Buying a good antenna for the country is not always advisable. Especially if it is visited from time to time. It's not so much the cost, but the fact that after a while it may not be in place. Therefore, many people prefer to make an antenna for giving their own. The cost is minimal and the quality is good. And the most important point - a do-it-yourself TV antenna can be made in half an hour or an hour and then, if necessary, it can be easily repeated ...
Digital television in DVB-T2 format is transmitted in the UHF range, and there is either a digital signal or it is not. If the signal is received, then the picture is of good quality. Due to this. for reception digital television any decimeter antenna is suitable. Many radio amateurs are familiar with the TV antenna, which is called "zigzag" or "eight". This do-it-yourself TV antenna is assembled in just a matter of minutes.
To reduce the amount of interference, a reflector is placed behind the antenna. The distance between the antenna and the reflector is selected experimentally - according to the "purity" of the picture 
You can attach foil to the glass and get a good signal .... 
Copper tube or wire is the best option, it bends well, it is easy to
Making it is very simple, the material is any conductive metal: tube, rod, wire, strip, corner. She accepts, despite the simplicity, well. It looks like two squares (rhombuses) connected to each other. In the original, a reflector is located behind the square - for more confident signal reception. But it is more needed for analog signals. To receive digital television, it is quite possible to do without it or install it later if the reception is too weak.
materials
Optimum for this homemade television antenna, copper or aluminum wire with a diameter of 2-5 mm is suitable. In this case, everything can be done in just an hour. You can also use a tube, a corner, a strip of copper or aluminum, but you will need some kind of device to bend the frames of the desired shape. The wire can be bent with a hammer, fixing it in a vise.
You will also need a coaxial antenna cable of the required length, a plug suitable for the connector on your TV, some kind of mount for the antenna itself. The cable can be taken with a resistance of 75 ohms and 50 ohms (the second option is worse). If you make a TV antenna with your own hands for installation on the street, pay attention to the quality of the insulation.
Mounting depends on where you are going to hang a homemade antenna for digital television. On the upper floors, you can try to use it as a home and hang it on curtains. Then you need large pins. In the country or if you take a home-made television antenna to the roof, you will need to attach it to a pole. For this case, look for suitable clamps. To work, you will also need a soldering iron, sandpaper and / or a file, a needle file.
Do you need a calculation
To receive a digital signal, there is no need to count the wavelength. It is simply desirable to make the antenna more broadband - in order to receive as many signals as possible. To do this, some changes have been made to the original design (pictured above) (further in the text).
You can do the calculation if you want. To do this, you need to find out on which wave the signal is broadcast, divide by 4 and get the required side of the square. To get the required distance between the two parts of the antenna, make the outer sides of the diamonds a little longer, the inner ones shorter.
Drawing of the G8 antenna for receiving digital TV
- The length of the "inner" side of the rectangle (B2) is 13 cm,
- "outer" (B1) - 14 cm.
Due to the difference in lengths, the distance between the squares is formed (they should not be connected). The two extreme sections are made 1 cm longer - so that you can roll the loop to which the coaxial antenna cable is soldered.
Frame making
If you count all the lengths, you get 112 cm. We cut off the wire or the material that you have, take the pliers and the ruler, and begin to bend. The angles should be at 90° or so. With the lengths of the sides, you can make a little mistake - this is not fatal. It turns out like this:
- The first section is 13 cm + 1 cm per loop. The loop can be bent immediately.
- Two sections of 14 cm.
- Two 13 cm each, but with a turn in the opposite direction - this is the place of the inflection to the second square.
- Again two 14 cm.
- The last one is 13 cm + 1 cm per loop.
Actually the antenna frame is ready. If everything was done correctly, a distance of 1.5-2 cm was obtained between the two halves in the middle. There may be slight discrepancies. Next, we clean the loops and the place of the inflection to bare metal (treat with fine-grained emery), tin. Connect two loops, compress with pliers to hold tight.
Cable preparation
We take the antenna cable, carefully clean it. How to do this is shown in a step-by-step photo. Strip the cable on both sides. One end will be attached to the antenna. Here we clean it so that the wire sticks out 2 cm. If it turned out more, the excess (later) can be cut off. Twist the screen (foil) and braid into a bundle. It turned out two conductors. One is the central monocore of the cable, the second is twisted from a multitude of braid wires. Both are needed and need to be tinned.
Solder the plug to the second edge. There is enough length of 1 cm or so. Also form two conductors, tin.
The plug in those places where we will carry out soldering, wipe it with alcohol or a solvent, clean it with emery (you can use a needle file). Put the plastic part of the plug on the cable, now you can start soldering. We solder a monocore to the central outlet of the plug, and a stranded twist to the side outlet. The last thing is to crimp the grip around the insulation.
Then you can simply wind the plastic tip, you can fill it with glue or non-conductive sealant (this is important). While the glue / sealant has not hardened, we quickly assemble the plug (we wind the plastic part), remove the excess composition. So the plug will be almost eternal.
DIY DVB-T2 TV antenna: assembly
Now it remains to connect the cable and frame. Since we were not tied to a specific channel, we will solder the cable to the midpoint. This will increase the bandwidth of the antenna - more channels will be received. Therefore, we solder the second cut end of the cable to the two sides in the middle (those that were stripped and tinned). Another difference from the “original version” is that the cable does not need to be looped around the frame and soldered at the bottom. This will also expand the reception range.
The assembled antenna can be checked. If the reception is normal, you can finish the assembly - fill the soldering points with sealant. If the reception is poor, try to find a place where you can catch better first. If there are no positive changes, you can try replacing the cable. For ease of experiment, you can use ordinary telephone noodles. She's worth every penny. Solder the plug and the frame to it. Try with her. If it "catches" better, it's a bad cable. In principle, you can work on "noodles", but not for long - it will quickly become unusable. It is better, of course, to put a normal antenna cable.
To protect the junction of the cable and the antenna frame from atmospheric influences, the soldering points can be wrapped with ordinary electrical tape. But this is not a reliable way. If you remember, you can put on a few heat shrink tubes before soldering to insulate with their help. But the most reliable way is to fill everything with glue or sealant (they should not conduct current). As a "case" you can use covers for 5-6 liter water bottles, ordinary plastic covers for cans, etc. We make recesses in the right places - so that the frame “lays down” in them, do not forget about the cable outlet. Fill with sealing compound, wait until it seizes. Everything, a do-it-yourself TV antenna for receiving digital television is ready.
Homemade antenna double and triple square
This is a narrowband antenna, which is used when you need to receive a weak signal. It can even help if a weaker signal is "clogged" by a stronger one. The only drawback is that you need an exact orientation to the source. The same design can be done to receive digital television.
You can make five frames - for a more confident reception 
It is undesirable to paint or varnish - reception worsens. This is possible only in close proximity to the transmitter. 
The advantages of this design are that the reception will be confident even at a considerable distance from the repeater. Only it will be necessary to specifically find out the frequency of broadcasting, to withstand the dimensions of the frames and the matching device.
Construction and materials
Make it from tubes or wire:
- 1-5 TV channel of the MV range - tubes (copper, brass, aluminum) with a diameter of 10-20 mm;
- 6-12 TV channel of the MV range - tubes (copper, brass, aluminum) 8-15 mm;
- UHF range - copper or brass wire with a diameter of 3-6 mm.
The double square antenna consists of two frames connected by two arrows - upper and lower. The smaller frame is a vibrator, the larger one is a reflector. An antenna consisting of three frames gives a greater gain. The third, smallest, square is called the director.
The upper arrow connects the middle of the frames, it can be made of metal. The lower one is made of insulating material (textolite, gettinax, wooden plank). Frames should be installed so that their centers (crossing points of the diagonals) are on the same straight line. And this line should be directed to the transmitter.
The active frame - the vibrator - has an open circuit. Its ends are screwed to a textolite plate measuring 30 * 60 mm. If frames are made from a tube, the edges are flattened, holes are made in them and the lower arrow is attached through them.
The mast for this antenna must be wooden. In any case, the upper part of it. Moreover, the wooden part should begin at a distance of at least 1.5 meters from the level of the antenna frames.
Dimensions
All dimensions for the manufacture of this TV antenna with your own hands are shown in the tables. The first table is for the meter range, the second is for the decimeter range.
