Digital terrestrial television, how to set up an antenna under different signal conditions. UHF antenna for digital television DVB-T2: installation, configuration

If the development of terrestrial broadcast digital television will continue at this rate, then in the near future satellite television will die as a class. After all, the cost of equipment for its reception is disproportionately less, and anyone can make an antenna at home within 30 minutes, spending no more than 100 rubles on it.

After the article was published, I continued my experiments. And the reason for this was the very good reception rates TV signal. What prompted me to think that the signal level in my case is powerful enough to receive digital terrestrial television in DVB-T2 format, and most likely you can get by with a simpler antenna.

After visiting the official website of the Volgograd branch of the Russian Television and Radio Broadcasting Network, I found out that DVB-T2 broadcasting in Volgograd is carried out from two places. One is the well-known “Mamaev Kurgan”, where the TV and Radio Center is actually located, and the second is “Nagorny” (the village of Nagorny, in fact this is the Krasnoarmeysky district). The distance to the second transmitter in my case is only 5 km. This explains good quality signal, so you can get by with a simpler antenna.

I began to “dig” the Internet for the most simple antennas"pin" type. Which in practice look like an antenna connector with a piece of bent stripped of braid antenna cable.

Don't be surprised, but for this piece antenna wire With the connector, the digital television signal of the DVB-T2 standard is perfectly received. With 100% quality. I wrote about my reception conditions and the distance to the television center transmitter in the previous one. The antenna is working!

Here is the data on the signal reception quality of the first multiplex, the result is 100%:

The picture is similar at the second multiplex, the result is again 100%:

I post the photo in such a way that the receiver and the antenna inserted into it can be seen. So that no one thinks this is a joke. And here is a rear view of the antenna inserted into the receiver:

How to make an antenna for DVB-T2 reception

The antenna for receiving digital terrestrial television DVB-T2 is a UHF antenna. Therefore, when calculating its size, you should know for which broadcast channel we are making it. Unfortunately, there is no simple antenna that would receive all television channels equally well.

In my case, the first and second multiplex are broadcast on UHF channel 37 (average frequency 602.5 MHz) and 39 frequency channel decimeter range (average frequency 618.5 MHz), respectively. And in order for our antenna to satisfactorily receive the signal from both multiplexes, we will tune it to the average frequency of 610.5 MHz.

Determine the average wavelength. Wavelength = speed of light / frequency of TV channel, where the speed of light is 300 thousand km/sec; channel frequency – 610.5 MHz. Thus, wavelength = 300/610.5 = 0.491 m. To make the antenna, we need ¼ of the wavelength, i.e. 0.491/4 = 0.123 m.

Next, take a piece of cable. We disconnect the antenna connector on one side. We retreat about 2 cm from it and cut off the insulation along with the screen. We make the central conductor, together with the insulation, equal to a quarter of the wavelength that we need. For clarity, we use the figure below:

Let me remind you that the distance from my house to the Nagorny transmitter is approximately 5 km, the windows of the room (kitchen) where the antenna is located face the side of the panel house opposite from the TV tower. The antenna works great under these conditions. The signal level and quality of image and sound are not affected by the weather or time of day. The quality is always 100%.

As a digital television signal receiver I used (clearly visible in the photo) a DVB-T2 Supra SDT-92 digital TV receiver and an old POLAR37 CTV4015 TV.

Conclusions and reviews about the DVB-T2 antenna

I remembered an institute joke that “antenna theory” (and I had such a subject) is a science that adapts to practice. That is, a craftsman assembled an antenna from beer cans or gaskets from the cylinder head of an internal combustion engine and the pundits sat down to come up with laws and formulas to explain from a scientific point of view why this antenna works.

Digital television is a modern alternative to standard TV. With this technology, image quality becomes significantly better at the same cost. The essence of this technology is that the signals are a sequence digital combinations electrical impulses. Digital technologies provide new opportunities for transmitting and receiving data.

It has its advantages. For example, mobility. There is no longer any need to run wires and cables; all you need is a TV, an antenna, a digital receiver and a power outlet. This autonomous system, which you can take with you, for example, to the dacha and watch TV programs with the same high-quality signal as in the city. In addition, on digital TV large number broadcast, and you can also access the Internet, TV guide, etc.

Possible causes of interference

A digital signal is generally reliable and much better than an analog signal, but even it is not immune to various types of interference. In any case, if the quality of the broadcast deteriorates, you will have to find out the reason why this happened. For example, if the TV does not show well and they are on, you need to check the antenna. Maybe it was installed poorly or just went wrong. The antenna can also break due to a large snowball or piece of ice. In addition, the TV may not show well due to a broken or faulty receiver, etc.

