T2 digital television is actively entering our lives. Today, many homes already have antennas installed to receive such a signal. But what about those who live in the suburbs or in a rented apartment? The solution is quite simple - this is a homemade antenna for T2, which can become an inexpensive and reliable alternative to a factory-made product.

DIY TV antennas

In order to catch digital terrestrial television, first of all, you need to have a supporting new digital format TV, and then you won’t have to buy a special set-top box.

In addition, an indoor or outdoor decimeter antenna is required. You should not believe those who say that the device must be digital or something else. You can simply make a TV antenna with your own hands from scrap materials, resulting in a powerful device that will perfectly receive the signal.

Simple do-it-yourself decimeter antenna

Before preparing materials for the manufacture of the device, it is necessary to calculate its future length. To do this, you need to find out the frequency at which digital broadcasting takes place and apply a special formula: divide 7500 by the frequency in Megahertz and round the result.

A decimeter TV antenna is made from a regular 75-ohm television coaxial cable and standard connector.

After all the correct actions have been carried out, the search for channels will begin. If the repeater is located in an area up to fifteen kilometers from the house, then the signal will be received well and an amplifier will not be required. If the distance is greater, then the use of an amplifier is necessary.

Do-it-yourself digital figure-of-eight antenna

In order to ensure that the signal quality is good, you can make a more complex homemade television antenna for TV.

To make it you will need to prepare:

• TV cable;
• a box;
• roulette;
• foil;
• glue;
• scotch.

The bottom of the box (for example, a shoe box) will need to be well coated with glue and completely covered with foil. In this case, it is necessary to ensure that the foil does not rise anywhere.

While the foil is sticking, you need to cut off two pieces of 50 centimeters each from the cable, and strip the ends of the insulation by carefully cutting off the outer sheath with a knife. Having bent the braid to the side at all ends, bend the segments into a circle so that they do not close completely. The distance between them should be approximately 1 centimeter.

Secure the resulting figure eight with tape to the lid of the box. In this case, you need to make sure that the stripped ends are located next to each other. The cable on the box should hold well, so there is no need to skimp on tape. The antenna frame is ready.

Now follows prepare the main cable, which will connect to the TV.

All that remains is to mount the connector for the TV. To do this, at the remaining end of the television cable you need to remove the insulation, squeeze out and cut off the braid, and remove the foil. Then, stepping back half a centimeter from the braid, remove the internal insulation of the core.

The television connector must be screwed onto the prepared cable so that the insulated core is not visible in the wide part. After this, from the edge of the connector you should retreat half a centimeter and bite off the excess part of the core, insert the second part of the connector and screw it on.

The cable and antenna are ready. Having installed the device in a convenient place, you need to point it towards the TV transmitter, connect the cable and turn on the TV. The antenna should work well and the TV should show no interference.

Homemade antenna made from cans

An antenna that will catch not one or two channels, but as many as seven or eight can be made from the simplest tin cans. To make it you will need to prepare:

First of all you should prepare the cable, removing the top layer from it at a distance of 10 centimeters from the beginning. The wiring inside the cable must be unraveled, the foil removed from under it, and one centimeter of the stripped layer cut off. You need to put a plug on the other end of the wire.

Now follows prepare the jars. Attach the cable core to the rings of one of them, and part of the unraveled wires to the other. If there are no rings, then you can screw self-tapping screws into the cans and wrap wires around them, treating the surface with a soldering iron.

After this, the jars need to be used with adhesive tape. attach to hanger. The distance between them should be 75 millimeters, the cans should be placed in one straight line.

The homemade television antenna is ready. Now you need to connect it to the TV using a plug and find a place for it where the signal will be best received.

Indoor TV antenna “Rhombus”

This design is a diamond-shaped frame, can be manufactured quickly and easily, and receives digital television signals confidently and easily. For it you will need to prepare a copper or aluminum rod about 180 centimeters long.

There should be two diamonds. One will act as a reflector, and the second as a vibrator. The side of the frame should be approximately 14 centimeters, and the distance between them should be about 10 centimeters.

After the rhombus is made, between the two ends of the rod it is necessary to install a dielectric. Its size and shape can be arbitrary. The main thing is to ensure that the distance between the rods is about two centimeters.

Now the upper parts of the frames need to be connected, and a cable must be connected to the copper or brass petals attached to the antenna terminal.

