92-cm crossbar (traverse) connecting them. The material for the spirals is a single-core insulated copper wire with a diameter of 1.5 mm.

Transformer

For this device, an air transformer is used with an operating wavelength range of 10 to 100-160 meters. They make it by winding 16 turns of a double wire 1.5 mm thick on a hollow 140 mm frame with a diameter of 25 mm. The length of the wire winding should be 95-100 mm.

Antenna tuning

The setup process includes the following steps:

• Setting the FAC (standing wave ratio) - is performed using a special device or crocodile clips fixed on the vibrator spirals and moved along them, which leads to a change in the position of the power point. The FAC value obtained during the tuning process at the found frequency should be within 1.0-1.2.
• Adjustment of the resonance frequency is carried out by changing the length of the vibrator wires using the same clamps as in the previous paragraph. The adjustment is made by moving the clamps along the insulated wire of the spirals.

Antenna Gain, Bandwidth and Beam Angle

The helical transmitting antenna is placed horizontally at a height equal to 1/8 of the wavelength it radiates.

Magnetic Antennas

The most common HF antenna design is the magnetic-loop (magnetic loop), consisting of:

• Duralumin or copper radiating ring with a diameter of 25-80 cm;
• Communication loops, the diameter of which is 5 times smaller than that of the radiating ring;
• Supply cable (feeder) with a wave impedance of 50 Ohm;
• Powerful resonant frequency tuning capacitor.

They install such simple home-made transmitting devices both on high masts, roofs of high-rise buildings, and on balconies or window sills of apartments. Thanks to a tuning capacitor capable of operating at power up to 100 watts, these shortwave amateur radio antennas operate in the range from 1.8 to 27 MHz.

Capacitive antennas

Multi-band antenna

A multi-band antenna is a device that allows broadcasting in all short wave bands allowed for amateurs. Due to this property, multibands have gained great popularity and distribution.

One of the multi-range typesUA1DZ has the following construction:

• Vibrator 9.3 m long
• 3-meter stand;
• 4-5 guy lines;
• 10-14 additional flexible counterweights-guy lines 9.4 m long.

The connection of such antennas and transmitters is carried out using a 50 ohm coaxial cable.

The main disadvantages that such multi-range structures have are their bulkiness, high windage and the risk of being struck by lightning when installed on the roof of a high-rise building or other multi-storey building.

Vertical Antenna (Ground Plane)

Vertical antennas of the Ground Plane type are devices designed for broadcasting on the bands from 14 to 24-28 MHz. The main components of such vertical square antennas are a 2-meter mast, a duralumin vibrator 2 to 5 meters long, 4-5 counterweights 2.5-3 meters long and a 50-ohm coaxial power cable.

They are installed both on the roofs of skyscrapers and on the gables of private houses.

Short dipole antenna

The simplest device of this type at 7 MHz is a design consisting of the following parts:

• A wire vibrator divided into two 3-meter arms with insulators and braces at the ends. Small pieces of textolite are used as insulators; a strong linen nylon cord is used for braces.
• Two extension 140-turn coils made of copper wire 0.5-0.6 mm thick;
• Central unit with transformer (balun);
• Feeder - 50 ohm coaxial cable.

Such a shortened dipole is used both in stationary and in the field, fixing it at a height of 3 to 4 meters.

On a note. In order to adjust such a device for resonance, it is necessary to uniformly shorten the length of the vibrator arms located horizontally or at an angle. After changing the length of the arm, the guy shortening it is attached to the nearest tree or other stable support.

DIY vertical HF antenna

The most popular for self-manufacturing are short-wave transmitting devices such as vertical antennas.

The simplest and most effective of them is done as follows:

1. A wooden post 2.5-3 meters high is dug into the ground;
2. A junction box is fixed on a dug-in post with self-tapping screws;
3. A high-frequency choke is placed in a fixed box - a coil with turns of an insulated coaxial cable wound around it;
4. A two-wire stranded copper cable with a cross section of 2 mm is connected to the choke output;
5. The wire is threaded through the through-rings of a cheap 6-meter carbon fiber rod;
6. The end of the wire is fixed on the tip of the rod using a conventional plastic clamp-tie;
7. In the middle of the rod, a round platform with wire braces is fixed;
8. 2 clips and one clamp-holder (KTR) for polypropylene pipes with a diameter of 32 mm are attached to the top of the post;
9. With the help of clips and a holder, a rod with an emitter (a wire threaded through the through-rings) is fixed on a pole;
10. With guy wires, the mast with the emitter is leveled and securely fixed. Guys are fixed on stable nearby poles, trees, hooks screwed into the supporting structures of buildings and capital buildings.

