DIY DMV antenna made from cable. Screening grid design. Antennas for digital television reception

Once upon a time, a good television antenna was in short supply; purchased ones did not differ in quality and durability, to put it mildly. Making an antenna for a “box” or “coffin” (an old tube TV) with your own hands was considered a sign of skill. Interest in homemade antennas continues to this day. There is nothing strange here: the conditions for TV reception have changed dramatically, and manufacturers, believing that there is and will not be anything significantly new in the theory of antennas, most often adapt electronics to long-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 air?

Firstly, almost the entire volume of TV broadcasting is currently carried out in the UHF range. First of all, for economic reasons, it greatly simplifies and reduces the cost of the antenna-feeder system 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 areas 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 in weakly, but reinforced concrete high-rise buildings are good mirrors for them, repeatedly reflecting the signal until it is completely attenuated in an area of ​​seemingly reliable reception.

Fourth - There are a lot of TV programs on air now, dozens and hundreds. How diverse and meaningful this set is is another question, but counting on receiving 1-2-3 channels is now pointless.

Finally, digital broadcasting has developed. The DVB T2 signal is a special thing. Where it still exceeds the noise even just a little, by 1.5-2 dB, the reception is excellent, as if nothing had happened. But a little further or to the side - no, it’s cut off. Digital is almost insensitive to interference, but if there is a mismatch with the cable or phase distortion 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 the directivity coefficient (DAC) and the protective action coefficient (PAC) are now of no decisive importance: modern air is very dirty, and along the tiny side lobe of the directional pattern (DP), at least some interference will get through, and You need to fight it using electronic means.
• In return, the antenna's own gain (GA) becomes especially important. An antenna that catches the air well, rather than looking at it through a small hole, will provide a reserve of power for the received signal, allowing the electronics to clear it of noise and interference.
• A modern television antenna, with rare exceptions, must be a range antenna, i.e. its electrical parameters must be preserved naturally, at the level of theory, and not squeezed into acceptable limits through engineering tricks.
• The TV antenna must be matched with the cable over its entire operating frequency range without additional matching and balancing devices (MCD).
• The amplitude-frequency response of the antenna (AFC) should be as smooth as possible. Sharp surges and dips are certainly accompanied by phase distortions.

The last 3 points are determined by the requirements for receiving digital signals. Customized, i.e. Working 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 USSs, 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 analogue, will receive “digital” poorly.

In this regard, from all the great variety of antennas, this article will consider TV antennas, available for self-production, of the following types:

• Frequency independent (all-wave)– does not have high parameters, but is very simple and cheap, it can be done in literally an hour. Outside the city, where the airwaves are cleaner, it will be able to receive 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 the prey during fishing. It is also quite simple, fits perfectly with the feeder throughout its entire range, and does not change its parameters at all. The technical parameters are average, so it is more suitable for a summer residence, 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 shrunk that it can well 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 dragster that scoops up everything in the water. As the air became littered, it fell out of use, but with the development of digital TV, it was once again on the high horse - throughout its entire range, it is just as perfectly coordinated and keeps the parameters as a “speech therapist.”

Precise matching and balancing of almost all antennas described below is achieved by laying the cable through the so-called. zero potential point. It has special requirements, which will be discussed in more detail below.

About vibrator antennas

In the frequency band of one analog channel, up to several dozen digital ones can be transmitted. And, as already said, the digital 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 reaches, the good old wave channel (AVK, wave channel antenna), from the class of vibrator antennas, can be used for receiving digital TV, 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 surface of oblique incidence, which not every industrial enterprise can produce with the required accuracy. The only thing that DIYers can do is set up a satellite dish; read about that here.

About antenna parameters

Accurate 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 will give somewhat rough, but still clarifying definitions (see figure on the right):

To determine antenna parameters

• KU is the ratio of the signal power received by the antenna on the main (main) lobe of its DP to its same power received in the same place and at the same frequency by an omnidirectional, circular, DP 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 DN, assuming that its cross section is a circle. If the main petal has different sizes in different planes, you need to compare the area of ​​the sphere and its cross-sectional area of ​​the main petal.
• SCR is the ratio of the signal power received at the main lobe to the sum of the interference powers at the same frequency received by all secondary (back and side) lobes.

Notes:

• If the antenna is a band antenna, the powers are calculated 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 (according to its polarization) is taken as such. Its QU is considered equal to 1. TV programs are transmitted with horizontal polarization.

It should be remembered that CG and KNI are not necessarily interrelated. There are antennas (for example, “spy” - single-wire traveling wave antenna, ABC) with high directivity, but single or lower gain. These look into the distance as if through a diopter sight. On the other hand, there are antennas, e.g. Z-antenna, which combines low directivity with significant gain.

About the intricacies of manufacturing

All antenna elements through which useful signal currents flow (specifically, in the descriptions of individual antennas) must be connected to each other by soldering or welding. In any prefabricated unit in the open air, the electrical contact will soon be broken, and the parameters of the antenna will deteriorate sharply, up to its complete unusability.

This is especially true for points of zero potential. In them, as experts say, there is a voltage node and a current antinode, i.e. its greatest value. Current at zero voltage? Nothing surprising. Electrodynamics has moved as far from Ohm's law on direct current as the T-50 has gone from a kite.

Places with zero potential points for digital antennas are best made bent from solid metal. A small “creeping” current in welding when receiving the analogue in the picture will most likely not affect it. But, if a digital signal is received at the noise level, then the tuner may not see the signal due to the “creep”. Which, with pure current at the antinode, would give stable reception.

About cable soldering

The braid (and often the central core) of modern coaxial cables is made not of copper, but of corrosion-resistant and inexpensive alloys. They solder poorly and if you heat them for a long time, you can burn out the cable. Therefore, you need to solder the cables with a 40-W 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.

Frequency independent antenna with horizontal polarization

Types of antennas
All-wave

An all-wave (more precisely, frequency-independent, FNA) antenna is shown in Fig. It consists of 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 slats 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 with triangles cut out of copper.

The width of the antenna is equal to its height, the opening angle of the blades is 90 degrees. The cable routing diagram is shown there in Fig. The point marked in yellow is the point of quasi-zero potential. There is no need to solder the cable braid to the fabric in it; just tie it tightly, and the capacity between the braid and the fabric will be enough for matching.