If the repeater is located far away or the resulting device will pick up a weak signal quality, then it will be possible add amplifier. The result will be an active decimeter antenna for TV, which can be used not only in the city, but also in the country.

Of course, such devices for receiving a television signal will not have an elegant design, but with their help you can enjoy your favorite programs.

In the days of huge tube TVs, a good antenna for high-quality analogue television reception was in short supply. Those that could be bought in stores were not of high quality. Therefore, people made UHF television antennas with their own hands. Today, many are interested in homemade devices. And even when digital technologies are everywhere, this interest does not fade.

Digital era

This era also affected television. Today T2 broadcasting is developing especially widely. It has its own characteristics. In those places where the signal level is slightly higher than the interference, fairly high-quality reception is obtained. There is simply no further signal. A digital signal does not care about interference, however, in a situation where there is a cable mismatch or various phase distortions almost anywhere in the transmitting or receiving path, the picture can appear in squares even with a strong signal level.

There have been other changes in modern television. Thus, all broadcasting is carried out in the UHF range, the transmitters have good coverage. The conditions under which radio waves travel through cities have changed greatly.

Antenna parameters

Before starting manufacturing, you need to determine some parameters of these structures. They, of course, require in-depth knowledge in various fields of mathematics, as well as the laws of electrodynamics.

So, the gain is the ratio of the power at the input of the reference system to the power at the input of the antenna used. All this will work if each of the antennas creates values ​​of intensity and flux density with the same parameters. The value of this coefficient is dimensionless.

Directional coefficient is the ratio of the field strength created by the antenna to the field strength in any direction.

It is necessary to remember that parameters such as KU and LPC are not interrelated. There is a UHF antenna for digital TV, which has a very high directivity. However, its gain is small. These structures are directed into the distance. Highly directional designs also exist. Here it comes in combination with a very powerful gain level.

Today you don’t have to look for formulas, but use special programs. They already take into account all the necessary parameters. All you have to do is enter some conditions - and you will receive a complete calculation of the UHF antenna, so that you can then assemble it.

Manufacturing nuances

Any structural element in which signal currents flow must be connected using a soldering iron or welding machine. Such a node, if it is located in the open air, suffers from contact failure. As a result, various antenna parameters and reception levels can become significantly worse.

This is especially true for points with zero potentials. According to experts, voltage can be observed in them, as well as current antinodes. To be more precise, this is the maximum current value. Is it available at zero voltages? No wonder.

Such places are best made of solid metal. Creeping currents are unlikely to affect the picture if the connections are made by welding. However, due to their presence, the signal may disappear.

How and what to solder with?

It is not very easy to make a UHF antenna with your own hands. This involves working with a soldering iron. Modern television cable manufacturers no longer make it copper. Now there is an inexpensive alloy that is resistant to corrosion. These materials are difficult to solder. And if you heat them long enough, there is a risk of burning out the cable.

Experts recommend using low-power soldering irons, low-melting solders, and fluxes. Don't skimp on paste when soldering. Solder will lie correctly only if it is under a layer of boiling flux.

Catching T2

In order to enjoy digital television, it is enough to purchase a special tuner. But it does not have a built-in antenna. And those that are offered as digital specials are too expensive and pointless.

Now we will learn how to catch T2 on a completely homemade design. A homemade UHF antenna is simple, cheap, and of high quality. Try it yourself.

The simplest antenna

To assemble this structure, you don’t even need to go to the store. To make it, a regular antenna cable is enough. You need 530 mm of wire for the ring and 175 mm from which the loop will be made.

The TV antenna itself is a ring of cable. The ends need to be stripped and then connected to the loop. And to the latter you need to solder a cable that connects to the T2 tuner. So, on the ring, the screen and the central core are connected to the loop screens. At the latter, the central cores are also connected. And the cable to the tuner is soldered as standard to the screen and central core.

So we got a UHF antenna, made with our own hands. Its design turned out to be very cheap and practical. And it works no worse than expensive store-bought options. It needs to be fixed to plywood or plexiglass. Construction clamps are perfect for this.

"People's" antenna

This design is a disk made of aluminum. The outer diameter of the element should be 365 mm, and the inner diameter should be 170 mm. The disc should have a thickness of 1 mm. First you need to make a cut in the disk (10 mm wide). In the place where the cut was made, a printed circuit board made of PCB should be installed. It should be 1 mm thick.