In three-frame antennas, the distance between the ends of the vibrator (middle) frame is made larger - 50 mm. Other dimensions are given in the tables.
Connecting an active frame (vibrator) via a short-circuited loop
Since the frame is a symmetrical device, and you need to connect it to an unbalanced coaxial antenna cable, you need a matching device. In this case, a balancing short-circuited loop is usually used. It is made from pieces of antenna cable. The right segment is called the “loop”, the left one is called the “feeder”. A cable is attached to the junction of the feeder and the cable, which goes to the TV. The length of the segments is selected based on the wavelength of the received signal (see table).
A short piece of wire (loop) is cut at one end by removing the aluminum screen and twisting the braid into a tight bundle. Its center conductor can be cut to insulation, as it does not matter. Divide and feeder. Here, too, the aluminum screen is removed and the braid is twisted into a bundle, but the central conductor remains.
Further assembly goes like this:
- The braid of the loop and the central conductor of the feeder are soldered to the left end of the active frame (vibrator).
- The feeder braid is soldered to the right end of the vibrator.
- The lower end of the loop (braid) is connected to the feeder braid using a rigid metal jumper (you can use a wire, just make sure that it makes good contact with the braid). In addition to the electrical connection, it also sets the distance between the sections of the matching device. Instead of a metal jumper, you can twist the braid of the lower part of the cable into a bundle (remove the insulation in this area, remove the screen, roll it into a bundle). To ensure good contact, solder the bundles together with low-melting solder.
- The pieces of cable must be parallel. The distance between them is about 50 mm (some deviations are possible). To fix the distance, clamps made of a dielectric material are used. You can also attach a matching device to a textolite plate, for example.
- The cable going to the TV is soldered to the bottom of the feeder. The braid is connected to the braid, the center conductor is connected to the center conductor. To reduce the number of connections, the feeder and cable to the TV can be made one. Only in the place where the feeder should end should the insulation be removed so that a jumper can be installed.
This matching device allows you to get rid of interference, a blurry contour, a second blurry image. It is especially useful at a great distance from the transmitter, when the signal will be clogged with interference.
Another variant of the triple square
In order not to connect a short-circuited loop, the triple square antenna vibrator is made elongated. In this case, you can connect the cable directly to the frame as shown in the figure. Only the height at which the antenna wire is soldered is determined in each case individually. After the antenna is assembled, “tests” are carried out. Connect the cable to the TV, move the center conductor and the braid up / down, achieving best image. In the position where the picture will be most clear, the antenna cable taps are soldered, the soldering points are isolated. The position can be any - from the bottom jumper to the transition to the frame.
Sometimes one antenna does not give the desired effect. The signal turns out to be a weak image - black and white. In this case, the standard solution is to install a TV signal amplifier.
The simplest antenna for giving - from metal cans
To make this television antenna, in addition to the cable, you will only need two aluminum or tin cans and a piece of wooden plank or plastic pipe. Banks must be metal. You can take beer aluminum, you can - tin. The main condition is that the walls are even (not ribbed).
Banks are washed and dried. The end of the coaxial wire is cut - by twisting the strands of the braid and cleaning the central core from insulation, two conductors are obtained. They are attached to banks. If you know how, you can solder. No - take two small self-tapping screws with flat caps (you can use “fleas” for drywall), twist a loop at the ends of the conductors, thread a self-tapping screw with a washer installed on it, screw it to the bank. Just before that, you need to clean the metal of the can - removing the plaque with fine-grained sandpaper.
Banks are fixed on the bar. The distance between them is selected individually - according to the best picture. You should not hope for a miracle - there will be one or two channels in normal quality, or maybe not ... It depends on the position of the repeater, the "cleanliness" of the corridor, how correctly the antenna is oriented ... But as an exit in an emergency - this is a great option.
A simple Wi-Fi antenna from a metal can
Antenna for receiving wifi signal can also be made from improvised means - from a tin can. This do-it-yourself TV antenna can be assembled in half an hour. This is if everything is done slowly. The jar should be made of metal, with smooth walls. Tall and narrow cans are great. If you put a homemade antenna on the street, find a jar with a plastic lid (as in the photo). The cable is taken antenna, coaxial, with a resistance of 75 ohms.
In addition to the can and cable, you will also need:
- radio frequency connector RF-N;
- a piece of copper or brass wire with a diameter of 2 mm and a length of 40 mm;
- cable with a socket suitable for a Wi-Fi card or adapter.
The Wi-Fi transmitters operate on the 2.4 GHz frequency with a wavelength of 124 mm. So, it is advisable to choose a jar such that its height is at least 3/4 of the wavelength. For this case, it is better that it be more than 93 mm. The diameter of the jar should be as close as possible to half the wavelength - 62 mm for a given channel. There may be some deviations, but the closer to the ideal, the better.
Dimensions and Assembly
When assembling, a hole is made in the bank. It must be placed exactly at the right point. Then the signal will be amplified several times. It depends on the diameter of the selected can. All parameters are given in the table. Measure exactly the diameter of your jar, find the right line, have all the right sizes.
| D - diameter | Lower limit of attenuation | Upper damping limit | LG | 1/4 LG | 3/4 LG |
|---|---|---|---|---|---|
| 73 mm | 2407.236 | 3144.522 | 752.281 | 188.070 | 564.211 |
| 74 mm | 2374.706 | 3102.028 | 534.688 | 133.672 | 401.016 |
| 75 mm | 2343.043 | 3060.668 | 440.231 | 110.057 | 330.173 |
| 76 mm | 2312.214 | 3020.396 | 384.708 | 96.177 | 288.531 |
| 77 mm | 2282.185 | 2981.170 | 347.276 | 86.819 | 260.457 |
| 78 mm | 2252.926 | 2942.950 | 319.958 | 79.989 | 239.968 |
| 79 mm | 2224.408 | 2905.697 | 298.955 | 74.738 | 224.216 |
| 80 mm | 2196.603 | 2869.376 | 282.204 | 070.551 | 211.653 |
| 81 mm | 2169.485 | 2833.952 | 268.471 | 67.117 | 201.353 |
| 82 mm | 2143.027 | 2799.391 | 256.972 | 64.243 | 192.729 |
| 83 mm | 2117.208 | 2765.664 | 247.178 | 61.794 | 185.383 |
| 84 mm | 2092.003 | 2732.739 | 238.719 | 59.679 | 179.039 |
| 85 mm | 2067.391 | 2700.589 | 231.329 | 57.832 | 173.497 |
| 86 mm | 2043.352 | 2669.187 | 224.810 | 56.202 | 168.607 |
| 87 mm | 2019.865 | 2638.507 | 219.010 | 54.752 | 164.258 |
| 88 mm | 1996.912 | 2608.524 | 213.813 | 53.453 | 160.360 |
| 89 mm | 1974.475 | 2579.214 | 209.126 | 52.281 | 156.845 |
| 90 mm | 1952.536 | 2550.556 | 204.876 | 51.219 | 153.657 |
| 91 mm | 1931.080 | 2522.528 | 201.002 | 50.250 | 150.751 |
| 92 mm | 1910.090 | 2495.110 | 197.456 | 49.364 | 148.092 |
| 93 mm | 1889.551 | 2468.280 | 194.196 | 48.549 | 145.647 |
| 94 mm | 1869.449 | 2442.022 | 191.188 | 47.797 | 143.391 |
| 95 mm | 1849.771 | 2416.317 | 188.405 | 47.101 | 141.304 |
| 96 mm | 1830.502 | 2391.147 | 185.821 | 46.455 | 139.365 |
| 97 mm | 1811.631 | 2366.496 | 183.415 | 45.853 | 137.561 |
| 98 mm | 1793.145 | 2342.348 | 181.169 | 45.292 | 135.877 |
| 99 mm | 1775.033 | 2318.688 | 179.068 | 44.767 | 134.301 |
The procedure is as follows:
You can do without an RF connector, but with it everything is much simpler - it is easier to set the emitter vertically upwards, connect the cable that goes to the router (router) or Wi-Fi card.
Today, almost all homes are connected to cable or satellite TV, and almost all channels go to good quality. But what if you just rent an apartment? Here a homemade antenna for digital television will come to the rescue - as a reliable and inexpensive alternative to the factory one. How it is done, read on.