The CHNA, 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 plane of the canvas. 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 - single gain and zero gain, therefore, in the interference zone and outside the zone of reliable reception, the CNA is not suitable.

Note: There are other types of CNA, for example. in the form of a two-turn logarithmic spiral. It is more compact than the CNA made of triangular sheets in the same frequency range, therefore it is sometimes used in technology. But in everyday life this does not provide any advantages, it is more difficult to make a spiral CNA, and it is more difficult to coordinate with a coaxial cable, so we are not considering it.

Based on the CHNA, the once very popular fan vibrator (horns, flyer, slingshot) was created, see fig. Its directivity factor and coefficient of performance are something around 1.4 with a fairly smooth frequency response and linear phase response, so it would be suitable for digital use even now. But - it only works on HF (channels 1-12), and digital broadcasting is on UHF. However, in the countryside, with an elevation of 10-12 m, it may be suitable for receiving an analogue. Mast 2 can be made of any material, but fastening strips 1 are made of a good non-wetting dielectric: fiberglass or fluoroplastic with a thickness of at least 10 mm.

Fan vibrator for receiving MV TV

Beer all-wave

Beer can antennas

The all-wave antenna made from beer cans is clearly not the fruit of the hangover hallucinations of a drunken radio amateur. This is truly a very good antenna for all reception situations, you just need to do it right. And it’s 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, but other parameters remain unchanged. In long-distance radio communications, since the 20s, the so-called Nadenenko's dipole based on this principle. And beer cans are just the right size to serve as the arms of a vibrator on the UHF. In essence, the CHNA is a dipole, the arms of which expand indefinitely to infinity.

The simplest beer vibrator made of two cans is suitable for indoor analogue reception in the city, even without coordination with the cable, if its length is no more than 2 m, on the left in Fig. And if you assemble a vertical in-phase array from beer dipoles with a step of half a wave (on the right in the figure), match it and balance it using an amplifier from a Polish antenna (we will talk about it later), then thanks to the vertical compression of the main lobe of the pattern, such an antenna will give good CU.

The gain of the “pivnuha” can be further increased by adding a CPD at the same time, if a mesh screen is placed behind it at a distance equal to half the grid pitch. The beer grill is mounted on a dielectric mast; The mechanical connections between the screen and the mast are also dielectric. The rest is clear from the following. rice.

In-phase array of beer dipoles

Note: the optimal number of lattice floors is 3-4. With 2, the gain in gain will be small, and more is difficult to coordinate with the cable.

"Speech therapist"

A log-periodic antenna (LPA) is a collecting line to which halves of linear dipoles (i.e., pieces of conductor a quarter of the operating wavelength) are alternately connected, the length and distance between which vary in geometric progression with an index less than 1, in the center in Fig. The line can be either configured (with a short circuit at the end opposite to the cable connection) or free. An LPA on a free (unconfigured) line is preferable for digital reception: it comes out longer, but its frequency response and phase response are smooth, and the matching with the cable does not depend on frequency, so we will focus on it.

Log-periodic antenna design

The LPA can be manufactured for any predetermined frequency range, up to 1-2 GHz. When the operating frequency changes, its active region of 1-5 dipoles moves 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. At UHF, 26 dB can be achieved from an outdoor LPA, and 12 dB from a room LPA.

LPA can be said to be an ideal digital antenna based on its totality of qualities, so let’s look at its calculation in a little more detail. The main thing you need to know is that an increase in the progression indicator (tau in the figure) gives an increase in gain, and a decrease in the LPA opening angle (alpha) increases the directivity. A screen is not needed for the LPA; it has almost no effect on its parameters.

Calculation of digital LPA has the following features:

• They start it, for the sake of frequency reserve, with the second longest vibrator.
• Then, taking the reciprocal of the progression index, the longest dipole is calculated.
• After the shortest dipole based on the given frequency range, another one is added.

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, are 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 rate and the minimum (30 degrees) opening angle. For the calculation, you will need half the opening angle, i.e. 15 degrees in our case. The opening can be further reduced, but the length of the antenna will increase exorbitantly, in cotangent terms.

We consider B2 in Fig: 638/2 = 319 mm, and the arms of the dipole will be 160 mm each, you can round up to 1 mm. The calculation will need to be carried out until you get Bn = 537/2 = 269 mm, and then calculate another dipole.

Now we consider A2 as B2/tg15 = 319/0.26795 = 1190 mm. Then, through the progression indicator, A1 and B1: A1 = A2/0.9 = 1322 mm; B1 = 319/0.9 = 354.5 = 355 mm. Next, sequentially, starting with B2 and A2, we multiply by the indicator until we reach 269 mm:

• B3 = B2*0.9 = 287 mm; A3 = A2*0.9 = 1071 mm.
• B4 = 258 mm; A4 = 964 mm.

Stop, we are already less than 269 mm. We check whether we can meet the gain requirements, although it is clear that we can’t: to get 12 dB or more, the distances between the dipoles should not exceed 0.1-0.12 wavelengths. In this case, for B1 we have A1-A2 = 1322 – 1190 = 132 mm, which is 132/638 = 0.21 wavelengths of B1. We need to “pull up” the indicator to 1, to 0.93-0.97, so we try different ones until the first difference A1-A2 is reduced by half 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 at UHF.

Note: cut off the rest of the line behind the shortest dipole; it is needed only for calculations. Therefore, the actual length of the finished antenna will be only about 400 mm. If our LPA is external, this is very good: we can reduce the opening, obtaining greater directionality and protection from interference.

Video: antenna for digital TV DVB T2

About the line and the mast

The diameter of the tubes of the LPA line on the UHF is 8-15 mm; the distance between their axes is 3-4 diameters. Let’s also take into account that thin “lace” cables give such attenuation per meter on the UHF that all antenna-amplification tricks will come to naught. You need to take a good coaxial for an outdoor antenna, with a shell diameter of 6-8 mm. That is, the tubes for the line must be thin-walled, seamless. You cannot tie the cable to the line from the outside; the quality of the LPA will drop sharply.