The board must have holes for M3 screws. The board must be glued to the disk. Then you need to solder the cable leads to it. The central core should be soldered to one side of the disk, the screen to the other. As for quality, such a TV antenna will receive better with two disks, especially if it is located far from the television repeater.

Universal antenna

Nothing supernatural will be used to make this design. We will make it from various available materials. However, even though it is homemade, it will work perfectly in the entire decimeter range. So, this UHF antenna, quickly made with your own hands, is in no way inferior to store-bought, more expensive designs. It will be completely enough to take T2.

So, to assemble this structure, you will need empty cans of canned food or beer. You need 2 cans with a diameter of 7.5 cm. The length of each is 9.5 cm. You also need to stock up on strips of textolite or getinax, always with foil.

Our cans need to be connected to PCB strips using a soldering iron. The plate of this material that will connect the containers at the top should have a continuous coating of copper foil. The foil on the bottom plate should be cut. This is done for convenient cable connection.

It is necessary to assemble the structure in such a way that the total length is not less than 25 cm. This antenna (UHF range) is a broadband symmetrical vibrator. Due to its surface area, it has large gain factors.

If suddenly you cannot find suitable jars, then you can use containers with a smaller diameter. However, then the foil will have to be cut on the upper connecting plate as well.

"Beer" antenna

Do you like to drink beer? Don't throw away cans. You can make a good antenna out of them. To do this, you need to attach two beer cans to any dielectric material.

First you need to choose a suitable cable, and then bring it to mind. To do this, the cable must be stripped. You will see shielding foil. There will be a protective layer underneath. But under it you can directly observe the cable.

For our antenna, you need to strip the top layer of this wire by about 10 cm. The foil needs to be carefully twisted so that you end up with a branch. The protective layer for the central core needs to be stripped to 1 cm.

On the other side, you need to solder a plug for the TV onto the cable. If you were a cable network subscriber, then you don’t even have to purchase this part and cable separately.

Now about the cans. It is advisable to use 1 liter beer containers. However, good German beer in such cans is expensive, and domestic beer is not sold.

Banks must be uncorked very carefully. Then you need to empty the container of its contents, and then dry it well. Next, use a self-tapping screw to connect our screen on the cable and the can. You need to screw the central core to the second one.

For higher image quality, it is better to connect the containers and cable using a splice.

The cans must be secured to some kind of dielectric material. It is necessary to take into account that they should be located on the same straight line. The distance between them depends on the capacity. All this can only be determined empirically.

Zigzag

The UHF zigzag antenna has the simplest possible design. The part itself is broadband. Its design allows for various deviations from the original design parameters. In this case, its electrical parameters will be almost unchanged.

Its input impedance in a certain range depends on the size of the conductors that will form the basis of the fabric. There is a dependency here. The greater the width or thickness of the conductors, the better the antenna will be matched with the feeder. In general, any conductors can be used to make the fabric. Plates, tubes, corners, and much more are suitable for this.

In order to increase the directivity of such an antenna, it is permissible to use a flat screen that will act as a reflector. The latter will reflect high-frequency energy toward the antenna. Such screens are often quite large, and the phase depends mainly on the distance.

On the practical side, only in rare cases is a reflector made from a single sheet of metal. More often it is made in the form of conductors that are connected in the same plane. For design reasons, you should not make the screen too dense. The conductors from which the screen itself will be made are connected by welding or soldering to a metal frame.

This design is very simple to make. It works well in the UHF range. In the USSR it was a real folk and irreplaceable model. It is small in size, so it can be used as an indoor UHF antenna.

The material will be copper tubes or aluminum sheet. The side parts can be made of solid metal. They are often covered with a net or covered with a tin. If one of the above methods is used, then the structure must be soldered along the contour.

The cable must not be bent sharply. You can see how to carry out this element in the presented pictures.

It must be guided in such a way that it reaches the side corner, but does not go beyond the antenna or side square.

UHF indoor antenna

This design is designed for easy and reliable reception of digital television signals. It can be made easily and very quickly. To do this you will need an aluminum or copper rod. Its length should be up to 1800 mm. This antenna can also be used as an outdoor antenna.