The supply wire for kV antennas of this type is used with a wave impedance of 50 ohms.

The maintenance of such a device comes down to periodically checking the integrity of the emitter by testing it with a multimeter, replacing the mast knees broken by the wind, and adjusting the tension of the guys.

Selecting the first HF transceiver

When choosing the first transmitting device (transceiver), novice radio amateurs must consider:

• Dimensions and Weight - The radio should be of such dimensions and weight that it can be easily carried in the hands or in a backpack.
• Functionality - for a beginner radio amateur, a transceiver with a small number of basic settings (resonant frequency, power, SWR) is enough;
• Reliability and warranty - like any other equipment, a shortwave radio must have guarantee period service;
• Possibility of programming equipment using a personal computer.

It is not recommended for novice radio amateurs to purchase expensive and very difficult to operate and maintain shortwave radio stations. It will be very difficult for a beginner interested in amateur radio to understand such equipment; if he loses interest in this business, selling such an expensive radio station for the same amount that it was bought will be very difficult.

Other Antenna Designs

From other designs Antennas kv band attention deserves a vertical helical half-wave vibrator for waves with a length of 80 meters, consisting of:

• 120 cm spiral of insulated copper wire with a diameter of 1-1.5 mm;
• Traverse height 150 cm;
• Counterweight at least 80 cm long;
• matching device;
• High frequency autotransformer;
• Power line from a coaxial cable with a wave impedance of 50 ohms.

Such vertical antennas are used in conditions of limited space in small personal plots, on the roofs of multi-storey buildings and other high-rise buildings.

The simplest homemade antennas

The easiest shortwave devices described above to manufacture are:

• Whip antenna;
• full size dipole.

You can make them yourself from improvised inexpensive materials, without using special tools and equipment.

A few words about shortwaves

Shortwaves are radio amateurs who broadcast in the shortwave range. People involved in the design, manufacture and repair of transmitting devices conduct communication sessions from various parts of the world. At the same time, for each of them, the farthest point from which the radio session was held is considered an achievement.

On a note. According to the current legislation of the Russian Federation, broadcasting is available for shortwave radio amateurs on 10 shortwave bands with the following wavelengths: 2200 m, 160 m, 80 m, 40 m, 30 m, 20 m, 16 m, 15 m, 12 m, 10 m. The use of high frequency bands is prohibited.

Mobile phone antennas

Not so long ago in many models mobile phones directional antennas large enough for these devices were used. However, with the development of telecommunication technologies, the operation of mobile communications has gradually moved from shortwave to HF bands up to 2500 MHz. This operating frequency corresponds to a wavelength of only 12 cm, so that a small transmitter built into the phone is sufficient for efficient communication.

Thus, a properly assembled, installed and tuned shortwave antenna is the key to stable and high-quality communication with radio amateurs living in the most remote corners of the planet. Due to the wide variety of designs and models, such a transmitting device assembled from improvised materials can be installed in almost any accessible place: on the roof, balcony, and even inside the dwelling.

Video

Very often on amateur radio bands you can hear discussions about the advantages and disadvantages of certain antennas. As a boy, I was very upset that I did not understand what was being said. Today, with me personally, of course, the situation is different, but for those boys (or adult radio amateurs) who do not have special knowledge in the field of radio engineering in general and antennas in particular, and for those who have no time to read long articles with formulas, I will try in simple terms talk about antennas so that they can tune the few antennas that a novice radio amateur usually has. So to speak "on the fingers", like Chapai on potatoes :-) Many do not understand the importance of a good coordination of the Radio-Transmission Line-Antenna path. Or rather, they understand the importance, but are completely unable to really assess the state of affairs. Most often, they are satisfied with the readings of the built-in SWR meter close to one. The worst thing about this is that in case of a bad state of affairs, the owner of the radio increases the power until they answer. And how much power will be directed to the neighbor's TV and will go to warm up the atmosphere - the second question ... Let's try to figure it out. The picture schematically shows a diagram of three devices and two transitions between them.