It is necessary, of course, to attach the outer propulsion boat to the mast by the center of gravity, otherwise the small windage of the propulsion boat will turn into a huge and shaking one. But it is also impossible to connect a metal mast directly to the line: you need to provide a dielectric insert of at least 1.5 m in length. The quality of the dielectric does not play a big role here; oiled and painted wood will do.

About the Delta antenna

If the UHF LPA is consistent with the cable amplifier (see below, about Polish antennas), then the arms of a meter dipole, linear or fan-shaped, like a “slingshot”, can be attached to the line. Then we will get a universal VHF-UHF antenna of excellent quality. This solution is used in the popular Delta antenna, see fig.

Delta antenna

Zigzag on air

A Z-antenna with a reflector gives the same gain and gain as the LPA, but its main lobe is more than twice as wide horizontally. This can be important in rural areas 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 the digital range is up to 2.7.

Z-antenna MV

The design of the MV Z-antenna is shown in Fig; The cable route is highlighted in red. In the same place on the left below is a more compact ring version, colloquially known as a “spider”. It clearly shows that the Z-antenna was born as a combination of a CNA with a range vibrator; There is also something of a rhombic antenna in it, which does not fit into the theme. Yes, the “spider” ring does not have to be wooden, it can be a metal hoop. "Spider" receives 1-12 MV channels; The pattern 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, enameled copper wire with d = 0.6-1.2 mm and several scraps of foil fiberglass, so we give the dimensions in fraction 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 there is zero potential; here you need to solder the braid to a metallized support plate. Reflector dimensions, also 1-5/6-12: A = 620/175 mm, B = 300/130 mm, D = 3200/900 mm.

The range Z-antenna with a reflector gives a gain of 12 dB, tuned to one channel - 26 dB. To build a single-channel one based on a range zigzag, you need to take the side of the square of the canvas in the middle of its width at 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 glory on the UHF. The UHF Z-antenna with capacitive inserts, combining the advantages of the “classics” and the “spider”, is so easy to make that even in the USSR it earned the title of folk antenna, see fig.

People's UHF antenna

Material – copper tube or aluminum sheet with a thickness of 6 mm. The side squares are solid metal or covered with mesh, or covered with a tin. In the last two cases, they need to be soldered along the circuit. 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 braid to the fabric.

Note: aluminum cannot be soldered with conventional solders and fluxes, so “folk” aluminum is suitable for outdoor installation only after sealing the electrical connections with silicone, since everything in it is screwed.

Video: example of a double triangle antenna

Wave channel

Wave channel antenna

The wave channel antenna (AWC), or Udo-Yagi antenna, available for self-production, is capable of giving the highest gain, directivity factor and efficiency factor. But it can only receive digital signals on UHF on 1 or 2-3 adjacent channels, because belongs to the class of finely tuned antennas. Its parameters deteriorate sharply beyond the tuning frequency. It is recommended to use AVK under very poor reception conditions, and make a separate one for each TVK. Fortunately, this is not very difficult - AVK is simple and cheap.

The operation of the AVK is based on “raking” the electromagnetic field (EMF) of the signal to the active vibrator. Externally small, lightweight, with minimal windage, the AVK can have an effective aperture of dozens of wavelengths of the operating frequency. Directors (directors) that are shortened and therefore have capacitive impedance (impedance) direct the EMF to the active vibrator, and the reflector (reflector), elongated, with inductive impedance, throws back to it what has slipped past. Only 1 reflector is needed in an AVK, but there can be from 1 to 20 or more directors. The more there are, the higher the gain of the AVC, but the narrower its frequency band.

From interaction with the reflector and directors, the wave impedance of the active (from which the signal is taken) vibrator drops the more, the closer the antenna is tuned to the maximum gain, and coordination with the cable is lost. Therefore, the active dipole AVK is made into a loop, its initial wave impedance is not 73 Ohms, like a linear one, but 300 Ohms. At the cost of reducing it to 75 Ohms, an AVK with three directors (five-element, see the figure on the right) can be adjusted to almost a maximum gain of 26 dB. A characteristic pattern for AVK in the horizontal plane is shown in Fig. at the beginning of the article.

AVK elements are connected to the boom at points of zero potential, so the mast and boom can be anything. Propylene pipes work very well.

Calculation and adjustment of AVK for analog and digital are somewhat different. For analogue, the wave channel must be calculated at the carrier frequency of the image Fi, and for digital – at the middle of the TVC spectrum Fc. Why this is so - unfortunately, there is no room to explain here. For the 21st TVC Fi = 471.25 MHz; Fс = 474 MHz. UHF TVCs are located close to each other at 8 MHz, so their tuning frequencies for AVK are calculated simply: Fn = Fi/Fс(21 TVC) + 8(N – 21), where N is the number of the desired channel. Eg. for 39 TVCs 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 AVK in fractions of the operating wavelength (it is calculated as A = 300/F, MHz). The wavelength is usually denoted by the small Greek letter lambda, but since there is no default Greek alphabet on the Internet, we will conventionally denote it by the large Russian L.

The dimensions of the digitally optimized AVK, according to the figure, are as follows:

U-loop: USS for AVK

• P = 0.52L.
• B = 0.49L.
• D1 = 0.46L.
• D2 = 0.44L.
• D3 = 0.43l.
• a = 0.18L.
• b = 0.12L.
• c = d = 0.1L.

If you don’t need a lot of gain, but reducing the size of the AVK is more important, 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 TVKs, 16-20 mm for 6-12 TVKs and 10-12 mm for UHF.

AVK requires precise coordination with the cable. It is the careless implementation of the matching and balancing device (CMD) that explains most of the failures of amateurs. The simplest USS for AVK is a U-loop made from the same coaxial cable. Its design is clear from Fig. on right. The distance between signal terminals 1-1 is 140 mm for 1-5 TVKs, 90 mm for 6-12 TVKs and 60 mm for UHF.

Theoretically, the length of the knee l should be half the length of the working wave, and this is what is indicated 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 numbers - especially mandatory) to take into account its shortening factor. For 75-ohm coaxials it ranges from 1.41-1.51, i.e. l you need to take from 0.355 to 0.330 wavelengths, and take exactly so that the AVK is an AVK, and not a set of pieces of iron. The exact value of the shortening factor is always in the cable certificate.