The design is a diamond-shaped frame. There should be two of them. One acts as a vibrator, the second works as a reflector. To receive T2, we need the side of our rhombus to be approximately 140 mm, and the distance between them to be 100 mm.

After the frame is made and the structure becomes rigid, a dielectric is mounted between the two ends of our rod. It could be anything. The shape and size are completely unimportant. The distance between two points of the bars should be approximately 20 mm. The upper parts of our diamonds need to be connected.

The feeder can be made from cable. It must be connected to brass or copper petals, which should already be attached to the antenna terminal.

If the resulting design does not meet your expectations, for example, the reception quality is poor or the repeater is located far away, you can equip the antenna with an amplifier, and the result will be an active UHF antenna. It is used both in the city and in the country.

The simplest UHF loop antenna

This design resembles the number "zero". By the way, this is its gain factor. It is ideal for taking T2. This part can work better than the products offered in stores.

It is also called digital because it can be used to perfectly catch digital broadcasts. It is narrowband, which is a significant advantage. It operates on the principle of a selective valve, which means reliable protection against interference.

For assembly you will need a regular coaxial cable with a resistance of 75 Ohms, as well as a regular TV plug. Of all the options, it is better to choose a cable with a larger diameter. You can use a cardboard box or anything else as a stand.

We determine how long the frame will be using programs for calculating antenna parameters. The material for making the frame can be used the same as for the cable. By the way, for calculations you need to know the digital broadcasting frequencies in your city.

The central cable core is not needed in the frame design. The stripped wire is twisted together with the core and braid of the frame. Then this connection needs to be soldered.

The structure must be placed on a dielectric base. It's best to keep it away from your tuner. It is important that there is no voltage at the antenna input.

So, we found out how to make a UHF antenna with your own hands. As you can see, this is not such a difficult task. But now you can watch your favorite TV shows in digital quality. And this design is installed in the same way as a regular store one - on the roof. You can use screws or a bolted connection. It should be installed in a safe place so that during gusts of wind it does not fly off along with a piece of slate. It is advisable that the antenna be mounted at the highest possible height. This way you will avoid interference when showing cable or digital television.

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:

1. 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.
2. 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.
3. 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 flyer 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 homemade people can do is set up a satellite dish, about that.

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):

• 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:

1. If the antenna is a band antenna, the powers are calculated at the frequency of the useful signal.
2. 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.

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 works only 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.

Beer all-wave

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 “tavern” 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.

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.

Video: making a simple 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 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.

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, you can achieve 26 dB 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:

1. They start it, for the sake of frequency reserve, with the second longest vibrator.
2. Then, taking the reciprocal of the progression index, the longest dipole is calculated.
3. 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.

Antenna “Delta”

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.

The design of the MV Z-antenna is shown in Fig; The cable route is highlighted in red. There in the lower left there 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 band 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.

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

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 highly 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:

• 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 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 adjustment of the AVC is interdependent, and an amateur will certainly get confused.

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. Belt amplifiers are, firstly, low-noise, broadband. 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.

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.

(2 ratings, average: 4,00 out of 5)

said):

And on the roof there was a satisfactory reception for Polyachka. I’m 70–80 kilometers from the television center. These are the problems I have. From the balcony you can catch 3-4 pieces from 30 channels, and then with “cubes”. Sometimes I watch TV channels from the Internet on the computer in my room, but my wife cannot watch her favorite channels normally on her TV. Neighbors advise installing cable, but you have to pay for it every month, and I already pay for the Internet, and my pension is not flexible. We keep pulling and pulling and there’s not enough for everything.

Pyotr Kopitonenko said:

It’s not possible to install an antenna on the roof of the house; the neighbors swear that I walk around and break the roofing material covering and then their ceiling leaks. Actually, I am very “grateful” to that economist who received a prize for saving money. He came up with the idea of ​​removing the expensive gable roof from the houses and replacing it with a flat roof covered with poor roofing material. The economist received money for saving, and the people on the top floors now suffer all their lives. Water flows on their heads and on their beds. They change the roofing felt every year, but it becomes unusable within a season. In frosty weather, it cracks and rainwater and snow flow into the apartment, even if no one walks on the roof!!!