To make the indicated device, you will have to use plywood 550 by 70 mm, several self-tapping screws, and a copper forty-centimeter wire 40 cm long ( central vein- 4 mm in diameter).
The basis of the product is a board. Next, cut 8 pieces of wire, the length of which is 375 mm, while they should be stripped in the center by 20-30 mm. This is necessary to ensure good contact in signal transmission.
Now, cut out 2 wires, the length of which is 220 mm and, based on the size of the plank, they should be stripped where the connections will be. After that, the remaining wires (eight pieces) must be bent so that they acquire a “V” shape.
An antenna for digital television is absolutely no different from a conventional decimeter antenna.
First, you should start buying a special plug, after which the antenna and cable should be connected to it. This is easy enough. With a desktop soldering iron, the plug is attached to the wire. This cable is installed over the bottom connection of the instrument. At this stage, the production of the antenna can be considered completed. She's ready to be turned on.
an antenna for digital television is absolutely no different from a conventional decimeter one.
The second method of making a digital television antenna from cans
Here, we will not use the finished device as a basis. The device will be completely assembled from improvised means. A homemade antenna for digital television is made using:
- wooden trempel;
- adhesive tape or electrical tape;
- soldering iron;
- two tin cans;
- several meters of wire (about 3-5 m);
- plugs.
First, you need to finalize the standard television cable. To do this, you need to slightly incise its soft shell. Under the shell, you will see a silvery "foil". This material covers the cable with several layers. For this reason, in order to see the wire itself, you will need to cut off about 10 cm from the edge. After that, the foil layer should be twisted in order to make a cut of its middle layer by about 10 mm. The reverse end of the cord is equipped with a plug used to connect to a TV.
Finished with the cable, banks are next in line. If we talk about dimensions, then a tin container with a volume of 750-1000 mm is enough to receive a digital signal. The end of the wire that is with the “foil” is attached to one bank (otherwise, the channel display will be incorrect). The core of the cable is screwed onto the second can. It is preferable to connect the cable and cans by soldering. If the wire is fixed with adhesive tape, most likely the product will not work.
The only use case for this material is when cans are placed on top of the trempel. However, even here it is impossible to deviate from the technology of application. Namely, the location of the cans should form a straight line. Tin containers should be located at a distance of about 7-8 cm from one another.
That's all, a homemade antenna for digital television is ready. Now you can start searching for a suitable signal and fixing your device. Such an antenna will allow you to view several channels, up to 10-15, if the signal is not password protected.
Video: homemade antenna for digital television
Despite the rapid development of satellite and cable television, the reception of on-air broadcasting is still relevant, for example, for places of seasonal residence. It is not at all necessary to buy a finished product for this purpose; a home decimeter (UHF) antenna can be assembled by hand. Before proceeding to the consideration of designs, we will briefly describe why this particular range of the television signal was chosen.
Why DMV?
There are two good reasons to opt for this type of structure:
- The thing is that most channels are broadcast in this range, since the design of repeaters is simplified, and this makes it possible to install a larger number of unattended low-power transmitters and thereby expand the coverage area.
- This range is selected for broadcasting "numbers".
Indoor antenna for TV "Rhombus"
This simple, but at the same time, reliable design was one of the most common in the heyday of on-air television.
Rice. 1. The simplest homemade Z-antenna, known under the names: "Rhombus", "Square" and "People's Zigzag"As can be seen from the sketch (B Fig. 1), the device is a simplified version of the classic zigzag (Z-design). To increase the sensitivity, it is recommended to equip it with capacitive inserts ("1" and "2"), as well as a reflector ("A" in Fig. 1). If the signal level is acceptable, this is not necessary.
As a material, you can use aluminum, copper, as well as brass tubes or strips with a width of 10-15 mm. If you plan to install the structure on the street, then it is better to abandon aluminum, since it is susceptible to corrosion. Capacitive inserts are made of foil, tin or metal mesh. After installation, they are soldered along the contour.
The cable is laid as shown in the figure, namely: it did not have sharp bends and did not leave the limits of the side insert.
Decimeter antenna with amplifier
In places where a powerful relay tower is not located in relative proximity, you can raise the signal level to an acceptable value using an amplifier. Below is circuit diagram device that can be used with almost any antenna.
Rice. 2. Scheme antenna amplifier for UHF range Item List:
- Resistors: R1 - 150 kOhm; R2 - 1 kOhm; R3 - 680 Ohm; R4 - 75 kOhm.
- Capacitors: C1 - 3.3 pF; C2 - 15 pF; C3 - 6800 pF; C4, C5, C6 - 100 pF.
- Transistors: VT1, VT2 - GT311D (can be replaced with: KT3101, KT3115 and KT3132).
Inductance: L1 - is a frameless coil with a diameter of 4 mm, wound with copper wire Ø 0.8 mm (2.5 turns must be made); L2 and L3 are 25 µH and 100 µH high frequency chokes, respectively.
If the circuit is assembled correctly, we will get an amplifier with the following characteristics:
- bandwidth from 470 to 790 MHz;
- gain and noise coefficients - 30 and 3 dB, respectively;
- the value of the output and input resistance of the device corresponds to the RG6 cable - 75 Ohm;
- the device consumes about 12-14 mA.
Let's pay attention to the way the power is supplied, it is carried out directly through the cable.
This amplifier can work with the simplest designs made from improvised means.
Indoor antenna made from beer cans
Despite the unusual design, it is quite functional, since it is a classic dipole, especially since the dimensions of a standard can are perfect for the arms of a UHF vibrator. If the device is installed in a room, then in this case it is not even necessary to coordinate with the cable, provided that it is not longer than two meters.
Designations:
- A - two cans with a volume of 500 mg (if you take tin, not aluminum, you can solder the cable, and not use self-tapping screws).
- B - places for fastening the shielding braid of the cable.
- C - central vein.
- D - the place of attachment of the central core
- E - cable coming from the TV.
The arms of this exotic dipole must be mounted on a holder made of any insulating material. As such, you can use improvised things, for example, a plastic clothes hanger, a mop bar, or a piece of wooden beam of the appropriate size. The distance between the shoulders is from 1 to 8 cm (selected empirically).
The main advantages of the design are fast production (10 - 20 minutes) and quite acceptable quality of the "picture", provided that the signal strength is sufficient.
Making a copper wire antenna
There is a design that is much simpler than the previous version, which requires only a piece of copper wire. This is a narrow band loop antenna. This solution has undeniable advantages, since in addition to its main purpose, the device plays the role of a selective filter that reduces interference, which allows you to confidently receive a signal.
Fig.4. A simple UHF loop antenna for receiving digital TV For this design, it is necessary to calculate the length of the loop, to do this, you need to find out the frequency of the “numbers” for your region. For example, in St. Petersburg it is broadcast on 586 and 666 MHz. The calculation formula will be as follows: L R = 300/f, where L R is the length of the loop (the result is presented in meters), and f is the average frequency range, for Peter this would be 626 (the sum of 586 and 666 divided by 2). Now we calculate L R, 300/626 = 0.48, which means that the length of the loop should be 48 centimeters.
If you take a thick RG-6 cable, where there is a braided foil, then it can be used instead of copper wire to make a loop.
Now we will tell you how the structure is assembled:
- A piece of copper wire (or RG6 cable) is measured and cut off with a length equal to L R .
- A loop of a suitable diameter is folded, after which a cable is soldered to its ends, which goes to the receiver. If RG6 is used instead of copper wire, then the insulation is first removed from its ends, by about 1-1.5 cm (the central core does not need to be cleaned, it does not participate in the process).
- The loop is installed on the stand.
- An F connector (plug) is screwed onto the cable to the receiver.
Note that despite the simplicity of the design, it is most effective for receiving "numbers", provided that the calculations are carried out correctly.
Do-it-yourself indoor antenna MV and UHF
If, in addition to UHF, there is a desire to receive MV, you can assemble a simple multiwave oven, its drawing with dimensions is presented below.
To amplify the signal in this design, a ready-made SWA 9 block is used, if there are problems with its acquisition, you can use a home-made device, the circuit of which was given above (see Fig. 2).
It is important to observe the angle between the petals, going beyond the specified range significantly affects the quality of the "picture".