Recently, the domestic industry has begun to produce reconfigurable AVCs for digital use, 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 adjustment of the AVC is interdependent, and an amateur will certainly get confused.

AVK for digital TV

About “Poles” and amplifiers

Many users have Polish antennas, which previously received analogue decently, but refuse to accept digital - they break or even disappear completely. The reason, I beg your pardon, is the obscene commercial approach to electrodynamics. Sometimes I feel ashamed for my colleagues who have concocted such a “miracle”: the frequency response and phase response resemble either a psoriasis hedgehog or a horse’s comb with broken teeth.

The only good thing about the Poles is their antenna amplifiers. Actually, they do not allow these products to die ingloriously. Firstly, the “belt” amplifiers are broadband, low-noise. And, more importantly, with a high-impedance input. This allows, at the same strength of the EMF signal on the air, to supply several times more power to the tuner input, which makes it possible for the electronics to “rip out” a number from very ugly noise. In addition, due to the high input impedance, the Polish amplifier is an ideal USS for any antennas: whatever you attach to the input, the output is exactly 75 Ohms without reflection or creep.

However, with a very poor signal, outside the zone of reliable reception, the Polish amplifier no longer works. Power is supplied to it via a cable, and power decoupling takes away 2-3 dB of the signal-to-noise ratio, which may not be enough for the digital signal to go right into the outback. Here you need a good TV signal amplifier with separate power supply. It will most likely be located near the tuner, and the control system for the antenna, if required, will have to be made separately.

UHF TV signal amplifier

The circuit of such an amplifier, which has shown almost 100% repeatability even when implemented by novice radio amateurs, is shown in Fig. Gain adjustment – ​​potentiometer P1. The decoupling chokes L3 and L4 are standard purchased ones. Coils L1 and L2 are made according to the dimensions in the wiring diagram on the right. They are part of signal bandpass filters, so small deviations in their inductance are not critical.

However, the installation topology (configuration) must be observed exactly! And in the same way, a metal shield is required, separating the output circuits from the other circuit.

Where to begin?

We hope that experienced craftsmen will find some useful information in this article. And for beginners who don’t yet feel the air, it’s best to start with a beer antenna. The author of the article, by no means an amateur in this field, was quite surprised at one time: the simplest “pub” with ferrite matching, as it turned out, takes the MV no worse than the proven “slingshot”. And what it costs to do both - see the text.

Equipment for digital television is what you can buy in our store. Our company has been operating in the market of broadcast and satellite equipment since 2003 and we already know most of our clients by sight.
For regular customers of our online store there is a system of discounts, which are calculated automatically according to the coupon number assigned to you personally.
All equipment undergoes pre-sale preparation, namely, the latest version of software is installed on satellite and terrestrial set-top boxes. All receivers are tested for functionality.
Our company delivers equipment both in Moscow and throughout Russia. Most courier delivery companies have agreements on preferential delivery prices.
In our online store you can find almost any equipment that you may need to receive satellite and terrestrial television. We have tried to make the ordering process convenient for anyone. If you plan to order not one item, but several, then you can use the store search and pay attention to the accompanying equipment. If you want to pick up equipment for receiving satellite TV, then you should go to the tab menu “Satellite TV”, if to receive terrestrial or cable TV, then “Terrestrial TV”, etc. If you have questions during the ordering process, you can use the online chat, which is located on each page of the online store, or request a call back.
We hope that in the online digital TV store you can spend a minimum amount of time ordering the required equipment.

Which antenna to choose for digital television? How are antennas different? How to supply power to an active antenna? Which antenna is better? These and other questions on the site

Hi all! Due to my line of work, I have to deal very closely with connecting and setting up antennas for digital terrestrial television.

Therefore, based on the experience gained, I have the opportunity to share how to choose an antenna for digital television and set up dvb-t2 - free 20 channels.

Quick navigation through the article

Which antenna is suitable for DVB-T2 digital television

With the advent of digital terrestrial television, many people have questions related to the choice of antenna for DVB-T2. For example!

• Can I use my old antenna, if I had one?
• Is an antenna of the “Lattice” type, also known as “Polish”, suitable for this?
• Do I need an antenna with or without an amplifier?
• if there is a question about purchasing a new one?
• Is the advertised “Key to Free TV” antenna necessary?

Let's first figure out what kind of antennas there are.

Antennas of the meter (MV) and decimeter (UHF) ranges are used to receive television signals. There are broadband antennas, this is a “hybrid” when elements of the MV and UHF bands are used in the antenna design.

These antennas are easy to distinguish from each other by size.

The MV range has longer elements. Everything is according to the name.

So in MV antennas the elements are approximately half a meter to one and a half meters in length.

And the elements of the UHF antenna are only about 15 to 40 cm long.

It is the UHF antenna that is needed for digital terrestrial television.

VHF Antenna
Example of a UHF antenna
Broadband antenna, MV and UHF ranges.
Array antenna
Broadband antenna "Hummingbird"

So - To receive digital terrestrial television you need a UHF antenna, i.e. antenna with short elements. Or broadband.

Now you can evaluate whether your old antenna is suitable for receiving television in the DVB -T2 format. The only question that remains open is its serviceability and effectiveness in your area.

In addition to dividing by received ranges, antennas are also divided into...

Indoor and outdoor (External) - I think everything is clear with the application here.

And also active and passive - more on that a little later.

Well, a brief excursion into the difficult topic of terrestrial antennas has been carried out. Let's continue...

Features of television signal propagation

The distance over which the signal is transmitted in the UHF range does not have a large coverage area. It is much less than in the meter range.

For example:

If you have used a radio, you may have noticed that you cannot catch distant foreign radio stations in the FM or VHF bands, but only those nearby, local ones.
But on the other hand, you can catch a whole bunch of foreign ones in the CB or HF bands.

This is because medium and short waves, like meter ones, propagate over long distances, and ultrashort waves, like UHF, over short distances.

This disadvantage of the UHF range for digital TV is compensated by the location and number of television transmitters - by analogy with cell towers, there are many of them.

Also keep in mind that the television signal is perfectly reflected from objects encountered along the way.

This allows you to receive broadcasts when it is not possible to point the antenna towards the TV tower. Or there are obstacles to the direct passage of the signal.

Look around! Is it possible to receive a reflected signal?

