Tabletop antenna designs for receiving digital TV. Loop antenna made of pipe. Why you don't need to strive for an antenna with an amplifier

Nevertheless, especially for Moscow residents, we present 3 boundary graphs (Fig. 1) for receiving digital DVB-T2 packets (multiplexes).

All 3 graphs are built for 3 reception conditions:

1 – long-range reception (receiving antennas with a gain of 16-18 dB, “long-range” class);

2 – average reception (receiving antennas with a gain of 10-12 dB, class balcony antennas);

3 – close reception ( indoor antenna"Delta").

In all cases it is assumed that used or active antenna with a built-in mast amplifier, or an external low-noise mast amplifier (F=2 dB) is used. Of course, the use of more expensive “long-range” antennas will provide much better (reliable) reception even in all weather conditions and over many years of operation. The higher the price of the antenna, the more attractive it is appearance and greater durability in use.

Reduction cable length at presence of a mast amplifier(of any type) does not make any difference either to the quality of reception or to its “range”. At absence of a mast amplifier The length of the reduction cable (especially when working on 2 or more TVs) is already very important.

When using indoor antennas(Amplification = 6 dB) it is necessary to remember that the walls (and radio waves will certainly pass through the window opening or walls) have shielding (attenuation of radio waves). In the calculations, a radio shielding coefficient of 6 dB was assumed. In practice, it can reach 14...18 dB. In other words, this means that the actual range can be reduced by 2-3 times, depending on the installation location of the indoor antenna and the radio shielding factor of the walls.

Curve with Acceleration=0 dB corresponds to common active indoor foreign antennas (as a rule, they are powered by mains voltage ~220 V/50 Hz). Such antennas have zero gain (without a built-in amplifier), but are quite aesthetic in appearance.

For residents of the regions The figure below shows similar dependences of the reception range R 0 depending on the height of the receiving antenna h for different installation heights of transmitting antennas - N. The curves are plotted for “long-range” antennas with a radiated transmitter power of 4 kW at a frequency of 600 MHz.

If your real transmitter power P differs from 4 kW, then the calculation of the real reception range must be adjusted according to the formula:
It is useful to note that if the height of the receiving antenna is over 15 meters, then you can calculate the reception range R for a height of 15 m, and then recalculate according to the formula:

Thus, for a receiving antenna elevation height of 30 meters, the reception range increases by approximately 1.4 times (for example, from 48.3 km to 68.1 km).

In conclusion, here are a number of useful practical advice for digital DVB-T2 reception:

Tip 1
Currently, it makes no practical sense to install bulky MV antennas. Taking into account the emerging digital DVB-T2 broadcasting, it is more profitable to spend money on one single high-quality UHF antenna complete with a built-in or externally connected mast amplifier.

Tip 2
Choose a mast amplifier with gain 12-20 dB and minimum noise figure (no more than 3 dB). If you purchase a mast amplifier on the market, then take into account the fact that they are not specialists selling there. Therefore, without listening to their recommendations, try to choose an amplifier with the maximum current consumption (about 40-70 mA). A higher current consumption corresponds to a higher dynamic range(minimizing distortion).

Tip 3
Try to ensure that the mast on which the antenna is mounted is grounded. Preferably install a lightning protection device between the antenna and the mast amplifier. If the reception is carried out in a house where there is already provision for standard system lightning protection, then no additional system you won't need it.

Tip 4
Preferably choose an antenna with the highest possible gain. This criterion for the UHF range when receiving digital DVB-T2 signals is the main one. All other things being equal, choose an antenna with minimal wind load and weight.

Tip 5
Try to minimize the length of the drop cable (between the antenna and the first amplifier). Drop cable length is 5-10 meters for the majority practical applications is considered acceptable.

Tip 6
Comfortable use a mast amplifier with a supply voltage of 5 V instead of traditional 12 V or 24 V. A 5 V remote power source is present in almost every DVB-T2 receiver, which is very convenient, because no additional power supply required.

Tip 7
For normal readability of digital DVB-T2 packets, a signal level at the antenna output of 36 dBµV is sufficient. Mast amplifier serves only to compensate for losses in a reduction cable and a splitter for several TVs.