Despite the fact that such a device is much simpler than a log-periodic design with a wave channel, nevertheless, it shows good results if the signal is of sufficient power.
Do-it-yourself figure-eight antenna for digital TV
Consider another common design option for receiving "numbers". It is based on the classic scheme for the UHF range, which, due to its shape, was called the "Eight" or "Zigzag".
Rice. 6. Sketch and implementation of the digital eight Construction dimensions:
- the outer sides of the rhombus (A) - 140 mm;
- inner sides (B) - 130 mm;
- distance to the reflector (C) - from 110 to 130 mm;
- width (D) - 300 mm;
- step between the bars (E) - from 8 to 25 mm.
The cable connection point is at points 1 and 2. The requirements for the material are the same as for the Rhombus design, which was described at the beginning of the article.
Homemade antenna for DBT T2
Actually, all the examples listed above are capable of receiving DBT T2, but for a change, we will give a sketch of another design, popularly called the “Butterfly”.
As a material, you can use plates made of copper, brass, aluminum or duralumin. If the structure is planned to be installed on the street, then the last two options are not suitable.
Outcome: which option to stop?
Oddly enough, but the simplest option is the most effective, so the "loop" is best suited for receiving the "digit" (Fig. 4). But, if you want to receive other channels in the decimeter range, then it is better to stop at the "Zigzag" (Fig. 6).
The antenna for the TV should be directed towards the nearest active repeater, to select the desired position, rotate the structure until the signal strength is satisfactory.
If, despite the presence of an amplifier and a reflector, the quality of the “picture” leaves much to be desired, you can try to install the structure on the mast.
In this case, it is necessary to install lightning protection, but this is a topic for another article.
On summer cottages a television signal can rarely be received without amplification: too far from the repeater, the terrain is usually uneven, and trees interfere. For the normal quality of the “picture”, antennas are needed. Anyone who knows how to handle a soldering iron at least a little can make an antenna for giving with his own hands. Aesthetics outside the city is given not so great importance, the main thing is the reception quality, simple design, low cost and reliability. You can experiment and do it yourself.
A simple TV antenna
If the repeater is located within 30 km from your dacha, you can make the simplest receiving part in design. These are two identical tubes connected by a cable. The output of the cable is fed to the corresponding input of the TV.
The design of the antenna for the TV in the country: it is very easy to do it yourself (to increase the size of the picture, click on it with the left mouse button)
What you need to make this TV antenna
First of all, you need to find out what frequency the nearest TV tower is broadcasting on. The length of the "whiskers" depends on the frequency. The broadcast band is in the range of 50-230 MHz. It is divided into 12 channels. Each needs its own length of tubes. List of terrestrial television channels, their frequencies and television antenna parameters for self-manufacturing will result in a table.
| Channel number | Channel frequency | Vibrator length - from one to the other end of the tubes, cm | Length of cables for matching device, L1/L2 cm |
|---|---|---|---|
| 1 | 50 MHz | 271-276 cm | 286 cm / 95 cm |
| 2 | 59.25 MHz | 229-234 cm | 242 cm / 80 cm |
| 3 | 77.25 MHz | 177-179 cm | 187 cm / 62 cm |
| 4 | 85.25 MHz | 162-163 cm | 170 cm / 57 cm |
| 5 | 93.25 MHz | 147-150 cm | 166 cm / 52 cm |
| 6 | 175.25 MHz | 85 cm | 84 cm / 28 cm |
| 7 | 183.25 MHz | 80 cm | 80 cm / 27 cm |
| 8 | 191.25 MHz | 77 cm | 77 cm / 26 cm |
| 9 | 199.25 MHz | 75 cm | 74 cm / 25 cm |
| 10 | 207.25 MHz | 71 cm | 71 cm / 24 cm |
| 11 | 215.25 MHz | 69 cm | 68 cm / 23 cm |
| 12 | 223.25 MHz | 66 cm | 66 cm / 22 cm |
So, in order to make a TV antenna with your own hands, you need the following materials:
It would be nice to have a soldering iron, flux for soldering copper and solder on hand: it is advisable to solder all the connections of the central conductors: the image quality will be better and the antenna will work longer. The places of soldering then need to be protected from oxidation: it is best to fill it with a layer of silicone, you can use epoxy, etc. As a last resort, seal it with electrical tape, but this is very unreliable.
This homemade TV antenna, even at home, will be made by a child. You need to cut the tube of the length that matches the broadcast frequency of the nearby repeater, then cut it exactly in half.
Assembly order
The resulting tubes are flattened on one side. With these ends they are attached to the holder - a piece of getinax or textolite 4-6 mm thick (see figure). The tubes are placed at a distance of 6-7 cm from each other, their far ends should be at the distance indicated in the table. They are fixed to the holder with clamps, they must hold firmly.
The installed vibrator is fixed on the mast. Now you need to connect two "whiskers" through a matching device. This is a cable loop with a resistance of 75 ohms (type RK-1, 3, 4). Its parameters are indicated in the rightmost column of the table, and how it is done is on the right side of the photo.
The middle cores of the cable are screwed (soldered) to the flattened ends of the tubes, their braid is connected with a piece of the same conductor. It is easy to get the wire: cut off a piece from the cable a little more than the required size and free it from all shells. Strip the ends and screw to the cable conductors (it is better to solder).
Then the central conductors from two pieces of the matching loop and the cable that goes to the TV are connected. Their braid is also connected with a copper wire.
The last action: the loop in the middle is attached to the bar, and the cable going down is screwed to it. The bar is raised to the required height and “tuned” there. Two people are needed to set up: one turns the antenna, the second watches TV and evaluates the picture quality. Having determined where the signal is best received from, the do-it-yourself antenna is fixed in this position. In order not to suffer for a long time with the "tuning", look where the neighbors' receivers (terrestrial antennas) are directed. The simplest antenna for giving with your own hands is made. Set and "catch" the direction by turning it along its axis.
Watch the video on how to cut a coaxial cable.
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Loop from a pipe
This do-it-yourself antenna is a little more difficult to manufacture: you need a pipe bender, but the reception radius is larger - up to 40 km. The starting materials are almost the same: a metal tube, a cable and a rod.
The bend radius of the pipe is not important. It is necessary that the pipe has the required length, and the distance between the ends is 65-70 mm. Both "wings" should be the same length, and the ends should be symmetrical about the center.
Homemade antenna for a TV: a TV signal receiver with a reception radius of up to 40 km is made from a piece of pipe and cable (to increase the size of the picture, click on it with the left mouse button)
The length of the pipe and cable is shown in the table. Find out at what frequency the repeater closest to you is broadcasting, select the appropriate line. Saw off the pipe of the required size (diameter is preferably 12-18 mm, for them the parameters of the matching loop are given).
| Channel number | Channel frequency | Vibrator length - from one end to the other, cm | Cable length for matching device, cm |
|---|---|---|---|
| 1 | 50 MHz | 276 cm | 190 cm |
| 2 | 59.25 MHz | 234 cm | 160 cm |
| 3 | 77.25 MHz | 178 cm | 125 cm |
| 4 | 85.25 MHz | 163 cm | 113 cm |
| 5 | 93.25 MHz | 151 cm | 104 cm |
| 6 | 175.25 MHz | 81 cm | 56 cm |
| 7 | 183.25 MHz | 77 cm | 53 cm |
| 8 | 191.25 MHz | 74 cm | 51 cm |
| 9 | 199.25 MHz | 71 cm | 49 cm |
| 10 | 207.25 MHz | 69 cm | 47 cm |
| 11 | 215.25 MHz | 66 cm | 45 cm |
| 12 | 223.25 MHz | 66 cm | 44 cm |
Assembly
The tube of the required length is bent, making it absolutely symmetrical about the center. One edge is flattened and brewed / sealed. Fill with sand, and close up the second side. If there is no welding, you can plug the ends, just put the plugs on good glue or silicone.
The resulting vibrator is fixed on the mast (rod). They are screwed to the ends of the pipe, and then the central conductors of the matching loop and the cable that goes to the TV are soldered. The next step is to connect a piece of copper wire without insulation to the braid of the cables. The assembly is completed - you can proceed to the "configuration".
beer can antenna
Despite the fact that she looks frivolous, the image becomes much better. Checked multiple times. Try it!