So if you choose the right antenna and install it correctly, you will surely achieve success.

What else should you consider when choosing an antenna?

Conditions for receiving a television signal vary greatly in different places and these conditions must be taken into account when choosing an antenna.

Here are some factors that will determine which antenna you need to purchase and how to install it.

1. TV transmitter power and
2. Terrain - mountains, lowlands, plains.
3. Standing nearby and blocking the antenna towards the tower are tall, dense trees.
4. The presence of high-rise buildings and your location in relation to these buildings and the tower.
5. The floor you live on - the higher you are, the simpler the antenna you will need.
6. Possibility or impossibility of turning the antenna towards the transmitting tower.

Active and passive antennas - what is the difference?

Antennas of any type can be either active or passive.

Passive antennas are those that amplify the signal only due to their design, without the use of electronic amplifiers; such antennas are used in areas with a strong signal.

Active antenna - has an amplifier in its design; such an antenna needs to be connected to a power source.
The amplifier helps to increase the level of the received signal in areas of poor reception.

How to connect power to an active antenna amplifier, several ways

Antenna amplifiers are powered by 12 or 5 volts. But recently, more and more, manufacturers are focused on producing antennas with five-volt power supply.

And there is a reason for this! Such antennas are easier to connect for those who use a DVB-T2 set-top box.

Three connection methods

A) Use a special power supply with a separator that produces a voltage corresponding to your amplifier.

The purpose of a separator is to separate. It passes voltage to the antenna, but does not pass it to the TV socket. However, this does not interfere with the signal from the antenna amplifier entering the TV.

B) If a DVB-T2 set-top box is used. A voltage of 5 volts can be supplied directly from the set-top box. Moreover, for any amplifiers, both 5 and 12 volts.

This does not require any additional wire, power supply, etc. The voltage is 5 volts, from the antenna socket of the set-top box, directly through the antenna cable, it will go to the amplifier.

You just need to turn on this power directly from the set-top box menu. Go to the settings section and find the item “Antenna power ON-OFF”, select ON, and exit the menu (the names of these items may differ in different models of set-top boxes)

B) If you have an LCD TV with a built-in DVB-T2 tuner, then in addition to the method under letter A) you can do the following.

You will have to purchase a special adapter to power the amplifier from any USB port; first of all, consider the USB port of the LCD TV itself. But you can connect to any charger with a USB output

Which antenna to choose - let's look at examples

As you understand from all of the above, when choosing an antenna for yourself, you need to evaluate various factors.

A few examples:

Distance to the tower 5-15 km

You live in a city where there is a DVB-T2 signal transmitter. Or in a populated area, not far from the transmitter, 5-15 km.

Most likely, an indoor antenna, even the simplest one, will be suitable for you. Especially if you live above the first floor.

And being not far from the tower, even a simple piece of wire instead of an antenna may be enough.

Considering the prevalence of towers and a fairly large number of places with a reliable signal, scammers take advantage of this, offering various, essentially

Under the conditions described above, they will work well.

But keep in mind that the number of channels will be no more than that broadcast by the TV tower in your area! But not 100 or 200 as the advertisement promises.
Therefore, the question arises: is it necessary to shell out several hundred, or even thousands, for a regular indoor antenna from an advertisement?!

Here are several inexpensive, compact antenna options for conditions where there is a good signal.

Indoor antenna for places close to the tower.
Indoor antenna for places close to the tower. Another option
This option may work in slightly more difficult conditions than the previous two, especially the amplified version.

Indoor antenna - application features

The right place for an indoor antenna is not where it will look good and stand comfortably, this is where it will receive the signal well. And these two circumstances - “look” and “accept” - do not always coincide.

Because often the best, and sometimes the only place where you can catch a signal is a place at the window facing the TV tower. Take this into account!

To solve this problem, you can add a cable of the required length, and for some antennas (for example, those in the photo above) this is not difficult.

But there are indoor antennas that have a built-in power supply in their housing. They also have a power cord for connecting to an outlet. And of course a cable for connecting to a TV.

This may seem convenient, but unfortunately this is not always the case.
Often, the place where the antenna is capable of receiving a TV signal is not at all near the TV and outlet, but, for example, near a window.

And in this case, a short power cord will become an obstacle to placing the antenna in the right place. In addition to the cable, you will also have to pull an extension cord. Basically a lot of wires.

You live at a distance of about 25-30 km or more from the TV tower.

Of course, a lot depends on the power of the transmitter.

But in general, at a distance of 25 km, a small outdoor antenna is sufficient. Like, for example, those depicted at the very beginning of this post, we mean the UHF antenna or the broadband “Hummingbird”.

In my area, from a distance of 25 km in line of sight, a passive UHF antenna with an arm length of approximately 80 cm provides reliable reception without the need to raise the antenna above two meters from the ground.

You can also receive reception using a good active indoor antenna.

In some houses, even from the first floor, if there is a window towards the tower or the ability to receive a reflected signal from neighboring buildings.
A floor above the second significantly increases the likelihood of success.

There is a simple principle on how to determine the power of an antenna - the longer the antenna arm, the greater the coefficient of its own gain, and not due to the amplifier.

Antenna for difficult signal reception conditions

For example, the active antenna in the photo below, in our area, pulls out a signal from a distance of 60 km or more. It is successfully used in the most difficult places, in houses located in deep lowlands, its length is approximately 1.7 meters, but there are antennas up to 4 meters in length.

In addition to the length, in difficult conditions or at a great distance from the TV tower, the presence of an amplifier plays an important role, i.e. the antenna must be active.

There are options for powerful antennas, where instead of one boom, three are used at once, so the ability of the antenna to amplify the signal due to the design alone is greatly increased.

And in tandem with an amplifier, this antenna becomes a very powerful trap for a television signal.

But once you’re impressed with this antenna, don’t rush to run after it. It is only needed under really, really difficult reception conditions.

In most cases, other, much cheaper options are sufficient. In addition, if the signal in your area is already strong, then the amplifier in the antenna will only interfere.

This is exactly the case when porridge can be ruined with butter. An example of this is described below.

Polish antenna array for digital television

In some cases, the “Grid” antenna can work quite successfully when receiving digital television. Especially if you are not very close to the transmitting tower.