The secret is that the SWR meter shows what it "sees" on the transceiver connector. The rest of the devices and impedances "hide behind the backs" of those in front, like one nested doll inside another. And at every junction and device, there are losses due to attenuation in the cable or transmission line and poor SWR. First, let's define the units of measurement. For specialists, for example in the field of agriculture, the term dbi is closer to the medical term than to the concept of "how many times". Therefore, to begin with, the loss table in dB and the percentage decoding, in which everyone understands well. And now the table of physical losses in lines and junctions, depending on the range calculated special program simulation of transmission lines as well as losses due to poor matching.

Looking at this picture, it is easy to agree that in an unfavorable scenario, nothing can get into the antenna at all :-).

And now closer to radio engineering. If the antenna has a real impedance equal to the resistance of the transmission line, whether it be a coaxial cable, a quarter-wave transformer or a tuned line, then the SWR meter at the transceiver connector will measure the real SWR of the antenna-feeder device (AFD). If not, the SWR meter will show a match with the cable rather than with the entire system. Due to the fact that it is very inconvenient to measure SWR directly on an antenna already raised above the ground, tuned lines and quarter or half-wave cable segments are often used to communicate with the antenna, which are also transformers that accurately “transmit” the SWR value of the antenna to the radio input (impedance). That is why, if the antenna impedance is unknown, or it is only being adjusted, it makes sense to use a coaxial cable of a certain length. How to calculate the cable length for a certain frequency, I already wrote here http://gosh-radist.blogspot.com/p/i.html, and the tables above will help you choose the lesser of two evils - either feeder losses or SWR losses: - ). In any case, what I described above is better to know than to remain in the dark ... When choosing, installing or configuring a particular antenna, you need to know several of their main properties, which can be described by the following concepts:

resonant frequency

Antenna transmits or receives electromagnetic oscillations with the greatest efficiency only when the frequency of the exciting oscillation coincides with the resonant frequency of the antenna. It follows from this that its active element, vibrator or frame has such a physical size that resonance is observed at the desired frequency. By changing the linear dimensions of the active element - the emitter, the antenna is tuned to resonance. As a rule (based on the best efficiency/labor ratio and matching with the transmission line), the length of the antenna is equal to half or a quarter of the wavelength at the center operating frequency. However, due to capacitive and end effects, the electrical length of an antenna is longer than its physical length. The resonant frequency of the antenna is affected by: the proximity of the antenna above the ground or some conductive object. If this is a multi-element antenna, then the resonant frequency of the active element may still change in one direction or another, depending on the distance of the active element in relation to the reflector or director. Antenna handbooks provide graphs or formulas for finding the free space velocity factor of a vibrator as a function of the ratio of wavelength to vibrator diameter. In fact, it is rather difficult to determine the shortening coefficient more accurately, since the height of the antenna suspension, surrounding objects, soil conductivity, etc. have a significant effect. In this regard, in the manufacture of the antenna, additional adjustment elements are used, which make it possible to change the linear dimensions of the elements within a small range. In a word, it is better to “bring” the antenna to working condition at the place of its permanent location. Usually, if the antenna is a wire type dipole or Inverted V, shorten (or lengthen) the wire connected to central core feeder. So smaller changes can achieve a greater effect. Thus, the antenna is tuned to the operating frequency. In addition, by changing the slope of the beams in Inverted V, the SWR is adjusted to a minimum. But even this may not be enough. More on that below.