Beer can outdoor antenna
We collect like this:
- We drill a hole in the bottom of the jar strictly in the center (5-6 mm in diameter).
- Through this hole we stretch the cable, we bring it out through the hole in the cover.
- We fix this jar on the left on the holder so that the cable is directed to the middle.
- We take out the cable from the can by about 5-6 cm, remove the insulation by about 3 cm, disassemble the braid.
- We cut the braid, its length should be about 1.5 cm.
- We distribute it over the surface of the can and solder it.
- The central conductor sticking out by 3 cm must be soldered to the bottom of the second can.
- The distance between the two banks must be made as small as possible, and fixed in some way. One option is sticky tape or duct tape.
- That's it, the homemade UHF antenna is ready.
End the other end of the cable with a suitable plug, plug it into the TV socket you need. This design, by the way, can be used to receive digital television. If your TV supports this signal format (DVB T2) or there is a special set-top box for an old TV, you can catch a signal from the nearest repeater. You just need to find out where it is and direct your own television antenna made from tin cans there.
Simple homemade antennas can be made from cans (from beer or drinks). Despite the frivolity of the "components", it works very well, and is made very simply.
The same design can be adapted to receive VHF channels. Instead of 0.5 liter jars, put on 1 liter. Will receive MW band.
Another option: if you don’t have a soldering iron, or you don’t know how to solder, you can make it easier. Tie two cans at a distance of a few centimeters to the holder. Strip the end of the cable by 4-5 centimeters (carefully remove the insulation). Separate the braid, twist it into a bundle, make a ring out of it, into which you insert a self-tapping screw. From the central conductor, make a second ring and thread the second self-tapping screw through it. Now, at the bottom of one can, you clean (with sandpaper) a speck to which you screw the screws.
In fact, soldering is needed for better contact: it is better to tin and solder the braid ring, as well as the place of contact with the metal of the can. But even on self-tapping screws it turns out well, however, the contact is periodically oxidized and needs to be cleaned. As it "snows" you will know why ...
Do-it-yourself digital TV antenna
Antenna design - frame. For this version of the receiver, you will need a crosspiece made of wooden boards and a television cable. You will also need electrical tape, a few nails. All.
We have already said that to receive a digital signal, you only need a decimeter terrestrial antenna and an appropriate decoder. It can be built into TVs (new generation) or made as a separate device. If the TV has a signal reception function in the DVB T2 code, connect the antenna output directly to the TV. If your TV does not have a decoder, you will need to purchase digital set-top box and connect the output from the antenna to it, and connect it to the telly.
How to determine the channel and calculate the perimeter of the frames
In Russia, a program has been adopted, according to which towers are constantly being built. By the end of 2015, the entire area should be covered by repeaters. On the official website http://xn--p1aadc.xn--p1ai/when/ find the closest tower to you. It shows the broadcast frequency and channel number. The perimeter of the antenna frame depends on the channel number.
For example, channel 37 broadcasts at a frequency of 602 MHz. The wavelength is considered as follows: 300 / 602 \u003d 50 cm. This will be the perimeter of the frame. Let's calculate the other channel in the same way. Let it be channel 22. Frequency 482 MHz, wavelength 300/482 = 62 cm.
Since this antenna consists of two frames, the length of the conductor must be equal to twice the wavelength, plus 5 cm per connection:
- for channel 37 we take 105 cm of copper wire (50 cm * 2 + 5 cm = 105 cm);
- for 22 channels you need 129 cm (62 cm * 2 + 5 cm = 129 cm).
Assembly
Copper wire is best used from the cable that will go further to the receiver. That is, take the cable and remove the sheath and braid from it, freeing the central conductor of the desired length. Be careful not to damage it.
- for channel 37: 50 cm / 4 = 12.5 cm;
- for 22 channels: 62 cm / 4 = 15.5 cm.
The distance from one nail to another must correspond to these parameters. The laying of copper wire starts on the right, from the middle, moving down and further along all points. Only in the place where the frames come close to one another, do not short the conductors. They should be at some distance (2-4 cm).
When the entire perimeter is laid, the braid from a cable a few centimeters long is twisted into a bundle and soldered (wound if it is not possible to solder) to the opposite edge of the frame. Next, the cable is laid as shown in the figure, winding it with electrical tape (more often, but the laying route cannot be changed). Then the cable goes to the decoder (separate or built-in). All the antenna for giving with your own hands for receiving digital television is ready.
How to make an antenna for digital television with your own hands - another design - is shown in the video.
Once a good television antenna was in short supply, purchased quality and durability, to put it mildly, did not differ. Making an antenna for a “box” or “coffin” (an old tube TV) with your own hands was considered an indicator of skill. Interest in homemade antennas does not fade away even today. There is nothing strange here: TV reception conditions have changed dramatically, and manufacturers, believing that there is and will not be anything essentially new in the theory of antennas, most often adapt electronics to well-known designs, without thinking about the fact that The main thing for any antenna is its interaction with the signal on the air.
What has changed on the air?
Firstly, almost the entire volume of TV broadcasting is currently carried out in the UHF band. First of all, for economic reasons, it greatly simplifies and reduces the cost of the antenna-feeder economy of transmitting stations, and, more importantly, the need for its regular maintenance by highly qualified specialists engaged in hard, harmful and dangerous work.
Second - TV transmitters now cover almost all more or less populated places with their signal, and a developed communication network ensures the delivery of programs to the most remote corners. There, broadcasting in the habitable zone is provided by low-power, unattended transmitters.
Third, the conditions for the propagation of radio waves in cities have changed. On the UHF, industrial interference leaks weakly, but reinforced concrete high-rise buildings for them are good mirrors, repeatedly reflecting the signal until it is completely attenuated in the zone of seemingly confident reception.
Fourth - There are a lot of TV programs on the air now, dozens and hundreds. How diverse and meaningful this set is is another question, but it is now meaningless to count on receiving 1-2-3 channels.
Finally, development of digital broadcasting. The DVB T2 signal is something special. Where it still exceeds the noise even a little, by 1.5-2 dB, the reception is excellent, as if nothing had happened. And a little further or to the side - no, as cut off. The “digit” is almost insensitive to interference, but if there is a mismatch with the cable or phase distortions anywhere in the path, from the camera to the tuner, the picture can crumble into squares even with a strong clean signal.
Antenna Requirements
In accordance with the new reception conditions, the basic requirements for TV antennas have also changed:
- Its parameters such as directivity coefficient (DAC) and protective action coefficient (CPA) do not have a decisive value now: modern ether is very dirty, and along the tiny side lobe of the radiation pattern (DN), at least some kind of interference, yes, it will crawl through, and it is necessary to deal with it by means of electronics.
- Instead, the intrinsic gain of the antenna (KU) is of particular importance. An antenna that “catches” the air well, and does not look at it through a small hole, will provide a power reserve for the received signal, allowing the electronics to clear it of noise and interference.
- A modern television antenna, with rare exceptions, must be a band antenna, i.e. its electrical parameters should be kept in a natural way, at the level of theory, and not squeezed into acceptable limits by engineering tricks.
- The TV antenna must be coordinated in the cable over its entire operating frequency range without additional devices matching and balancing (USS).
- The frequency response of the antenna (AFC) should be as smooth as possible. Sharp surges and dips are inevitably accompanied by phase distortions.
The last 3 points are due to admission requirements digital signals. Customized, i.e. operating theoretically at the same frequency, antennas can be "stretched" in frequency, for example. antennas of the "wave channel" type on the UHF with an acceptable signal-to-noise ratio capture channels 21-40. But their coordination with the feeder requires the use of OSS, which either strongly absorb the signal (ferrite), or spoil the phase response at the edges of the range (tuned). And such an antenna, which works perfectly on an “analog”, will receive a “digit” badly.
In this regard, from all the great antenna variety, this article will consider TV antennas available for self-manufacturing, of the following types:
- Frequency independent (all-wave)- does not differ in high parameters, but is very simple and cheap, it can be done in just an hour. Outside the city, where the air is cleaner, it will be able to receive a digital or a fairly powerful analogue not a short distance from the television center.