More than once, however, I came across a situation where, using their old antenna - Polyachka (Grid), people could not get a digital broadcast signal from it.

Either at all, or the signal periodically “fell off”; the picture crumbled into cubes, and there was freezing of the image and sound. One of the digital television packages could disappear, while the other was working normally.

The problem with these phenomena is over-amplification of the signal.

There is a way out, let's consider the options...

1) Sometimes it’s just enough to unplug the antenna’s power supply from the outlet and that’s it. But this does not always help and then more serious measures are needed.

2) Reduce the amplifier supply voltage using an adjustable power supply. Or supply power directly from the set-top box, bypassing the separator of the standard antenna power supply, by installing a regular plug.

3) Get to the amplifier board, the board that is on the antenna itself, and connect everything without an amplifier.

4) Throw away this old dilapidated antenna and buy a normal UHF antenna.

P.S. New type grille.

I hope this article will be useful to someone, leave your reviews, comments, and share your experience.

P.S. If you are purchasing a new antenna, but are not sure whether it will suit you, ask your local antenna dealers.

Sometimes they are quite knowledgeable about which antenna is best to take based on your place of residence.

And agree on the possibility, if it suddenly doesn’t work, to change it to a different type of antenna. At least in my store this is possible.

Buying a good antenna for your dacha is not always advisable. Especially if she is visited from time to time. The point is not so much the cost, but the fact that after a while it may not be there. Therefore, many people prefer to make an antenna for their dacha themselves. Costs are minimal, quality is good. And the most important point is that a TV antenna can be made with your own hands in half an hour or an hour and then, if necessary, can be easily repeated...

Digital television in the 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, the picture is of good quality. Due to this. Any decimeter antenna is suitable for receiving digital television. Many radio amateurs are familiar with the TV antenna, which is called “zigzag” or “figure eight”. This DIY TV antenna can be assembled literally in 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 and is easy to bend.

It is very simple to make; the material is any conductive metal: tube, rod, wire, strip, corner. Despite its simplicity, she accepts it well. It looks like two squares (rhombuses) connected to each other. In the original, there is a reflector behind the square for more reliable signal reception. But it is more needed for analog signals. To receive digital television, you can do without it or install it later if the reception is too weak.

Materials

Copper or aluminum wire with a diameter of 2-5 mm is optimal for this homemade TV antenna. In this case, everything can be done in literally 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 to the desired shape. The wire can be bent with a hammer, securing it in a vice.

You will also need a coaxial antenna cable of the required length, a plug suitable for the connector on your TV, and 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 are making a TV antenna with your own hands for installation on the street, pay attention to the quality of the insulation.

The mounting depends on where you are going to hang your homemade antenna for digital television. On the upper floors, you can try to use it as a home decoration and hang it on curtains. Then you need large pins. At the dacha or if you take a homemade TV antenna to the roof, you will need to attach it to a pole. For this case, look for suitable fasteners. To work, you will also need a soldering iron, sandpaper and/or file, and a needle file.

Is a calculation necessary?

To receive a digital signal, there is no need to count the wavelength. It is simply advisable to make the antenna more broadband in order to receive as many signals as possible. To do this, some changes were made to the original design (pictured above) (further in the text).

If you wish, you can make a calculation. To do this, you need to find out what wavelength the signal is broadcast on, divide by 4 and get the required side of the square. To obtain the required distance between the two parts of the antenna, make the outer sides of the diamonds slightly longer and the inner ones shorter.

Drawing of a figure-of-eight antenna for receiving digital TV

• The length of the “inner” side of the rectangle (B2) is 13 cm,
• “external” (B1) - 14 cm.

Due to the difference in lengths, a distance is formed between the squares (they should not be connected). The two extreme sections are made 1 cm longer so that you can fold the loop to which the coaxial antenna cable is soldered.

Making a frame

If you count all the lengths, you get 112 cm. Cut off the wire or whatever material you have, take pliers and a ruler, and start bending. The angles should be 90° or so. You can make a little mistake with the lengths of the sides - 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 each.
• Two 13 cm each, but with a turn in the opposite direction - this is the point of inflection onto the second square.
• Again two 14 cm each.
• The last one is 13 cm + 1 cm per loop.

The antenna frame itself is ready. If everything was done correctly, there will be a distance of 1.5-2 cm between the two halves in the middle. There may be small discrepancies. Next, we clean the loops and the bend point to bare metal (treat it with fine-grain sandpaper), and tin it. Connect the two loops and crimp them with pliers to hold them tightly.

Cable preparation

We take the antenna cable and carefully clean it. How to do this is shown in the step-by-step photo. The cable must be stripped on both sides. One edge will be attached to the antenna. Here we strip it so that the wire sticks out 2 cm. If it turns out more, the excess (later) can be cut off. Twist the screen (foil) and braid into a bundle. It turned out to be two conductors. One is the central monocore of the cable, the second is twisted from many braided wires. Both are needed and need to be tinned.

We solder the plug to the second edge. A length of 1 cm or so is sufficient here. Also form two conductors and tin them.

Wipe the plug in the places where we will solder with alcohol or solvent, and clean it with emery (you can use a needle file). Place the plastic part of the plug on the cable, now you can start soldering. We solder a monocore to the central output of the plug, and a multicore twist to the side output. The last thing is to crimp the grip around the insulation.

Then you can simply screw on the plastic tip and fill it with glue or non-conductive sealant (this is important). While the glue/sealant has not hardened, quickly assemble the plug (screw on the plastic part) and remove the excess compound. So the plug will be almost eternal.

DIY DVB-T2 TV antenna: assembly

Now all that remains is to connect the cable and the frame. Since we were not tied to a specific channel, we will solder the cable to the middle point. This will increase the broadband 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 routed 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 solder joints with sealant. If the reception is poor, try first to find a place where the fishing is better. If there are no positive changes, you can try replacing the cable. To simplify the experiment, you can use regular telephone noodles. It costs a penny. Solder the plug and frame to it. Try it with her. If it catches better, it’s a bad cable. In principle, you can work on “noodles”, but not for long - they will quickly become unusable. It is better, of course, to install 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 method is unreliable. If you remember, you can put on several heat-shrinkable tubes before soldering to insulate them. But the most reliable way is to fill everything with glue or sealant (they should not conduct current). As a “case” you can use lids for 5-6 liter water cylinders, ordinary plastic lids for jars, etc. We make indentations in the right places - so that the frame “sits” in them, do not forget about the cable outlet. Fill it with a sealing compound and wait until it sets. That's it, your DIY TV antenna for receiving digital television is ready.