If, when connecting digital TV, the craftsmen fed the cable into the apartment, and further wiring was done independently (especially if there is more than one TV), then perhaps there is a bad tee. Interference may also occur if there is also a computer nearby and they are connected via HDMI cable. As a rule, interference on TV begins when the computer is turned on, and as soon as the computer is turned off, the image becomes high-quality again. In this case, interference may occur due to the computer (or rather, a video card with an HDMI port).

If you live on the top floor and the signal is weak, the nuts on the dividers may have oxidized or burned, the equipment has not been configured, or the optical receiver has failed. There can be many reasons for interference, and the easiest way would be to call a specialist to find it. the real reason and eliminated her.

Having digital television in your home makes it possible to watch a range of different digital television programs. Delivery of digital TV to the consumer is carried out by connecting to the appropriate cable television. At the same time, you can continue to watch analogue channels in full.

Instructions

You should know that to take digital signal you need to install equipment that has the function of receiving and playing on the TV screen the standards of the transmitted signal.

These may be the following devices.
Cable receiver, free-standing, DVB-C standard(when using cable networks) or DVB-T (when using regular broadcasting), having a separate control panel. The receiver should connect to the audio-video inputs of almost any TV, both analog and digital;
Modern TV, which has a built-in DVB-C and/or DVB-T tuner. IN in this case just a cable through which you receive the network signal to the antenna socket, and you can receive the signal after setting up the TV.
A computer, however, is required to view this additional availability PC card or external tuner connected via USB port.

do not use the one bought when your grandfather went to first grade;
don't buy the cheapest one with virtually no braid. Choose normal ones;
do not shorten as much as possible;
do not make sharp creases;
Do not roll the excess into a coil.

Even if you connect the pieces with a standard coaxial connector, the signal quality is guaranteed to deteriorate.

Using the amplifier

This inexpensive antenna for the garden gives good results. If you plan to receive only with this antenna, then its two long side “whiskers” can be unscrewed.

Wave channel

They give good results, especially for remote signal reception when it is quite weak.

Polish

Many TV viewers use the “Polish” antenna - a grid and four rows of antennae. It doesn’t matter where it was made, they used to call it “Polish”, and sometimes “mesh”. Very often she demonstrates not the best best characteristics to receive a digital signal.

In general, for reception at the dacha , very sensitive too. If the reception of the digital signal on it in your area turns out to be normal, then you are just lucky. The amplifier of this antenna can operate from a 5 Volt power supply, which can be taken from digital tuner, and then you do not need to use an additional power supply.

Zigzag

indoor antenna shows good results for . Even if you paid dearly for it, the result may be zero.

If you only want an indoor antenna as an on-air antenna for your dacha, you may be “advised” to buy it more expensive and “better”. But if you hope that she will start giving you a wonderful signal in your room, then this hope is in vain. If in the house bad signal, no antenna will help. External - this is the solution to the problem if there is no reception in the room.

Satellite

Remember? We're talking about ethereal, so forget about satellites. You won't be through satellite tuner accept terrestrial television in the DVB-T2 standard. You will not connect the T2 tuner to the . We receive the T2 signal from the nearest broadcast tower in the UHF range. To normal terrestrial antenna for the dacha, not a “plate”.

Previously, this article posted on the website “BELKA HOUSE. Let’s build a house ourselves” was called “Another advantage of a soft roof”, and was dedicated to an antenna that is well located under a roof that is transparent to radio waves and the distribution of antenna cable to televisions in a private or country house. However, with the passage of time associated with the introduction of digital terrestrial television (DTTV), much has changed, and the article itself has lost its relevance. Many questions have arisen related to mastering the reception of on-air digital multiplex packages. Why do some antennas work better than others, why is reception poor with active antennas, why over time? unstable signal and many more whys that have accumulated in the comments. However, some blog visitors independently coped with the difficulties of mastering the CETV reception, and I can only summarize them and my experience.

What needs to be done to receive terrestrial digital television?

You must have a TV with DVB standard– T 2 or for an old TV or TV with a different standard (DVB –T) purchase a digital receiving DVB set-top box–T 2.

Make sure that digital broadcasting exists in the region.