Impedance or input impedance (or radiation resistance)

The buzzword Impedance refers to the complex (total) resistance of the antenna and it varies along its length. The point of maximum current and minimum voltage corresponds to the lowest impedance and is called the excitation point. The impedance at this point is called the input impedance. The reactive component of the input impedance at the resonant frequency is theoretically zero. At frequencies above resonant, the impedance is inductive, and at frequencies below resonant, it is capacitive. In practice, the reactive component in most cases varies from 0 to +/-100 ohms. Antenna impedance may also depend on other factors, such as proximity to the ground or any conductive surfaces. In the ideal case, a symmetrical half-wave vibrator has a radiation resistance of 73 ohms, and a quarter-wave asymmetric vibrator (read pin) - 35 ohms. In reality, the influence of the Earth or conductive surfaces can change these resistances from 50 to 100 ohms for a half-wave antenna and from 20 to 50 ohms for a quarter-wave antenna. It is known that such an antenna as Inverted V, due to the influence of the Earth and other objects, never turns out to be strictly symmetrical. And most often, the radiation resistance of 50 ohms is shifted from the middle. (One shoulder should be shortened, and the other should be increased by the same amount.) So, for example, three counterweights slightly shorter than a quarter wave, located at an angle of 120 degrees in the horizontal and vertical planes, turn the GP resistance into a very convenient 50 Ohm for us. And in general, the antenna resistance is more often “customized” to the resistance of the transmission line than vice versa, although such options are also known. This parameter is very important when designing the antenna feed unit. Not specialists and not very experienced radio amateurs, for example, I don’t even realize that not all active elements in multi-band antennas can be physically connected! For example, a very common design, when only two or even one element is connected directly to the feeder, and the rest are excited by reradiation. There is even a slang word for this - “pollination”. Of course, this is no better than the direct excitation of vibrators, but it is very economical and greatly simplifies the design and weight. An example is the numerous designs of tri-band antennas of the Uda-Yagi type. Russian Yagas including. Active nutrition of all elements is a classic, so to speak. All scientifically, maximum bandwidth without blockages, much better radiation pattern and front / back ratio. But everything good is always more expensive. And heavier :-) Therefore, a more powerful mast stretches behind it, the same turn, the area for stretch marks, etc. and so on. For us, consumers, cost is not the last argument :-). We should not forget about such a technique as symmetry. It is necessary to eliminate the "skew" when feeding a balanced antenna with an unbalanced power line (in our case, a coaxial cable) and makes significant changes to the reactive component of the resistance, bringing it closer to a purely active one.

In practice, this is either a special transform

a torus called a balun (balance-unbalance) or simply a number of ferrite rings worn on the cable near the antenna connection point. Please note that when we say "balun-transformer", we mean that in this case the impedance is actually transformed, and if it is just a balun, then rather it is a choke included in the cable braid circuit. Usually, even for a range of 80 meters, a dozen rings are enough (cable size, permeability of something from 1000 NN and less). On the higher ranges and even less. If the cable is thin, and there are one or more rings of large diameter, you can do the opposite: wind several turns of cable around the ring(s). Important: of all the turns that fit, half must be wound in the other direction. I have 10 turns of cable on a 1000NN ring on the dipole of the 80-meter range (Fig. 5), and on a three-band hexabeam (spider) there are 20 rings put on the cable. Their total resistance (as inductance) at the operating frequency must be more than 1 kiloOhm. This will prevent current from flowing through the cable sheath, thereby achieving symmetrical excitation at the connection point.

The most practical solution, which is used everywhere due to its simplicity and efficiency, is 6-10 turns of the power cable into a coil with a diameter of 20 centimeters (the turns should be fixed either on the frame or with plastic guides so that an inductance is obtained, not a cable bay :-). You can see it well in the photo. This trick will work great on your regular dipole as well. Give it a try and you will immediately notice the difference in TVI levels.