Homemade double and triple square antenna

This is a narrowband antenna, which is used if 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 precise orientation to the source. The same design can be made to receive digital television.

You can also make five frames - for a more confident reception
It is not advisable to paint or varnish - reception deteriorates. This is only possible in close proximity to the transmitter

The advantages of this design are that reception will be reliable even at a considerable distance from the repeater. You just need to specifically find out the broadcast frequency, maintain the dimensions of the frames and the matching device.

Construction and materials

It is made from tubes or wire:

• 1-5 TV channel MV range - tubes (copper, brass, aluminum) with a diameter of 10-20 mm;
• 6-12 TV channel 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 higher gain. The third, smallest square is called the director.

The upper boom connects the middle of the frames and can be made of metal. The lower one is made of insulating material (textolite, gettinax, wooden plank). The frames must be installed so that their centers (the points of intersection of the diagonals) are on the same straight line. And this straight line should be directed towards the transmitter.

The active frame - the vibrator - has an open circuit. Its ends are screwed to a textolite plate measuring 30*60 mm. If the 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. At least the upper part of it. Moreover, the wooden part should start at a distance of at least 1.5 meters from the level of the antenna frames.

Dimensions

All dimensions for making this TV antenna with your own hands are given 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 larger - 50 mm. Other sizes are given in the tables.

Connecting an active frame (vibrator) via a short-circuited cable

Since the frame is a symmetrical device, and it must be connected to an asymmetrical coaxial antenna cable, a matching device is required. 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 central conductor can be cut down to insulation, since it does not matter. The feeder is also cut. Here, too, the aluminum screen is removed and the braid is twisted into a bundle, but the central conductor remains.

Further assembly proceeds like this:

• The braid of the cable 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 cable (braid) is connected to the feeder braid using a rigid metal jumper (you can use wire, just make sure there is good contact with the braid). In addition to the electrical connection, it also sets the distance between 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 cable pieces must be parallel. The distance between them is about 50 mm (some deviations are possible). To fix the distance, clamps made of 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. Braid is connected to braid, center conductor to center conductor. To reduce the number of connections, the feeder and cable to the TV can be made single. Only in the place where the feeder should end must the insulation be removed so that the jumper can be installed.

This matching device allows you to get rid of noise, blurry contours, and a second blurry image. It is especially useful at a great distance from the transmitter, when the signal is clogged with interference.

Another variation 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, “testing” is carried out. The cable is connected to the TV, the central conductor and braid are moved up/down, achieving a better image. In the position where the picture will be clearest, the antenna cable branches are soldered, and the soldering points are insulated. The position can be any - from the bottom jumper to the transition point 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 television signal amplifier.

The simplest antenna for a summer residence is made 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. Cans must be metal. You can take aluminum beer beers, or you can take tin ones. The main condition is that the walls are smooth (not ribbed).

The jars are washed and dried. The end of the coaxial wire is cut - by twisting the braided strands and clearing the central core of insulation, two conductors are obtained. They are attached to banks. If you know how, you can solder it. No - take two small self-tapping screws with flat heads (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 through it, and screw it to the can. Just before this you need to clean the metal of the can by removing the deposits using fine-grain sandpaper.

The cans are secured to the bar. The distance between them is selected individually - according to the best picture. You shouldn’t 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 a way out in an emergency, this is an excellent option.

A simple Wi-Fi antenna made from a metal can

An antenna for receiving a Wi-Fi signal can also be made from improvised means - from a tin can. This DIY TV antenna can be assembled in half an hour. This is if you do everything slowly. The jar should be made of metal, with smooth walls. Tall and narrow canning jars work great. If you will be installing a homemade antenna on the street, find a jar with a plastic lid (as in the photo). The cable is an antenna, coaxial, with a resistance of 75 Ohms.

In addition to the can and cable, you will also need:

• RF-N connector;
• 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.

Wi-Fi transmitters operate at a frequency of 2.4 GHz 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 can 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 jar. It must be placed strictly at the desired point. Then the signal will be amplified several times. It depends on the diameter of the selected jar. All parameters are shown in the table. You measure the exact diameter of your can, find the right stitch, and have all the right dimensions.

D - diameter	Lower limit of attenuation	Upper limit of attenuation	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’s easier to position the emitter vertically upward, connect the cable going to the router or Wi-Fi card.

The era of digital signals has arrived. All broadcast television companies began to work in a new format. Analog TVs are reaching their end. They are still in working order and are found in almost every family.

In order for older models to successfully complete their service life, and for people to be able to use them when watching digital broadcasting, it is enough to connect the DVB-T set-top box to the TV receiver and pick up the TV wave signals with a special antenna.

Any home craftsman can not buy an antenna in a store, but make it with his own hands from available materials for watching digital TV programs at home or in the country. The two most accessible designs are described in this article.

A little theory

Operating principle of an antenna for digital packet television

Any television signal propagates in space from the emitters of the transmitting television tower to the TV antenna by an electromagnetic wave of a sinusoidal shape with a high frequency, measured in megahertz.

When an electromagnetic wave passes through the surface of the receiving beams of the antenna, a voltage V is induced in it. Each half-wave of a sinusoid forms a potential difference with its own sign.

Under the influence of an induced voltage applied to a closed receiving circuit of the input signal with resistance R, an electric current flows in the latter. It is amplified and processed by the digital TV circuit and output to the screen and speakers as image and sound.

For analog models of TV receivers, there is an intermediate link between the antenna and the TV - a DVB-T set-top box, which decodes digital information of an electromagnetic wave into a normal form.

Vertical and horizontal polarization of digital TV signal

In television broadcasting, state standards require electromagnetic waves to be emitted in only two planes:

1. horizontal.

In this way, transmitters send emitting signals.

And users simply need to rotate the receiving antenna in the desired plane to maximize the power potential.