Reliable reception is commensurate with the distance to the television transmitter (TV tower), the height of its antenna and the power of the transmitter itself, as well as with the terrain. When using homemade 4-element antennas without an amplifier, at a distance of 80 km from Ostankino, in conditions of low terrain (lowland), the reception level at a height of 5 meters from the ground is 50% with 100% quality. Judging by the comments, similar distances using similar homemade antennas located at a height of 5 meters from the ground overlapped from the regional CETV transmission towers. With the same power of analog and digital transmitters, the digital signal travel range is higher.

What is meant by unstable ECTV reception?

Occasional freezing of the television picture, loss or stuttering of sound, scattering of the image in the form of a mosaic, or even a complete absence of the television picture. I encountered two reasons for unstable reception.

1. The simplest and most easily eliminated reason is a weak television signal level. Determining the signal level. There is an INFO button on the remote control for your TV or digital set-top box, and after 1–2 presses, all information about the signal parameters appears on the screen. Important parameters are signal level and quality, and when one of these values is less than 20%, reception is unstable. During the day, the level can vary within 10 - 15%, this is due to the conditions of the passage of radio waves and depends on changes in the troposphere and weather. But this is not the worst thing and the level itself can be increased by using an amplified antenna or raising it higher above ground level.

2. The reason is more complex and difficult to eliminate if the level or quality of the signal fluctuates and the most dangerous is when its fluctuations reach 0%. In this case, you won’t be able to wait for a television picture. This means that the level of external interference is commensurate with the signal level, and the difficulty itself lies in finding external interference. It can be emitted household appliance, closely spaced repeaters cellular communication or nearby radio broadcast transmitters, high voltage lines gears, etc. How to deal with this? Read on.

What antenna should be used when receiving terrestrial digital television?

If before receiving digital broadcasting the antenna received analog channels in the decimeter wavelength range, then it should also cope with receiving digital multiplex packages. So in the village I didn’t have to change anything and the combined antenna with amplifier (photo 3), located under the roof of the house, transparent to radio waves, successfully copes through a splitter (photo 4) with 4 televisions, some of which receive terrestrial digital channels.

Let me remind you once again that a roof made of soft roofing, slate or ondulin is almost transparent to radio waves and the parameters of the antenna under it do not change much, and at the same time it is protected from birds, precipitation: rain and snow, and therefore it is not afraid of corrosion. Its maintenance itself is also simplified.

Photo 5. At the dacha on weekends
this antenna doesn't work.

A similar antenna at the dacha (photo 5) lost digital channels on weekends (the signal or quality level twitched from 0% to 100%), and the reception of analogue programs was subject to severe interference. I dealt with the problem by using for each TV homemade antennas without amplifiers. In environments with strong interference, use antenna amplifier is impractical, since it will amplify all interference throughout the entire frequency range and overload the digital set-top box or TV.

I called the homemade antenna in photo 6 “Olympus 2014”, and it lived up to its name when this year at the dacha, an hour before the European Football Championship, it turned out to be better than the purchased Locus-Pro active antenna (photo 5). And in the Kaliningrad region, the “Polish” active antenna won, receiving better Polish and all Lithuanian channels.

What amplifier is needed to receive terrestrial digital television?

Antenna amplifiers that were previously used in antennas for analogue reception are not always suitable for ECTV reception and can fail in conditions of interference. When receiving a digital signal, the first place in the parameters of the amplifier will now be its linearity, the ability to pass a high-level signal without distortion. Next comes selectivity, the ability to suppress radio stations and interference outside the operating range. The signal to noise ratio is responsible for sensitivity, a value that determines the reception range, and the smaller this ratio, expressed in dB, the greater the range. But you shouldn’t get carried away with a high gain, since its high value will be inversely proportional to the linearity of the amplifier. The antenna amplifier must compensate for losses in the cable and in the splitter, if any. For every meter of coaxial cable in the UHF range, the loss is about 0.5 dB, and in a splitter, if there is one, about 10 dB. The antenna amplifier gain should be within 15 - 20 dB.

Why with cable? RCA“tulip” for the analog video input of the TV set-top box works stably, and with a cable HDMIAre not all multiplex packets received or does the signal level (quality) fluctuate?

Most likely, the HDMI cable is of poor quality, its shielding is missing, it is located next to the antenna and clogs it with interference. It is enough to lay the cable as far as possible from the antenna or position the antenna further from the cable. Pulse signals pass through the cable, which emit a wide range of higher harmonics into the air and their frequencies can fall into the bands of multiplex digital packages or into the intermediate frequency amplifier of a set-top box or TV, which causes reception failures.

Why is the transmitter several kilometers away, but the indoor antenna does not provide stable reception?