Gain

If the antenna radiates the same power in absolutely all directions, it is called isotropic. Those. radiation pattern - sphere, ball. In reality, such an antenna does not exist, so it can also be called virtual. She has only one element - she has no gain. The concept of "gain" can apply only to multi-element antennas, it is formed due to the re-emission of common-mode electromagnetic waves and the addition of signals on the active element. We are all familiar with the situation bad connection mobile phones in the countryside? And how do we solve it? We find a long conductive object and bring the “mobile” to it as close as possible. The quality of the connection is improving. Of course, due to the re-emission of the signals of the base station by the conductive object found by us. Older ones may remember a similar situation with transistor radios in the 60s. Listened to the Beatles. Same situation. This was especially noticeable on magnetic antennas: due to the large number of turns of the magnetic antenna, the summed reradiated voltage was greater. As a special case, sometimes the word "gain" is used in relation to a single pin to determine how much the vertical component of the radiation is less than the radiation in the horizontal plane. A priori, this is not a gain - it is rather a transformation factor :-) Do not confuse with phased or collinear verticals: they have two or more elements, and they have a real gain. The gain can be obtained by concentrating the radiation energy in one direction. The amplification is formed due to the addition-subtraction of radio waves excited in the vibrator and re-emitted by the director. In the animated drawing, the resulting wave is shown in green.

Directional gain (DRF) is a measure of the increase in power flow due to the compression of the radiation pattern in any one direction. An antenna can have a high directivity factor, but a low gain, if the ohmic losses in it are large and “eat up” the useful voltage obtained due to reradiation. The gain is calculated by comparing the voltage at the measured antenna with the voltage at a reference half-wave dipole operating at the same frequency as the measured antenna and at the same distance from the transmitter. Usually the gain is expressed in decibels with respect to the reference dipole - dB. More precisely, it will be called dBd. But if compared with a virtual, isotropic antenna, then the value will be expressed in dBi and the number itself will be somewhat larger, because the dipole still has some directional properties - maxima in the direction perpendicular to the canvas, if you remember, but an isotropic antenna does not . The denominator has a smaller number, so the ratio is larger. But you don’t “enter” them, we are practitioners, we always look at dBd. This is how we gradually approached the concept

radiation pattern

Antennas are trying to be designed in such a way that they have a maximum gain (receive and transmit) in a pre-selected direction. This property is called directionality. The animation shows a dynamic drawing of the addition-subtraction of radio waves excited in the vibrator and re-emitted by the reflector and the director. The resulting radio wave is shown in green. The nature of the radiation of the antenna in space is described by the radiation pattern. In addition to radiation in the main (main) direction, there are side radiation - back and side lobes.

The radiation pattern of a transmitting antenna can be plotted by rotating it and measuring the field strength at a fixed distance, without changing the transmit frequency. These measurements, converted into graphical form, give an idea in which direction the antenna has the maximum gain, i.e. the polar diagram shows the direction in which the energy radiated by the antenna is concentrated in the horizontal and vertical planes. In amateur radio practice, this is the most difficult type of measurement. When carrying out measurements in the near zone, it is necessary to take into account a number of factors affecting the reliability of measurements. Any antenna except the main lobe also has a number of side lobes; in the short wave range, we cannot raise the antenna to a great height. When measuring the radiation pattern in the HF range, the side lobe, reflected from the Earth or from a nearby building, can hit the measuring probe, both in phase and in antiphase, which will lead to an error in the measurements.

There is also a radiation pattern for simple wire antennas. For example, a dipole has a figure eight with deep dips in the diagram, which is not good. The same with the popular antenna Inv. V. If everyone remembers textbooks on radio engineering or Rothammel well, then the inverted V (dipole) has an eight diagram. Those. there are deep gaps. And if you change the position of the canvases, swap one pair (shift the canvases of one antenna, for example, at an angle of 90 degrees), then the diagram begins to approach, relatively speaking, a thick sausage. But the most important thing is that the dips disappear, and the diagram is "rounded". For a dipole, it is enough to change the angle between the halves. And if we make this angle equal to 90 ° at the wave dipole, then with some stretch the radiation diagram can be called circular.

Bandwidth

As a rule, two classes of antennas are distinguished: narrowband and broadband. It is very important that a good match and a given gain be maintained in the operating frequency range. The bandwidth of the antenna should not change when changing the frequency of the transmitter or receiver. Narrowband antennas include all simple resonant antennas, as well as directional antennas such as "wave channel" and "square". As an avid telegraphist, I am quite satisfied with antennas with a band of 100 kHz, but there are generalists, SSB lovers, so antenna manufacturers are trying to provide a bandwidth equal to the width of amateur radio sections. For example, a wave channel antenna for the 14 MHz amateur radio band must have a bandwidth of at least 300 kHz (14000 - 14300 kHz) and, moreover, good matching in this frequency band. Broadband antennas are characterized by a large frequency range, in which the operating properties of the antenna are maintained, which is many times superior to resonant systems in this respect. These include log-periodic and helical antennas.