Requirements for a digital packet television antenna

TV transmitters propagate their signal waves over short distances, limited by the line of sight from the top point of the TV tower emitter. Their range rarely exceeds 60 km.

For such distances, it is enough to provide a small power of the emitted TV signal. But, the strength of the electromagnetic wave at the end of the coverage area should form a normal voltage level at the receiving end.

A small potential difference, measured in fractions of a volt, is induced at the antenna. It creates currents with small amplitudes. This imposes high technical requirements on the installation and quality of manufacturing of all parts of digital reception devices.

The antenna design should be:

• manufactured carefully, with a good degree of accuracy, eliminating loss of electrical signal power;
• directed strictly along the axis of the electromagnetic wave coming from the transmitting center;
• oriented according to the type of polarization;
• protected from extraneous interference signals of the same frequency coming from any sources: generators, radio transmitters, electric motors and other similar devices.

How to find out the initial data for calculating an antenna

The main parameter influencing the quality of the received digital signal, as can be seen from the explanatory first figure, is the length of the electromagnetic wave of radiation. Under it, symmetrical arms of vibrators of various shapes are created, and the overall dimensions of the antenna are determined.

The wavelength λ in centimeters can be easily calculated using a simplified formula: λ=300/F. It is enough just to find the frequency of the received signal F in megahertz.

To do this, we will use a Google search and ask it for a list of regional TV communication points for our area.

As an example, a fragment of a data table for the Vitebsk region is shown with the transmitting center in Ushachi highlighted in red.

Its wave frequency is 626 megahertz, and its polarization type is horizontal. This data is quite sufficient.

We carry out the calculation: 300/626=0.48 m. This is the length of the electromagnetic wave for the antenna being created.

We divide it in half and get 24 cm - the desired half-wave length.

The tension reaches its maximum value in the middle of this section - 12 cm. It is also called amplitude. The whip antenna is made to this size. It is usually expressed by the formula λ/4, where λ is the electromagnetic wavelength.

The simplest TV antenna for digital television

It will require a piece of coaxial cable with a characteristic impedance of 75 Ohms and a plug for connecting the antenna. I managed to find a ready-made two-meter piece in the old stock.

I cut off the outer shell from the free end with a regular knife. I take the length with a small margin: when setting up, it’s always easier to bite off a small piece.

Then I remove the shielding layer from this section of the cable.

The work is done. All that remains is to insert the plug socket into the connector on the TV signal set-top box and direct the bare wire of the inner core across the incoming electromagnetic wave, taking into account horizontal polarization.

The antenna should be placed directly on the windowsill or secured to the glass, for example, with a piece of tape, or tied to the blinds mount. Reflected signals and interference can be shielded with a strip of foil located a short distance from the central core.

Such a design can be done in literally ten minutes and does not require any special material costs. It's worth trying. But, it is capable of working in an area of ​​reliable signal reception. My building is screened by a mountain and a multi-story building. The transmitting television tower is located at a distance of 25 km. Under these conditions, the digital electromagnetic wave is reflected many times and is poorly received. I had to look for another technical solution.

And for you on the topic of this design, I suggest you watch the video of the owner of Edokoff “How to make an antenna for digital TV”

Kharchenko antenna at 626 MHz

To receive analogue television signals of various wave frequencies, the design of a zigzag broadband antenna, which does not require complex manufacturing, worked well for me before.

I immediately remembered one of their effective varieties - the Kharchenko antenna. I decided to use its design for digital reception. I made the vibrators from a flat copper bar, but it’s quite possible to get by with round wire. This will make it easier to bend and straighten the ends.

How to determine the dimensions of a specific antenna

Online calculator

Kharchenko antenna (zigzag)

MHz

Let's use the all-knowing Google search. We write on the command line: “Calculation of the Kharchenko antenna” and press Enter.

We choose any site you like and perform online calculations. I went into the first one that opened. This is what he calculated for me.

I presented all his data with a picture indicating the size of the Kharchenko antenna.

Manufacturing of antenna design parts

I took the information provided as a basis, but did not accurately maintain all the dimensions. I know from previous practice that the antenna works well in the broadband wavelength range. Therefore, the dimensions of the parts were simply slightly increased. The half-wave of each harmonic of the sine wave of the electromagnetic TV signal will fit into the arm of each vibrator and will be received by it.

Based on the selected data, I made blanks for the antenna.

Vibrator design features

The connection of the ends of the figure eight busbar is created in the center at the bending stage. I soldered them with a soldering iron.

I created it according to the “Moment” principle, made it with my own hands from old transformers, and has been working for two decades. I even soldered 2.5 square copper wire with it in thirty-degree frost. Works with transistors and microcircuits without burning them out.

I plan to describe its design in a separate article on the website in the near future for those who also want to make it themselves. Follow publications, subscribe to notifications.

Connecting the antenna cable to the vibrator

I simply soldered the copper core and braid to the metal of the figure eight from different sides in its center.

The cable was tied to a copper bar, bent into a loop in the shape of a semi-square vibrator. This method matches the resistance of the cable and antenna.

Screening grid design

In fact, the Kharchenko antenna often works normally without signal shielding, but I decided to show its manufacture. For the base I took a wooden block. I did not paint or varnish: the structure will be used indoors.

In the back side of the block I drilled holes for attaching the screen wires and inserted them, and then wedged them.

The result was a screen for the Kharchenko antenna. In principle, it can be made of a different design: cut from a piece of frontal armor of a tank or cut from food foil - it will work approximately the same.

On the back side of the bar I secured the vibrator structure with a cable.

The antenna is ready. All that remains is to install it on a window to work in vertical polarization.

When a television receiver is located at a great distance from the transmitting generator, the power of its signal gradually weakens. It can be increased by special electronic devices - amplifiers.

You just need to clearly see the difference between the signals received by the antenna, which can be:

1. simply weakened;
2. contain high-frequency interference that distorts the shape of the digital sinusoid into the shape of some kind of “doodleball”.

In both cases, the amplifier will fulfill its role and increase the power. Moreover, the TV will clearly perceive and display a weakened signal, but with an amplified signal, playback problems will arise.

The waves are designed to eliminate such interference:

• high-pressure filters;
• screens.

They must be measured with an oscilloscope, and the methods of using various designs must be analyzed individually in each specific case. The antenna is not to blame here.