Sometimes it is enough to place the antenna behind a double-glazed window, since its transparency is not transparent to radio waves in all cases. Monitor, TV, digital set-top box, a charger or a power supply connected to the network, an active speaker, an HDMI cable and, finally, just a network cable emit interference in a wide range of frequencies, so the antenna should be located as far as possible from these radiation sources. 1.5 meters will be enough. For close distances, it is better to use indoor antennas without an amplifier, since the amplifier will increase interference from household appliances, and the reception will be unstable.

Interference can also be induced on the DVB-T 2 set-top box itself if it is poorly shielded or has a budget design. The case is almost comical when an active sound speaker located next to the console, possibly with pulse block power supply, its radiation interfered with the normal operation of the receiver.

How does a “digital” antenna differ from a decimeter antenna?

Antennas are no different - it's just a commercial move.

Why does a homemade antenna work better than a purchased antenna?

It's like a Stradivarius violin, made from the heart and for the people, it sounds better. Most likely, antenna developers do not pay enough attention to the production process, and for antenna manufacturers, these are just pieces of metal and wires where they can save on something. For example, a very cheap one is used coaxial cable with heavy losses. Once in my practice I came across an antenna housing that was simply a screen for radio waves; something was added to the plastic dye for beauty. And the use of active flux disables the antenna after a year, even if it was simply stored in a warehouse, wrapped in cellophane.

It all depends on the operating conditions. In the city and near the transmitting tower, it is quite possible to get by with a single-element antenna without an amplifier (photo 9). The farther from the tower, the higher the antenna should be from the ground, and the more O It must have greater amplification, that is, consist of more elements. The best results were obtained with a homemade Kharchenko antenna (photo 10).

Photo 10. Antenna "Kharchenko".

She covered the entire UHF range television broadcasting and therefore suitable for all regions Russian Federation, taking into account the fact that digital multiplex packages in different areas are widely scattered in terms of frequencies. In hilly areas, the Urals, the city of Yekaterinburg, the Kharchenko antenna covers a distance of 60 km. And in the area of Veliky Novgorod, its range at a height of 4 meters from the ground was 80 kilometers.

What to do if there are power lines nearby and digital reception absent?

Try using a spiral antenna with circular polarization, receiving the reflected signal from neighboring houses.

Why does a homemade antenna refuse to receive a multiplex packet at the center frequency of the range, but accepts the outer multiplex packets?

Again, it's all about interference. The antenna is tuned to the middle frequency and at this frequency it has better matching and gain, which means it is more susceptible to interference, which may be commensurate with the signal level, and the receiver will work unstable (the level or value of the signal quality will twitch). It is enough to find a place or position for the antenna to reduce the level of interference.

What to do if there are cell phone towers in the path of the television signal near the windows?

A homemade selective antenna amplifier with suppression of cellular communications at the edges of the range helped me. Repeaters mobile communications At frequencies 467 – 468 it is more difficult to suppress, since these frequencies are close to the operating range of digital television 480 MHz. You can try, blocking yourself from the repeaters with a reflector helical antenna, receive the reflected signal from houses on the opposite side. In this case, the level of interference from repeaters may be weaker than the useful signal, and reception will be stable.

Could the receiving set itself be the cause of the unstable signal?

Why not? Receivers are constantly being modernized, modified, and improved in order to reduce costs, and therefore the possibility of their failure cannot be ruled out. This year the following incident happened to me: a new budget DVB-T 2 receiving set-top box, model DENN DDT 103, deteriorated after three weeks of operation in the Russian climate with a temperature of + 30 degrees Celsius, and began to stutter and freeze after heavy rain. At first I decided that the homemade antenna had caught a cold. When the next day I swapped the consoles, I discovered a diseased budget option, in which up to 5 electrolytic capacitors were saved along the power circuits, and the remaining ones may have had “shrinked” capacity, which caused a voltage ripple incommensurate with life. Usually when high temperature Radio components are rapidly aging.

The operation to restore the set-top box took place in the field by adding a capacitor along the input power circuit large capacity(1000.0 µF), exceeding 10 times all installed ones. It is known that the larger the capacitance of the power filter capacitor, the less interference from pulse voltage converters that are used in the receiver power circuit.

After several years of good operation, one multiplex package disappeared.