Efficiency factor (COP)

Part of the power supplied to the antenna is radiated into space, and the other part is converted into heat in the antenna conductors. Therefore, the antenna can be represented as an equivalent load resistance consisting of two parallel components: radiation resistance and loss resistance. The efficiency of an antenna is characterized by its efficiency or the ratio of useful (radiated) power to the total power supplied to the antenna. The greater the radiation resistance in relation to the loss resistance, the greater the KGID of the antenna. It is quite obvious that good electrical contacts and small ohmic resistances (element thickness) are good.

SWR

As you can see, this parameter interests us in the last turn and is not the main one. (God forbid you think that its bad value can not be upset. If the SWR is more than two, this is bad). If the antenna is tuned to resonance and during the tuning we compensated for its reactivity, and matched it with the power feeder in terms of resistance, then the SWR will be equal to one. Just do not use the device built into the transceiver as an SWR meter. He's more of an indicator. Plus, the autotuner does not always turn off. And we want to know the truth. :-) And don't forget about balancing (see above). It is known that it is possible to power antennas with a coaxial cable of any length, that's why it is an unbalanced coaxial cable, but in the case when two antennas are powered by one cable, it is better to make sure that for both calculated frequencies the cable length is a multiple of half a wave. For example, for a frequency of 14.100, the cable length would be:

100 / 14.1 x 1; 2; 3; 4 etc. = 7.09m; 14.18m; 21.27m; 28.36m, etc.

For 21.100MHz respectively:

100 / 21.1 x 1; 2; 3; 4 etc. = 4.74m; 9.48m; 14.22m; 18.96m; 23.70; 28.44 etc.

Usually, people consider the minimum length of the feeder a priority, and if we calculate slightly longer lengths, we will see that for the ranges of 15 and 20 meters, the first "multiplicity" will occur with a cable length of 14.18 and 14.22 meters, the second, respectively, 28.44 meters and 28.36 meters. Those. the difference is 4 centimeters, the length of the PL259 connector. :-) We neglect this value and have one feeder for two antennas. Calculating the "multiple length" of the feeder for the ranges of 80 and 40 meters is now not difficult for you. If we have not forgotten about balancing, now we can tune the antenna with confidence that the feeder does not introduce any interference into the purity of the experiment. :-). A very good option is two double Inverted Vee on two masts: 40 and 80 + 20 and 15 meters. With this option (well, another GP at 28 MHz in case there is a passage), EN5R leaves for almost all expeditions.

Well, now we are armed with theoretical knowledge about the properties of antennas and can adequately perceive advice on their implementation and tuning. Of course, everything is theoretical, because you know better on the spot. The most popular among amateur radio antennas is the dipole. So, the initial conditions: we can raise and lower the dipole for half an hour and many times a day. Then, most likely, there is no point in wasting time on pre-setting it on the ground: it will not be difficult to do this for it to work at the height of the suspension. From preliminary theoretical knowledge, you only need information that the operating frequency of the dipole near the ground with the rise will “go up” by 5-7 percent. For example, for the 20-meter range, this is 200-300 kHz.

To tune into resonance with the operating frequency of a conventional dipole, you can use (except for the lower-cut-raise system) either a sweep generator (many people know this device under the name GKCH), or a GIR or, at worst, a GSS and an oscilloscope. It is clear that if there are no such devices, then you will have to tune the dipole sheet into resonance using an ordinary field indicator, or, as it is also called, a probe. This is an ordinary dipole with a long web of at least ten times less than the calculated length of the antenna itself, connected to a rectifier bridge (better on germanium diodes - it will respond to lower voltage), loaded on a conventional pointer device - a microammeter with a maximum scale size (to better it was visible :-) It would be better if the probe is with a circuit (filter) for the operating frequency, so as not to tune in to the neighbor's mobile phone, and with an amplifier. For example like this. It is clear that we adjust the length of the dipole according to the maximum of its radiation at the operating frequency. The minimum SWR in this case should be formed automatically. If not, we recall about symmetrization. If it doesn’t help and the SWR value is still high, you will have to remember about matching methods. Although this happens very rarely.