- Range log-periodic. Figuratively speaking, it can be likened to a fishing trawl, which sorts prey when it is caught. It is also quite simple, perfectly consistent with the feeder in its entire range, absolutely does not change the parameters in it. The technical parameters are average, therefore it is more suitable for giving, and in the city as a room.
- Several modifications of the zigzag antenna, or Z-antennas. In the MV range, this is a very solid design that requires considerable skill and time. But on the UHF, due to the principle of geometric similarity (see below), it is so simplified and shrinks that it can be used as a highly efficient indoor antenna under almost any reception conditions.
Note: The Z-antenna, to use the previous analogy, is a frequent nonsense, raking up everything that is in the water. As the air became littered, it fell out of use, but with the development of digital TV, it again found itself on a horse - in its entire range it is just as perfectly coordinated and keeps the parameters as a “speech therapist”.
Precise matching and balancing of almost all the antennas described below is achieved by laying the cable through the so-called. point of zero potential. It has special requirements, which will be discussed in more detail below.
About vibrator antennas
Up to several tens of digital channels can be transmitted in the frequency band of one analog channel. And, as already mentioned, the figure works with an insignificant signal-to-noise ratio. Therefore, in places very remote from the television center, where the signal of one or two channels barely finishes, for receiving digital TV, the good old wave channel (AVK, wave channel antenna) from the class of vibrator antennas can also be used, so at the end we will devote a few lines and to her.
About satellite reception
There is no point in making a satellite dish yourself. You still need to buy a head and a tuner, and behind the external simplicity of the mirror lies a parabolic oblique incidence surface, which not every industrial enterprise can perform with the required accuracy. The only thing that homemade people can do is set up a satellite dish, about that.
About antenna parameters
The exact determination of the antenna parameters mentioned above requires knowledge of higher mathematics and electrodynamics, but it is necessary to understand their meaning when starting to manufacture an antenna. Therefore, we give a somewhat rough, but still clarifying definition (see the figure on the right):
- KU - the ratio of the signal power received by the antenna to the main (main) lobe of its DN, to its same power, received in the same place and at the same frequency, omnidirectional, with a circular, DN, antenna.
- KND is the ratio of the solid angle of the entire sphere to the solid angle of the opening of the main lobe of the RP, assuming that its cross section is a circle. If the main lobe has different sizes in different planes, you need to compare the area of the sphere and the cross-sectional area of \u200b\u200bthe main lobe.
- CPD is the ratio of the signal power received to the main lobe to the sum of the interference powers at the same frequency received by all side (back and side) lobes.
Notes:
- If the antenna is a band antenna, the powers are considered at the frequency of the useful signal.
- Since there are no completely omnidirectional antennas, a half-wave linear dipole oriented in the direction of the electric field vector (along its polarization) is taken as such. Its KU is considered equal to 1. TV programs are transmitted with horizontal polarization.
It should be remembered that KU and KND are not necessarily interconnected. There are antennas (for example, "spy" - a single-wire traveling wave antenna, ABC) with high directivity, but unity or less gain. Such look into the distance as if through a diopter sight. On the other hand, there are antennas, eg. Z-antenna, in which low directivity is combined with significant gain.
About the intricacies of manufacturing
All elements of the antennas, through which the currents of the useful signal flow (specifically, in the descriptions of individual antennas), must be interconnected by soldering or welding. In any prefabricated assembly in the open air, electrical contact will soon be broken, and the parameters of the antenna will deteriorate sharply, up to its complete uselessness.
This is especially true for points of zero potential. In them, as experts say, there is a voltage node and current antinode, i.e. its greatest value. Current at zero voltage? Nothing surprising. Electrodynamics has gone from Ohm's law to DC as far as a T-50 from a kite.
Places with zero potential points for digital antennas are best made from bent solid metal. A small "creeping" current in welding when receiving an analogue in the picture, most likely, will not affect. But, if a figure is received at the noise boundary, then the tuner may not see the signal due to the “creep”. Which, with a pure current in the antinode, would give a stable reception.
About cable soldering
The braid (and often the central core) of modern coaxial cables are not made of copper, but of corrosion-resistant and inexpensive alloys. They solder badly and if you heat for a long time, you can burn the cable. Therefore, you need to solder cables with a 40-watt soldering iron, low-melting solder and with flux paste instead of rosin or alcohol rosin. There is no need to spare the paste, the solder immediately spreads along the veins of the braid only under a layer of boiling flux.
Types of antennas
All-wave
An all-wave (more precisely, frequency-independent, CNA) antenna is shown in fig. She is two triangular metal plates, two wooden slats, and a lot of enameled copper wires. The diameter of the wire does not matter, and the distance between the ends of the wires on the rails is 20-30 mm. The gap between the plates to which the other ends of the wires are soldered is 10 mm.
Note: instead of two metal plates, it is better to take a square of one-sided foil fiberglass in triangles cut out on copper.
The width of the antenna is equal to its height, the opening angle of the canvases is 90 degrees. The cable laying diagram is shown in the same place in Fig. The point marked in yellow is the point of quasi-zero potential. It is not necessary to solder the cable sheath to the web in it, it is enough to tie it tightly, for coordination there will be enough capacity between the braid and the web.
CNA, stretched in a window 1.5 m wide, receives all meter and DCM channels from almost all directions, except for a dip of about 15 degrees in the canvas plane. This is its advantage in places where it is possible to receive signals from different television centers, it does not need to be rotated. Disadvantages - a single KU and zero KZD, therefore, in the zone of interference and outside the zone of reliable reception, the CHNA is not suitable.
Note : There are other types of NNA, for example. in the form of a two-turn logarithmic spiral. It is more compact than triangular canvases in the same frequency range, therefore it is sometimes used in technology. But in everyday life this does not give advantages, it is more difficult to make a spiral CNA, it is more difficult to coordinate with a coaxial cable, therefore we do not consider it.
Based on the CNA, a once very popular fan vibrator (horns, flyer, slingshot) was created, see fig. Its directivity and efficiency are something around 1.4 with a fairly smooth frequency response and linear phase response, so it would be suitable for digital even now. But - it works only on MV (channels 1-12), and digital broadcasting goes to UHF. However, in the countryside, when climbing 10-12 m, it can be suitable for receiving an analogue. The mast 2 can be made of any material, but the mounting straps 1 are made of a good non-wetting dielectric: fiberglass or fluoroplast with a thickness of at least 10 mm.
Beer all-wave
The all-wave antenna made of beer cans is clearly not the fruit of the hangover hallucinations of a drunken radio amateur. This is really a very good antenna for all reception cases, you just need to make it right. And extremely simple.
Its design is based on the following phenomenon: if you increase the diameter of the arms of a conventional linear vibrator, then its operating frequency band expands, while other parameters remain unchanged. Since the 1920s, long-distance radio communications have been using the so-called. Nadenenko dipole based on this principle. And beer cans are just right in size as the arms of a vibrator on the UHF. In essence, the PNA is a dipole, the arms of which expand indefinitely to infinity.
The simplest beer vibrator of two cans is suitable for indoor reception of an analogue in the city, even without coordination with the cable, if its length is not more than 2 m, on the left in fig. And if you assemble a vertical in-phase array from beer dipoles with a half-wave step (on the right in the figure), match it and balance it with the help of an amplifier from the Polish antenna (we will talk about it later), then due to the vertical compression of the main lobe of the DN, such an antenna will give and good ku.
The gain of the “pivnukha” can be further increased by adding at the same time a KZD, if a screen from the grid is placed behind it at a distance equal to half the grating pitch. A beer grate is mounted on a dielectric mast; mechanical connections of the shield with the mast are also dielectric. The rest is clear from the next. rice.
Note: the optimal number of lattice floors is 3-4. With 2, the gain in gain will be small, and more difficult to match with the cable.
Video: manufacturing the simplest antenna from beer cans
"Speech therapist"
A log-periodic antenna (LPA) is a collecting line to which halves of linear dipoles (i.e., pieces of a conductor a quarter of the working wavelength) are alternately connected, the length and distance between which change exponentially with an exponent less than 1, in the center in Fig. The line can be either configured (with a short circuit at the end opposite the cable connection point) or free. An LPA on a free (unconfigured) line is preferable for receiving a digit: it comes out longer, but its frequency response and phase response are smooth, and matching with the cable does not depend on frequency, so we will stop at it.