Tip 8
To increase reception range choose a receiving antenna With maximum possible gain and install it whenever possible, as high as possible relative to the Earth's surface. The mast amplifier should be located as close to the antenna as possible or immediately purchase an active antenna.

At the beginning, I would like to inform you that there are no “digital” antennas. Any will do UHF antenna, specifically for Sochi, operating in the range 32 and 53 frequency channels. If you live in a place where there is direct visibility to the Sochi television center, then an indoor antenna will do (do not choose an antenna with a built-in amplifier) ​​or even an antenna made from a piece of TV cable will suit you quite well, considering that the first multiplex broadcast on 32 channel goes with an excess level compared to the level of the second multiplex on channel 53, so we will tune our whip antenna to channel 53.

To do this, take a piece coaxial cable RG-6 60-70cm, one end is terminated with an F connector and an adapter for connecting to the antenna socket of the TV. At the other end, the central core of the cable is exposed. Based on the calculation that channel 53 is at a frequency of 730 MHz, which is approximately 41 cm, this means that we expose 41 cm of the central core (you can use half of this or even a quarter). Next, we fix our antenna directly on both sides with tape. back cover our TV, the antenna is ready!

Not all residents of Sochi live in direct visibility to the television center; the more difficult the reception conditions, the higher the gain an antenna will be required. I want to warn against the illiterate use of amplifiers TV signal, most good amplifier This good antenna, and if there is no signal from your antenna, then there is nothing to amplify. Moreover, the amplifier can also ruin what was in the antenna. The fact is that the whole city is covered with a network of towers cellular communications, and the G-2 standard uses the 900 MHz range, which easily penetrates the antenna amplifier, and leads to intermodulation distortion, which does not allow the DVB-T2 tuner to work normally, as a result of which the TV writes, “no signal.”

To avoid this, LTE filters are used, which cut out what is above 850 MHz. The first multiplex does not call special problems with its reception, as it is broadcast from many repeaters in the city: Moldovka, Ermolovka, Cossack Brod, Golitsyno, Kepsha, Kudepsta, Matsesta, Dagomys and a dozen in the Lazarevsky district.

The second multiplex can only be received from the television center of the Central District and the repeater of the village of Veseloye. To receive a signal remotely from the television center, it is necessary to use an antenna with a high gain of 16-18 dB and channel amplifier 53 television channel. I will say right away that the amplifier cannot be assembled under amateur conditions. But you can build an antenna tuned to TV channel 53.

The 25-element “wave channel” antenna consists of a four-element reflector, a loop vibrator, twenty directors and a traverse. The antenna elements are made of wire or tubes with a diameter of 4-5 mm; they are attached in any way to the supporting boom (crossbeam), which is made of a rectangular tube with a side of 20 mm. The gain of such an antenna reaches 17 dB, the opening angle of the main lobe of the radiation pattern in the horizontal and vertical planes is 28-30 degrees. When installing this antenna, it is necessary to provide the ability to adjust the antenna not only horizontally, but also vertically, because the envelope wave always comes from above and a couple of decibels, which can be gained in conditions of poor reception, will not hurt. Antenna amplifier, preferably channel (53 k) must be installed on the mast closer to the antenna. The antenna is matched with the descent cable using a half-wave U-shaped elbow.

p.s. My father wrote the article, especially for Sochintsy :)

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 big: you have many channels in digital quality, no monthly fee, with minimum 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 taking an inexpensive one, but new model, after reading reviews on online store websites. As a rule, any receiver works, but the antenna has great value. 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 a problem-free (and most importantly, stress-free) quality reception maximum quantity digital channels TV.

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 large number options for homemade antennas for T2: from beer cans, from antenna cable, converted Polish, 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. Good option and copper wire. 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 reception antennas.

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, the 6th floor, I didn’t check lower, but in 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 zone confident reception, 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 very easy to set up - just turn maximum level signal and quality on your tuner channels. 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% functional and better than at least half, or even more, of purchased antennas, where they save on everything and sell garbage for good money.