The multiplex package has disappeared, the very first, main one, with Carousel and the Time program. I said a lot in the comments about this case, but trouble happened to me too. I turn on auto-tuning, the receiver stops at the frequency of the missing channel, tries to capture something, but nothing works. Receivers from different manufacturers do not receive signals, purchased and homemade antennas are silent. No, they even receive duplicate multiplex packets on other frequencies, from other transmission towers, but they regurgitate the first frequency of the main channel. Of course, I became interested in why there was duplication and unfolded the digital terrestrial television broadcast map.

Rice. 1.

It turned out that I was on the same radius of transmission towers (Ostankino, Butovo, Serpukhov), broadcasting on the same frequency of the missing multiplex channel. What is this - inconsistency frequency range, lack of synchronization or commissioning? For now, I just throw up my hands and repeat the phrase “time will tell.” All hope is for another transmission tower (in Chekhov), which will also stand in this line, but next to me.

Analogue wavelength antennas again flew into the sky with a span of several meters to watch the “Time” program through the snow falling on the screen and the walls of village houses were covered with satellite dishes.

And I, looking at the horizon, will wait while cutting down my antenna mast. After all, even on spaceships, in case the computers freeze, there is always a backup analog communication channel.

Perhaps the article will be supplemented.

Thanks to all blog visitors who contributed their comments to help compile this article.

Digital terrestrial DVB-T2 broadcasting is carried out in the UHF television range 470-862 MHz, divided into 48 channels of 8 MHz (21-69 channels). That's why in the settings digital receiver or TV, you need to select 8 MHz, 7 MHz is for countries with a different broadcasting standard, where the channel width is narrower.

Also in the settings you should select the channel number or the corresponding center frequency of the channel. Not to be confused with the image carrier frequency, this is for analog.

The UHF range has never been completely occupied by analogue channels, therefore (and not only), free channels used for transmission of digital multiplexes. On one TV channel with a width of 8 MHz you can transmit one analog channel or one digital multiplex with several digital channels. The fewer channels included in the multiplex, the higher their quality

It is in principle even easier to install and configure an antenna for receiving digital television than for analogue television, but you need to understand some simple things.

Indoor antennas are only for areas of reliable reception with a good location - a high point, direct visibility to the transmitter. Indoor active antennas may slightly improve reception if not in a good location. In other cases, they will simply be an element of the apartment’s interior.
For quality reception digital television it is necessary to use outdoor bands UHF antennas. The antenna itself has gain; the more elements in the antenna design (passive directors), the higher its gain. Two antennas of different designs at the same reception point will have different signal levels at the output.
At a greater distance from the transmitter, it would be more correct to use more powerful antennas, rather than active. I love it passive antenna You can make it active at any time by supplementing it with an antenna (mast) amplifier, and there is plenty to choose from.
Those who wish to gain more insight into the issues of choosing an antenna for digital television should read on the topics: “wave channel antenna”, “calculation of UHF antennas”
When choosing an antenna design, it is necessary to take into account the distance from the transmitter, and when installing the direction. Sometimes, if it is not possible to install the antenna on a direct signal, you can try to receive a reflected signal; with a reasonable approach, the result will always be positive. For mountainous areas, things are much more complicated.
If you are in an area where the transmitter has not yet been launched, you can try to receive a more distant signal. Here you need to experiment with more expensive antennas and amplifiers.
If the antenna has amplification, then the “wiring” elements are just the opposite - attenuation. All passive elements: cable, splitter, antenna sockets, connectors contribute their share of attenuation to the signal. In this case, it is necessary to remember that the signal received by the antenna will be greater than the signal supplied directly to the TV. To compensate for attenuation, amplifiers are used, but here you also need to remember that “a lot” of signal is also bad, over-amplification will occur.
Splitter is a divider than on more We divide the parts, the less each gets. If one apple is divided among three people, then each person will lose 2/3 of the apple. Antenna sockets are not only for beauty, but also for weakening the signal.
Any receiver, including the DVB-T2 receiver has sensitivity. Sensitivity is the signal level, from some minimum to some maximum value, with which the receiver can operate. All changes in signal level values that fall within this range do not affect the quality of the picture on the TV screen in any way(unlike analog TV). Anything less - weak signal (it is impossible to receive the entire multiplex), anything more - over-amplification(again, it is impossible to receive the entire multiplex).
The signal strength of multiplexes can be approximately estimated from neighboring or nearby analog channels. Each region has its own situation.

Actually the right approach this is to measure the signal level and calculate and/or control its attenuation.

If we take the 16th floor entrance as an example, then the main task there is not in receiving a digital television signal, but in its correct distribution throughout the home network. People encounter this same problem only in miniature in private houses and apartments when connecting several TVs.