LPA can be manufactured for any, up to 1-2 GHz, predetermined frequency range. When the operating frequency changes, its active region of 1-5 dipoles shifts back and forth along the canvas. Therefore, the closer the progression indicator is to 1, and, accordingly, the smaller the antenna opening angle, the greater the gain it will give, but at the same time its length increases. On the UHF, 26 dB can be achieved from an external LPA, and 12 dB from a room one.
LPA, we can say, in terms of the combination of qualities, an ideal digital antenna, so let's dwell on its calculation in more detail. The main thing to know is that an increase in the progression rate (tau in the figure) gives an increase in gain, and a decrease in the opening angle of the LPA (alpha) increases directivity. The screen for the LPA is not needed, it has almost no effect on its parameters.
The calculation of a digital LPA has the following features:
- They start it, for the sake of frequency margin, from the second longest vibrator.
- Then, taking the reciprocal of the progression rate, the longest dipole is calculated.
- After the shortest, based on the given frequency range, dipole, add one more.
Let's explain with an example. Let's say our digital programs are in the range of 21-31 TVK, i.e. at 470-558 MHz in frequency; wavelengths, respectively - 638-537 mm. Let's also assume that we need to receive a weak noisy signal far from the station, so we take the maximum (0.9) progression indicator and the minimum (30 degrees) opening angle. For the calculation, you need half the opening angle, i.e. 15 degrees in our case. Opening can be further reduced, but the length of the antenna will increase exorbitantly, in terms of cotangent.
We consider B2 in Fig: 638/2 = 319 mm, and the dipole arms will be 160 mm each, you can round up to 1 mm. The calculation will need to be carried out until Bn = 537/2 = 269 mm is obtained, and then another dipole is calculated.
Now we consider A2 as B2 / tg15 \u003d 319 / 0.26795 \u003d 1190 mm. Then, through the progression indicator, A1 and B1: A1 = A2 / 0.9 = 1322 mm; B1 \u003d 319 / 0.9 \u003d 354.5 \u003d 355 mm. Then sequentially, starting with B2 and A2, we multiply by the indicator until we reach 269 mm:
- B3 \u003d B2 * 0.9 \u003d 287 mm; A3 \u003d A2 * 0.9 \u003d 1071 mm.
- H4 = 258 mm; A4 = 964 mm.
Stop, we already have less than 269 mm. We check whether we meet the gain, although it’s already clear that we don’t: in order to get 12 dB or more, the distances between the dipoles should not exceed 0.1-0.12 wavelengths. In this case, we have for B1 A1-A2 \u003d 1322 - 1190 \u003d 132 mm, and this is 132/638 \u003d 0.21 of the wavelength of B1. It is necessary to “pull up” the indicator to 1, to 0.93-0.97, so we try different ones until the first difference A1-A2 is halved or more. For a maximum of 26 dB, you need a distance between dipoles of 0.03-0.05 wavelengths, but not less than 2 dipole diameters, 3-10 mm on UHF.
Note: the rest of the line behind the shortest dipole, we cut it off, it is needed only for calculation. Therefore, the actual length of the finished antenna will be only about 400 mm. If our LPA is outdoor, this is very good: you can reduce the opening, getting more directivity and protection from interference.
Video: DVB T2 Digital TV Antenna
About line and mast
The diameter of the tubes of the LPA line on the DMV is 8-15 mm; the distance between their axes is 3-4 diameters. We also take into account that thin “lace-up” cables give such attenuation per meter to the UHF that all antenna-amplifying tricks will come to naught. The coaxial for the outdoor antenna must be taken good, with a shell diameter of 6-8 mm. That is, the tubes for the line must be thin-walled seamless. It is impossible to tie the cable to the line from the outside, the quality of the LPA will drop sharply.
It is necessary, of course, to fasten the outer LPA to the mast by the center of gravity, otherwise the low windage of the LPA will turn into a huge and shaking one. But it is also impossible to connect a metal mast directly to the line: it is necessary to provide a dielectric insert at least 1.5 m long. The quality of the dielectric does not play a big role here, the oiled and painted wood will do.
About the Delta Antenna
If the UHF LPA is consistent with the amplifier cable (see below, about Polish antennas), then the shoulders of a meter dipole, linear or fan-shaped, can be attached to the line, like a "slingshot". Then we get a universal MV-UHF antenna of excellent quality. This solution is used in the popular Delta antenna, see fig.
Antenna "Delta"
Zigzag on air
The Z-antenna with a reflector gives the same gain and QPV as the LPA, but its main lobe is more than twice as wide horizontally. This may be important in the countryside, when there is TV reception from different directions. And the decimeter Z-antenna has small dimensions, which is essential for indoor reception. But its operating range is theoretically not unlimited, frequency overlap while maintaining parameters acceptable for digital - up to 2.7.
The design of the MV Z-antenna is shown in Figure; the cable path is highlighted in red. In the same place at the bottom left - a more compact ring version, colloquially - a "spider". It clearly shows that the Z-antenna was born as a combination of a CNA with a range vibrator; there is something in it from a rhombic antenna, which does not fit into the topic. Yes, the spider ring does not have to be wooden, it can be a metal hoop. "Spider" receives 1-12 MV channels; DN without a reflector is almost circular.
The classic zigzag works either on 1-5 or 6-12 channels, but for its manufacture you only need wooden slats, copper enameled wire c d = 0.6-1.2 mm and a few scraps of foil fiberglass, so we give dimensions, through shot for 1-5/6-12 channels: A = 3400/950 mm, B, C = 1700/450 mm, b = 100/28 mm, B = 300/100 mm. At point E - zero potential, here you need to solder the braid with a metallized base plate. The reflector dimensions are also 1-5/6-12: A = 620/175 mm, B = 300/130 mm, D = 3200/900 mm.
A range Z-antenna with a reflector gives a gain of 12 dB, tuned to one channel - 26 dB. In order to build a single-channel zigzag based on a range zigzag, you need to take the side of the square of the canvas in the middle of its width to a quarter of the wavelength and recalculate all other dimensions proportionally.
folk zigzag
As you can see, the MV Z-antenna is a rather complex structure. But its principle shows itself in all its splendor in the DMV. The UHF Z-antenna with capacitive inserts, which combines the advantages of "classics" and "spider", is so easy to make that it earned the title of people's in the USSR, see fig.
Material - copper tube or aluminum sheet with a thickness of 6 mm. The side squares are solid metal or covered with a mesh, or closed with a tin. In the last two cases, they need to be soldered along the contour. The coax cannot be bent sharply, so we guide it so that it reaches the side corner, and then does not go beyond the capacitive insert (side square). At point A (zero potential point), we electrically connect the cable sheath to the web.
Note: aluminum is not soldered with conventional solders and fluxes, therefore aluminum "folk" is suitable for outdoor installation only after sealing the electrical connections with silicone, because everything is screwed in it.
Video: Dual Delta Antenna Example
wave channel
The wave channel antenna (AVK), or the Udo-Yagi antenna available for self-production, is capable of giving the highest KU, KND and KZD. But it can receive a figure on the UHF only on 1 or 2-3 adjacent channels, tk. belongs to the class of sharply tuned antennas. Its parameters outside the tuning frequency deteriorate sharply. VKA is recommended to be used with very poor reception conditions, and for each TVK, make a separate one. Luckily, it's not very difficult - AVK is simple and cheap.
At the heart of the work of the AVC is the "raking" of the electromagnetic field (EMF) of the signal to the active vibrator. Outwardly small, light, with minimal windage, AVK can have an effective aperture of tens of wavelengths of operating frequency. Shortened and therefore having a capacitive impedance (impedance) directors (directors) direct the EMF to the active vibrator, and the reflector (reflector), elongated, with an inductive impedance, throws back to it what slipped by. Only 1 reflector is needed in AVK, but there can be from 1 to 20 or more directors. The more of them, the higher the amplification of the AVC, but the narrower its frequency band.
From the interaction with the reflector and directors, the wave impedance of the active (from which the signal is taken) of the vibrator drops the more, the closer the antenna is tuned to the gain maximum, and coordination with the cable is lost. Therefore, the active dipole AVK is made loop, its initial impedance is not 73 ohms, as in a linear one, but 300 ohms. At the cost of reducing it to 75 ohms, an AVC with three directors (five-element, see the figure on the right) can be tuned to almost a maximum gain of 26 dB. Characteristic for AVC RP in the horizontal plane is shown in fig. at the beginning of the article.