Digital signals are already known to everyone for a long time. All television organizations have switched to the new format. Analogue television devices have moved aside. But despite this, quite a few are in working condition and can last for more than one year. In order for outdated equipment to complete its allotted operational life, while still being able to view digital broadcasting, you will need to connect DVB-T to the TV receiver and catch wave signals with a zigzag antenna.

For those who want to save money family budget and at the same time get high-quality television broadcasting, you need to pay attention to the Kharchenko antenna for digital TV with your own hands.

This unique design is known long time, but found myself relatively recently.

Operating principle of an antenna for digital television

After radio communications appeared, the relevance of using an antenna device increased. Since the 60s of the twentieth century, the then recognizable engineer Kharchenko flaunted a design of 2 rhombuses. This device allowed him to catch US airwaves.

This double square from thick copper wire. The squares are connected through open corners; this is where the cable from the TV is connected. To increase directivity, a grid made of material capable of conducting current is mounted at the rear.

Perimeter of squares equal to length wave to which the reception is tuned. The diameter of the wire should be about 12 cm for broadcasting from 1 to 5 TV channels. The design turns out to be far from compact, in the case of assembly for radio communications and meter-wave TV with up to 12 channels.

To make the device lighter, 3 wires of a smaller cross-section were used. Despite this, the size and weight remained impressive.

The antenna in question received its second wind when broadcasting in the UHF range. Most people are familiar with rhombuses, triangles and other homemade figures in the form of antenna devices for receiving a signal of decimeter waves. Antennas of this type can be found on balconies and windows of both private houses and multi-storey buildings.

At the beginning of the 2000s, American professor Trevor Marshall came up with a proposal to use this design in Bluetooth networks and Wi-Fi.

The biquad antenna is also an antenna device of a Soviet engineer. This option is created according to the same principles as a regular biquadrat. A distinctive feature is that at the tops of the squares, instead of the corners, there are additional squares.

As for the sizes of these squares, they are identical to the usual ones. This avoids additional calculations. It is enough to use the standard biquadrat calculation.

Let us remind you that the wires in the place where they intersect require insulation from each other.

Required materials and tools

Kharchenko's DIY television antenna for DVB T2 is quite economical. In order to assemble the structure, you will need the following parts:

• Wire;
• Coaxial cable;
• Wooden slats.

As for tools: pliers, hammer, sharp knife. If you plan to attach the antenna device to a wall or other surface, you will most likely need a drill for mounting.

Antenna calculation

Before you start creating the design, you will need to calculate the Kharchenko antenna. This will allow you to collect with maximum accuracy efficient device. Zigzag sizes DVB antennas T2 play a significant role in increasing signal reception.

Since technology has stepped forward, there is now no need to leaf through reference books or look for formulas for calculating dimensions. And even more so, carry out complex mathematical calculations in order to correctly develop a sketch or future drawing.

After this, you receive information: about the required length of the copper wire, its sides, and diameter.

Assembly of Kharchenko antenna for digital TV

Step-by-step instructions that will allow you to quickly assemble a Kharchenko antenna with your own hands for digital television:

1. Determine the polarization and frequency of the wave. The device must be linear.
2. The biquad type zigzag antenna device is made of copper. All elements are located at the corners, with one of them touching. For horizontal type polarization, the figure eight must stand upright. If you do vertical polarization, the structure lies on its side.

1. The side of the square is calculated using a special formula - wavelength, which is divided by four.
2. Imagine the design, it should be oval in shape, and pulled across the center larger side. The sides do not touch, but are in close proximity to each other.
3. We connect the antenna cable to the approach points on both sides. It will be necessary to block one direction of the diagram; for this, a fetal screen made of copper is mounted; it will be located at a distance of 0.175 from the working wavelength. It should be placed on the cable braid.

As for the reflector, previously it was made of textolite boards that were coated with copper. Today, this component is made from metal plates. It is on this principle that the design for receiving digital television is made. Nothing complicated. Everything you need is at hand.

Antenna testing

The device has been created, it’s time to check the effectiveness of the work done. To test the reception quality of the wave channel, you need to go to the receiver. Turn on the TV and receiver.

Open the main menu of the console, select automatic search channels. On average, this process will only take a few minutes. You can find channels manually, but to do this you will have to enter their frequency. To test Kharchenko’s design for a TV, it’s enough to simply evaluate the quality of the broadcast. If the channels show well, then the job was done correctly.