Sergey said:

Greetings!
Thanks for the article, who is the author (I don’t see the signature)?
The LPA works perfectly according to the above method, UHF channels 30 and 58. 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 before the shortest one has a significant effect, judging by the signal intensity in %. Especially in city conditions, where you need to catch (in my case) the reflected signal. Only I made an antenna with a “short circuit”, it turned out that way, there was simply no suitable insulator.
In general, I recommend it.

Vasily said:

IMHO: people looking for an antenna to receive digital TV, forget about the 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 on the shores of the Soviet Baltic states. In magazines of the time, this was bashfully called “extra-long-range reception.” Well, we really loved watching Swedish porn at night on the Riga seaside...

In terms of purpose, I can say the same about “double, triple, etc. squares”, as well as any “zigzags”.

Compared to a “wave channel” of similar range and gain, LPAs are more bulky and material-intensive. Calculating the LPA is complex, intricate and more like fortune telling and adjusting the results.

If in your region ECTV is broadcast on neighboring UHF channels (I have 37-38), then the best solution is to find a book online: Kapchinsky L.M. Television 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 et seq. (Fig. 39, Table 11).
If the transmitter is 15 - 30 km away, the antenna can be simplified by making it four - five element, simply without installing directors D, E and Zh.

For very close transmitters, I recommend indoor antennas; by the way, in the same book on pp. 106 – 109 there are drawings of wide-range indoor “wave channel” and LPA. The “wave channel” is visually smaller, simpler and sleeker with higher gain!

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Digital television T2 is gaining momentum in popularity. And this is natural, analogue television is being replaced by digital television and this is an irreversible process. Moreover, in the near future, analogue broadcasting will be stopped altogether. What should users who have TVs without a T2 receiver and no cable television do? The answer is simple - buy a T2 set-top box. Today, the price of T2 consoles has dropped greatly and does not look exorbitant. The advantages are quite large: you get many channels in digital quality, without a monthly fee, at minimal costs and without buying a new TV. Only by comparing the quality of digital and analog TV will you never regret your choice.

Quite a lot has been written on the choice of T2 receivers. Moreover, new models are constantly being released. I would advise you to take an inexpensive, but new model, after reading reviews on online store sites. As a rule, any receiver works, but the antenna is of great importance. Even if you are close to a TV tower, but are blocked by high-rise buildings, etc. - and this is almost always the case, then a good antenna is the key to problem-free (and most importantly, stress-free) high-quality reception of the maximum number of digital TV channels.

But an expensive antenna is not always a good antenna. Especially if you are 50 km or more away from the TV tower. Stores offer “special” antennas for T2. In fact, there is nothing “special”; you need a good antenna for the DCM range. If you still have an old DCM antenna, try connecting it first. Widespread "Polish" antennas are not suitable for receiving T2 digital channels.

I offer a proven option that is simple, but at the same time has proven itself, homemade antenna for T2. The shape of the antenna is not new; it has been used for a long time and when receiving DCM analog television, but the dimensions are optimized for receiving T2 digital channels.
It is worth noting that the Internet offers a large number of options for homemade antennas for T2: from beer cans, from the antenna cable itself, a converted Polish one, etc. This is for the completely lazy, and you shouldn’t expect quality from such antennas.

So. The long-known “figure eight” was taken as the shape of the antenna. The antenna body is made of any conductive material of suitable cross-section. This can be copper or aluminum wire with a thickness of 1 to 5 mm, a tube, strip, busbar, corner, profile. Copper is, of course, preferable. I used 6mm diameter copper tube. Copper wire is also a good option. I just had such a pipe.

Dimensions

The outer side of the square is 14 cm, the inner side is slightly smaller - 13 cm. Due to this, the middle of the two squares does not converge, leaving a gap of about 2 cm.
In total, you will need a tube, wire or other material 115 cm long (with a small margin).

The first section is 13 cm + 1 cm for a loop (for strength), if made of wire, or riveted for overlapping soldering for a tube. The second and third - 14 cm each, the fourth and fifth - 13 cm each, the sixth and seventh - 14 cm each, and the last eighth - 13 cm + 1 cm, again for connection.

We strip the ends by 1.5 - 2 cm, twist the two loops behind each other, and then solder the joint. This will be one cable connection pin. After 2 cm another.