The next most complex composition is several dipoles over one cable. Well, read about the cable above, but you should know the following about the canvases: for their minimal influence on one another, they should be stretched at an angle of 90 degrees. If this is not possible, then after correcting the length of one, most likely, the other will also have to be corrected. Several inv V. over one cable - the option described above and differs only in that the SWR is "adjusted" to minimum value can be adjusted by adjusting the angle of inclination of the canvases in the vertical (to the mast), which, of course, is easier than the manufacture of a matching device and even simpler than another adjustment of the length of the canvas.

So, it turns out that a sequence of actions must be performed - first, the antenna is tuned to resonance, and then the minimum SWR is achieved in the required frequency band. All this is true for simple dipole antennas. And it becomes very complicated if the antenna is multi-element. In this variant, one cannot do without special devices, since it is necessary to set up not only a system with several unknowns, but also to achieve well-defined directional properties. Tuning includes measuring the main parameters of the antenna and correcting them by adjusting the linear dimensions of the antenna elements, the distances between the elements, adjusting the matching and balancing devices.

"I would love to help Bill, but my SWR is one on all bands..."

Tip: trust the experts. As the famous Belarusian shortwave Vladimir Prikhodko EW8AU said, “by tuning the antenna only by SWR, you can make a good matched load for the output stage of the transmitter from the antenna. It will work well in normal mode, only the antenna may have a poor radiation pattern, low efficiency, part of the power will be spent on heating the elements of the antenna and the antenna-feeder path, and the most unpleasant thing that can be for a radio amateur is television interference " .

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Or Electronic pill. The time has passed when we remembered everything... :-(Today, the combination of forgetfulness and lightning strikes has led to significant material losses. The problem is that in the countryside where I live, even houses are made of brick at best. There are practically no metal fittings in the walls, i.e. there is no electric screen, and the communication lines to the house are often laid not even with a cable, but with an ordinary two-wire wire. in such conditions, all these wires turn into lightning antennas.And since all my equipment is ultimately tied to these wires, and antennas are added, my household is very susceptible to the elements.In November, I hoped that the thunderstorms had already disappeared with the summer. In a word, twice for 100 bucks even when I had an Icom746 PRO, 600 hryvnias for replacing the UniCOM Dual interface and even flying into the Icome soundport in ACC2. on ACC2. And it turned out to be enough discharge from the tip of the connector to the braid past audio cable. In a word, even if I did not forget to pull out the antenna connector from the transceiver, there were losses. Therefore I found electronic way sclerosis treatment. Or maybe I didn’t find it, but I remembered ... :-)

It just so happened that by the New Year I had reached a milestone from which I can authoritatively tell about the new opportunities that Internet receivers provide. A few years before that, I occasionally wrote that it's good that when our passage ends, it begins on the other side of the Earth. The fact that if you can't hear anything on your 80-ke, sit on CQ, and listen to WEB SDR in the country. The fact that when a satellite goes out of your line of sight, it falls into the field of view of a neighbor .... In a word, the Internet has already been paid for anyway, so why not fasten it to our needs? What prompted me to write this material is the lists of active (permanently working) SDR receivers. Figuratively speaking, this is the sum of collective intelligence and altruistic enthusiasm - to give people the opportunity to use their antennas and receivers for their money.

Continuing the topic about SDR whistles and their advantages. Rather, regarding the shortcomings :-) The main one - the AGC works from signals in the 3 MHz band :-) I already wrote about adding signals to both HF and VHF because I find it interesting to listen to broadband receivers that can "chew" not only the spectrum of signals in the range from 0 to 2 GHz but also skimming there. Who has not been interested in the word skimmer so far, look at Wiki. But I think that everyone has looked at the Reverse Beacon System website at least once. Quite by chance, in my portfolio for a month there were two new photos that correspond to the topic :-) How to make one skimmer program (one computer :-) spy on several bands at once? Look, it's easy.