What to do if interference is visible? Rotate the TV antenna and see if the picture quality improves. Once the optimal location is determined, simply secure the device. Naturally, it should be directed towards the TV tower.

High-quality antennas have always been difficult to obtain - the Soviet industry practically did not produce them, so people made them themselves from improvised materials. Today the situation has practically not changed - in stores you can only find lightweight aluminum Chinese crafts that do not show good results and rarely live more than a year. What to do if you like to watch TV, but there is no quality reception? The answer is simple -Given free time and a pair of skillful hands, anyone can handle this.

Quite recently in Russia there was analog television, but now almost the entire country has switched to digital broadcasting. Its main difference is that it operates in the decimeter range.

You can create a homemade antenna for the digital range at home

This was done for reasons of economy and safety - maintenance of transmitting antenna-feeder stations is virtually not required, their maintenance is reduced to a minimum, and the harm from contact with powerful transmitters for masters is minimal. But similar stations have one serious drawback- low power. And if in a big city the signal can often be caught even on a piece of copper wire, then far from the transmitter, reception may be difficult. If you live outside the city, in remote areas or villages, you will have to assemble your own antenna and take it outside to catch the desired signal.

Attention:Signal problems can occur even in the city center. Decimeter waves are practically not dampened by other sources, but are reflected from thick reinforced concrete walls. In modern high-rise buildings there are many places where they are completely attenuated before reaching the TV receiver.

It is also worth noting that DVB-T2 (the new television standard) offers a fairly constant, but weak signal. When the noise level is one and a half to two units higher than normal, the TV reproduces the broadcast quite clearly, but as soon as the noise exceeds 2 dB, the signal disappears completely. Digital television is not sensitive to electromagnetic interference— it is not knocked down by a working refrigerator or microwave. But if a mismatch occurs anywhere in the system, the picture stops or falls apart. High qualitywill solve this problem, but in some cases it will have to be taken outside or onto the roof.

Basic requirements for antennas

The current television standards in the USSR are not suitable for modern realities— protective and directional coefficients today have virtually no effect on signals. The airwaves in cities are clogged and contain a lot of dirt, so you shouldn’t pay attention to these coefficients. You are guaranteed to get interference on any antennas, so there is no need to reduce the efficiency factor and efficiency factor. It is better to improve the antenna gain so that it receives a wide range of airwaves and selects the desired stream, rather than focusing on a specific signal. The processor of the set-top box or TV itself will isolate the necessary signals and create a normal picture.

So, Experienced engineers recommend building band antennas. They must be correctly calculated, receiving signals in a classical way, and not through engineering “optimizations” and traps. Ideal option— the device fully complies with theoretical calculations and geometry. Also, the constructed antenna must be consistent with the cable at operating ranges without the use of matching devices. In this case, it is best to create a frequency response that is smooth and even, since when the amplitude-frequency response dips or jumps, phase distortions appear.

Attention: analog Antennas with ferrite USS, which provide full reception of the old signal, practically do not work with DVB. You need to build a “digital” antenna.

In the article we will analyze modern types antennas working with new digital broadcasting.

Antenna types

DIY antennas for digital TV Can you assemble it at home? There are three most common options:

1. All-wave, or as radio amateurs call it, frequency-independent. It assembles very quickly, does not require high knowledge or specialized tools. Well suited for the private sector, villages, dacha cooperatives - where the airwaves are not clogged with garbage, but not too far from the transmitter.
2. Log-periodic range. It has a simple design and receives the signal well at close and medium distances from the transmitter. Can be used as a remote antenna if the transmitter is located far away, or as a home wall antenna.
3. Z-antenna and its variations. Many radio amateurs are familiar with meter-long “zeshki” - they are quite large and require a lot of effort to assemble. But in the decimeter range they are quite compact and do their job well.

Nuances of construction

If you want to build a quality antenna, you must master the art of soldering. You cannot twist the contacts and guides - during operation they oxidize, the signal is lost, and the picture quality deteriorates. Therefore, all connections are soldered.