From a copper tube it looks like this

It’s a little more difficult to bend the tube, but we don’t need much precision. Minor flaws in the shape do not affect the performance of the antenna. But the fact that the conductor area increases is a plus. Well, the conductivity of copper is higher than that of aluminum and, especially, steel. The higher the conductivity, the better the antenna reception.

The connection prepared for soldering is first riveted and cleaned. For soldering you need to use a powerful soldering iron (from 150 W). Simple amateur radio at 30 watts. don't solder. You can use acid for soldering.

Check the geometry again and solder the connection

If you are not particularly bothered by the aesthetic appearance, you can simply attach the antenna to a glazing bead or any other available holder. This antenna was located in the attic, so the simplest mounting method was used - electrical tape. If the antenna will be placed outdoors, take care of more aesthetic and reliable mounting.

This is a version of the T2 antenna made of aluminum wire with a diameter of 3 mm. Secure with one screw to the window. The distance to the TV tower is about 25 km. True, it’s the 6th floor, I didn’t check it below, but under these conditions the signal level is 100% and the quality is 100%. The cable is old, 12 meters to the TV. Receives all 32 channels. At first I was worried that it wasn’t copper, but as it turned out, it was in vain. Everything worked out perfectly on ordinary aluminum wire (which happened to be available). That is, if you have a reliable reception zone, then you don’t have to bother and feel free to use aluminum (I don’t know, maybe steel will do).

This antenna does not use any amplifiers. It is set up very simply - turn it according to the maximum signal level and quality on the channels of your tuner. Check other channels and fix the antenna. If reception is poor, you can experiment with not only rotating, but also changing location and height. Very often, the signal can be many times stronger if the antenna is shifted only 0.5-1 m to the side or in height. Good luck - the antenna has been tested - 100% operational and better than at least half, or even more, of purchased antennas, where they save on everything and sell garbage for good money.

Digital terrestrial television (DVB-Digital Video Broadcasting) is a technology for transmitting television images and sound using digital encoding of video and sound. Digital coding, unlike analogue, ensures signal delivery with minimal losses, since the signal is not affected by external interference. At the time of writing, 20 digital channels are available, and this number should increase in the future. This number of digital channels is not available in all regions; you can find out more precisely about the possibility of receiving digital channels on the website www.rtrs.rf. If your region has digital channels, then you just need to make sure that your TV supports DVB-T2 technology (this can be found in the documentation for the TV) or purchase a DVB-T2 set-top box and connect the antenna. The question arises - Which antenna should I use for digital television? or How to make an antenna for digital television? In this article I would like to dwell in more detail on antennas for watching digital television, and in particular I will show how to make your own antenna for digital television.

The first thing I would like to emphasize is that digital television does not require a specialized antenna; an analog antenna (the one you used previously to watch analog channels) is quite suitable. Moreover, only a television cable can be used as an antenna...

In my opinion, the simplest antenna for digital television is a television cable. Everything is extremely simple, take a coaxial cable, put an F connector and an adapter for connecting to a TV on one end, and at the other end the central core of the cable is exposed (a kind of whip antenna). All that remains is to decide how many centimeters to expose the central core, since the quality of reception of digital channels depends on this. To do this, you need to understand at what frequency digital channels broadcast in your region, to do this, go to the website www.rtrs.rf/when/ here on the map, find the tower closest to you and see at what frequency digital channels broadcast.

You will receive more detailed information if you click the "More details" button.

Now we need to calculate the wavelength. The formula is very simple:

where, λ (lamda) is the wavelength,

c - speed of light (3-10 8 m/s)

F - frequency in hertz

or simpler λ=300/F (MHz)

In my case, the frequency is 602 MHz and 610 MHz, for the calculation I will use the frequency of 602 MHz

Total: 300/ 602 ≈ 0.5 m = 50 cm.

Leaving half a meter of the central core of a coaxial cable is not beautiful and inconvenient, so I will leave half, or maybe a quarter, of the wavelength.

l=λ*k/2

where l is the length of the antenna (central core)

λ - wavelength (calculated earlier)

k - shortening factor, since the length of the entire cable will not be large, this value can be considered equal to 1.

As a result, l=50/2=25 cm.

From these calculations it turned out that for a frequency of 602 MHz I need to expose 25 cm of coaxial cable.

Here is the result of the work done

This is what the antenna looks like when installed.

View of the antenna when watching TV.