AVK elements are connected to the boom at zero potential points, so the mast and boom can be anything. Polypropylene pipes work very well.
The calculation and setting of AVK for analog and digital are somewhat different. For an analogue, the wave channel must be calculated for the carrier frequency of the image F and for a digital one, for the middle of the TVK spectrum Fc. Why so - here to explain, unfortunately, there is no place. For the 21st TVK Fi = 471.25 MHz; Fc = 474 MHz. UHF TVK are located close to each other through 8 MHz, so their tuning frequencies for AVC are calculated simply: Fn = Fi / Fc (21 TVK) + 8 (N - 21), where N is the number of the desired channel. Eg. for 39 TVK Fi = 615.25 MHz, and Fc = 610 MHz.
In order not to write down a lot of numbers, it is convenient to express the dimensions of the AVC in fractions of the operating wavelength (it is considered as L \u003d 300 / F, MHz). The wavelength is usually denoted by the small Greek letter lambda, but since there is no Greek alphabet by default on the Internet, we will conditionally denote it with a large Russian letter L.
The dimensions of the AVK optimized for the figure, according to Fig., are as follows:
- P = 0.52L.
- B \u003d 0.49L.
- D1 = 0.46L.
- D2 = 0.44L.
- D3 \u003d 0.43 l.
- a = 0.18L.
- b = 0.12L.
- c \u003d d \u003d 0.1L.
If you do not need a lot of gain, but it is more important to reduce the dimensions of the AVK, then D2 and D3 can be removed. All vibrators are made of a tube or rod with a diameter of 30-40 mm for 1-5 TVK, 16-20 mm for 6-12 TVK and 10-12 mm for UHF.
AVK requires precise matching with the cable. It is the careless implementation of the matching and balancing device (USS) that explains most of the failures of amateurs. The simplest CSS for AVK is a U-loop from the same coaxial cable. Its design is clear from Fig. on right. The distance between the signal terminals 1-1 is 140 mm for 1-5 TVK, 90 mm for 6-12 TVK and 60 mm for UHF.
Theoretically, the length of the knee l should be half the length of the working wave, as it appears in most publications on the Internet. But the EMF in the U-loop is concentrated inside the cable filled with insulation, so it is necessary (for a figure - especially necessary) to take into account its shortening factor. For 75-ohm coaxes, it ranges from 1.41-1.51, i.e. l you need to take from 0.355 to 0.330 wavelengths, and take it exactly so that the AVC is an AVC, and not a set of pieces of iron. The exact value of the velocity factor is always on the cable certificate.
IN Lately the domestic industry began to produce reconfigurable AVK for digital, see fig. The idea, I must say, is excellent: by moving the elements along the boom, you can fine-tune the antenna to local reception conditions. It is better, of course, for a specialist to do this - the element-by-element setting of the AVK is interdependent, and the amateur will certainly get confused.
About "Poles" and amplifiers
For many users, Polish antennas, which previously decently received an analog, refuse to take a figure - it breaks, or even disappears altogether. The reason, I beg your pardon, is a bawdy-commercial approach to electrodynamics. It is sometimes a shame for colleagues who have made such a “miracle”: the frequency response and phase response look like either a psoriasis hedgehog, or a horse comb with broken teeth.
The only thing that is good about the "Polish women" is their amplifiers for the antenna. Actually, they do not allow these products to die ingloriously. First of all, the "bud" amplifiers are low-noise broadband. And, more importantly, with a high-impedance input. This allows, with the same strength of the EMF signal on the air, to apply several times more power to the tuner input, which makes it possible for the electronics to “tear out” the figure from the very ugly noises. In addition, due to the large input impedance, the Polish amplifier is an ideal CSS for any antenna: no matter what you connect to the input, the output is exactly 75 ohms without reflection and creep.
However, with a very poor signal, outside the zone of reliable reception, the Polish amplifier no longer pulls. Power is supplied to it via cable, and power decoupling takes away 2-3 dB of the signal-to-noise ratio, which may just not be enough for the figure to go into the very outback. Needed here good amplifier TV signal with separate power supply. It will most likely be located near the tuner, and the OSS for the antenna, if required, will have to be done separately.
The scheme of such an amplifier, which showed almost 100% repeatability even when performed by novice radio amateurs, is shown in Fig. Gain adjustment - potentiometer P1. Decoupling chokes L3 and L4 are standard purchased. Coils L1 and L2 are sized to wiring diagram on right. They are part of the bandpass signal filters, so small deviations in their inductance are not critical.
However, the topology (configuration) of the installation must be observed exactly! And in the same way, a metal shield is also required, separating the output circuits from the other circuit.
Where to begin?
We hope that even experienced craftsmen will find some useful information in this article. And for beginners who do not yet feel the ether, it is best to start with a beer antenna. The author of the article, by no means and by no means an amateur in this field, at one time was quite surprised: the simplest "beer" with ferrite matching, as it turned out, and the MV takes no worse than the tested "slingshot". And what is worth doing one and the other - see the text.
(2
ratings, average: 4,00
out of 5)
And on the roof there was a satisfactory reception for the Pole. I have 70-80 kilometers to the TV center. These are my problems. From the balcony it is possible to catch 3-4 pieces from 30 channels, and then with “cubes”. I sometimes watch TV channels from the Internet on the computer in my room, and my wife in her TV cannot watch her favorite channels normally. Neighbors advise to install cable, but you have to pay for it every month, and I already pay for the Internet, and the pension is not rubber. We pull it all, we pull it, and it’s not enough for everything.
Peter Kopitonenko said:
It is impossible to put an antenna on the roof of the house, the neighbors swear that I go and break the roofing material of the roof and then their ceiling leaks. Actually, I am very “thankful” to that economist who received a bonus for saving himself. I came up with the idea of \u200b\u200bremoving an expensive gable roof from houses and replacing it with a flat roof covered with bad roofing material. The economist received money for saving, and people on the upper floors now suffer all their lives. Water flows on their heads and on the bed. They change the roofing material every year, and it becomes unusable during the season. In frosty weather, it cracks and rainwater and snow flows into the apartment, even if no one walks on the roof!!!
Sergei said:
Greetings!
Thanks for the article, but who is the author (I don’t see the signature)?
LPA according to the above method works fine, UHF 30 and 58 channels. Tested in the city (reflected signal) and outside the city, distances to the transmitter (1 kW) respectively: 2 and 12 km approximately. Practice has shown that there is no urgent need for the “B1” dipole, but another dipole in front of the shortest has a significant effect, judging by the signal intensity in%. Especially in the conditions of the city, where it is necessary to catch (in my case) the reflected signal. only I made an antenna with a “short circuit”, it happened, it just didn’t turn out to be a suitable insulator.
In general, I recommend.
Vasily said:
IMHO: people looking for an antenna for receiving ETsTV, forget about LPA. These wide-range antennas were created in the second half of the 50s (!!) of the last century in order to catch foreign television centers while being on the shores of the Soviet Baltic. In the magazines of the time, this was bashfully called "ultra-long reception." Well, they loved to watch Swedish porn on the Riga seashore at night ...
In terms of destination, I can say the same about “double, triple, etc. squares", as well as any "zigzags".
Compared to a “wave channel” similar in range and gain, LPA is more bulky and material-intensive. The calculation of the LPA is complex, intricate and looks more like guessing and adjusting the results.
If ETsTV is broadcasting in your region on neighboring UHF channels (I have 37-38), then The best decision search online for a book: Kapchinsky L.M. TV antennas(2nd edition, 1979) and make a “wave channel” for a group of UHF channels (if you broadcast above 21-41 channels, you will have to recalculate) described on page 67 and further (Fig. 39, table 11).
If the antenna can be simplified 15 - 30 km to the transmitter by making it four - five element, simply without installing the directors D, E and G.
For very close transmitters, I recommend indoor antennas, by the way, in the same book on pages 106 - 109, drawings of wide-range indoor "wave channel" and LPA are given. The "wave channel" is visually smaller, simpler and more elegant with more gain!
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