You also need to deal with points of zero potential, where currents arise even in the absence of voltage. Experts recommend making them from a single piece of metal, without using welding at all. Even well-welded pieces can make noise at the boundary values, while a solid strip will “pull out” the signal.

Also when creating homemade antenna for digital TV you need to figure out how to solder cables. Today, copper is practically not used for braiding, since it is expensive and quickly oxidizes. Modern braiding is made of steel, which is not afraid of corrosion, but it is very difficult to solder. It should not be overheated or squeezed. For connections, use 36-40 watt soldering irons, flux and light solders. Dip the winding well into the flux and apply solder - it takes up perfectly with this method of application.

All-wave antenna

The all-wave antenna has a fairly simple design. It consists of triangles, copper wire and wooden slats. You can study the design in more detail in the picture - it does not represent anything supernatural.

The thickness of the wire can be any, the distance between adjacent wires is 25-30 mm, the distance between the plates is no more than 10 mm. The design can be improved by eliminating plates and using PCB. It needs to be given the appropriate shape or simply remove the copper foil in the shape of a triangle.

The remaining proportions are standard - the height of the device must match the width, the plates diverge at right angles. Zero potential is on the extreme line home antenna for tv , just at the intersection of the cable with the vertical guide. To avoid loss of quality, the cable must be tied to it with a tie - this is enough for coordination. Such an antenna, hung outside or directed at a window, receives virtually the entire frequency range, but has a slight dip, so you need to set the correct angle when fixing the antenna.

By the way, this design can be modernized using ordinary aluminum beer and cola cans. The principle of its operation is as follows: as the shoulder span increases, the working band expands, although other indicators remain within the original limits. The Nadenenko dipole, often used in military developments, works on the same principle. Aluminum cans are ideal in shape and size, creating vibrator arms in the decimeter range.

You can create a simple can antenna by simply soldering two cans to a cable. This DIY indoor TV antenna Suitable for viewing channels at a short to medium distance from transmitters. There is no need to coordinate anything in this scheme, especially if the cable length is less than 2 meters.

You can complicate the design by assembling a full-fledged array from eight cans and using an amplifier from a regular Polish antenna. This design is perfect for hanging outdoors in areas remote from the transmitter. To enhance the signal, a metal mesh can be placed at the back of the structure.

Z antenna

Complex Z-antenna designs with multiple loops exist, but in most cases they are not needed. You can easily assemble a structure from ordinary copper wire 3 mm thick. If you don’t have one, then just buy a 3 mm single-core copper wire 120 mm long - this will be enough for your work. This design consists of two segments. We bend the wire according to this pattern:

1. The starting section is 14 centimeters long. Its edge is bent into a loop to connect with the last one (the loop is 1 cm, the total length of the first piece is 13 cm).
2. The second piece is bent at 90 degrees (it is better to bend it with pliers to maintain the angles). Its length is 14 cm.
3. The third piece is bent at 90 degrees parallel to the first, length 14 cm.
4. The fourth and fifth pieces are 13 cm each, the bend does not reach the loop by 2 cm.
5. The sixth and seventh pieces are 14 cm each, bent at 90 degrees.
6. Eighth - returns to the loop, length 14, 1 cm goes to a new loop.

Next, you need to thoroughly strip the two loops and solder them. The opposite corner is also cleaned. The cable contacts are soldered to them - one is central, the other is braided. There is no difference which contact to solder to.. It is advisable to insulate the soldered areas; for this you can use sealants or hot-melt adhesive. The ends of the cable are soldered to the plug and also insulated with cambric.

To avoid displacement of segments, the edges can be strengthened. To do this, take a regular plastic cap from a five-liter bottle, cut 4 slits in it so that the wire is recessed to the base. Cut the fifth hole for the cable. Then place the antenna in the cover (after checking the quality and reliability of the soldering), and fill it with hot-melt adhesive. The resulting design will be practically eternal - it is capable of receiving a stable signal at a distance of up to 10 km from the source.

So you already know What can be used instead of an antenna for a TV. In fact, the structures are much larger than those we described, but even these will be quite enough for you. If you live far from the signal source, then you will need amplifying antennas - you can get by with a classic “polka” with amplification. Well, if everything is bad with the airwaves, then use satellites.