Immediately we would point out that this article is not intended to be a comprehensive scientific research on anti-interference to TV reception. It attempts to summarize disparate materials in the many scattered around the Internet, published in magazines, publications, various reference books. Despite such a wealth of information to the ordinary viewer almost it is impossible to understand what is interference, why they hinder he watch your favorite programs, and what, in the end, you can to do for them, if not eliminate, then at least a significant reduction. Often articles on the subject abound scientific and professional terms, the design equations that complicate the understanding of the problem the person who just wants only "watch favorite football without interference". We have tried to outline the material is available in, "popular science" form, if possible avoiding professional difficulties.
In this article describes the organization of reception in specific conditions (far, chordally the TV reception, other "exotic" options) are General concepts and General recommendations that can be successfully applied in almost all cases.Let's start with terminology
The the signal that is transmitted to us by the telecentre, and which we wish to take into your TV, call the main. Signals that also carry the necessary information, but for different reasons either late, or come early primary, let's call retarded and faster. The signals are nothing but noise-not us bear, let's call noise. Signals, the sources of which are various kinds of nonlinear distortion in our TV set, let's call signal nonlinear distortion. The signals of neighboring telecentres, radio stations that we should not accept, but accept sometimes, let's call interfering."Know your enemy in face"
If you see on your screen a second image which is shifted to the left from the main one, know that you are taking leading signals! However, it is very rare, because leading signals appear as a result of reception of the main signal to your TV directly before this signal comes from the antenna to reduce cable. And since the cable length is decreasing in the individual reception in mostly small, almost time difference of arrival these two signals is not noticed.
Much more often on TV the second image appears shifted to the right from the main one. This means that our TV receives delayed signal, which came after the primary or due to multiple reflections from obstacles in its path from the TV tower to your antenna, either due to reflection between inconsistent the input on the TV and the antenna output (the signal is just "walked" on your cable reduction).
A different kind of "snow", "sparks", "stripes" and "dash" on the main the image, reducing its clarity, clicks and rumble sound say that are accepted noise interference.
Nonlinear interference will add to the screen grid moving vertical stripes.
Preventing interference "will give us the opportunity to" take their signal and sometimes you can even see the picture, to hear more often the soundtrack, or listen to the speakers of his the TV echoes of the radio.
All of the above is true, however don't forget that theory and practice don't always have one and also. In practice, rarely found separate interference, much often have to deal with their complex, that only complicates the task of dealing with them.
What can you do?
Let's start, perhaps, with the selection of components for our "antenna facilities".The antenna it is advisable to pick one that has a narrower directional pattern, to focus not on advertising statements of the seller, and on the specifications provided in the passport. It does not hurt to seek the advice and recommendation knowledgeable people. We must pay tribute, now in store professionally engaged in the sale of antennas, you really will provide the necessary consulting services for free. To believe this advice, as if antenna sold will not fit, you can always return while maintaining her presentation of the documents confirming the fact of purchase (the return policy is better to specify at the time of purchase from the seller to save your time and nerves). Pay attention to on the following parameters: gain, the ratio of protective action. Sometimes you may hear something like: KUS (KU), cpad. Don't worry, it's all the same! This is the reality - experts I love to insert in his speech accepted in their environment, of course) abbreviations and technical terms. Antenna with large values KUS and cpad have greater noise immunity, thus resulting in the quality of the received signal.
Antennas are sold as with cable, and without it. What to buy - you choose. Antenna with cable will ease installation, but not always, included is a high quality cable, and even the right for you length. To buy the cable separately now is not a problem. Better to stay on the version with double braid this cable has greater noise immunity. And not should pick up the cable solely from an aesthetic point of view! Not always something that looks beautiful, works well.
In any case, do not neglect the advice of those same professionals! Precondition: the cable has be consistent with the antenna output and input of your TV! If you want 75 Ohm, and should be 75 Ohms.
Now about all sorts of trendy outlets now. Remember the topic of the article? Now, if you have a difficult situation, we advise you not to getting involved with them. If you need it without them not to manage, purchase only high quality products, do not pursue cheap. Already "clogged" main the signal will get a low-quality outlet additional portion interference. The rule here is simple. The more on the path of the main signal connections and devices, the more likely it is to degrade!
Please note that all connections (cable to antenna, cable and combiner/splitter/sockets and etc.) in any event must be performed efficiently, providing reliable contact, not only immediately after Assembly, but in the future, in the process of operation.
With accessories briefly understood. Now on the place and method of installation of the antenna. Written by this issue very much, so we will give only brief information, without going into their scientific justification. A common misconception - the higher the better. Not always this is true. Sometimes better to put the antenna down, using as a shield on the path of the reflected signal to the Elevator superstructure for example, which is on your roof. Or move the antenna closer to the edge the roof towards the telecentre, then the surface is flat the roof for the antenna will reduce the parasitic effects of the trailing signals.
If you're reading this, then you are not an expert and you don't have the necessary measuring devices, so with the location the antenna on the roof (both horizontally and vertically) you will have to experiment. However, the task is not easy! In the city sometimes it is simply impossible to achieve good reception in a particular the antenna location. It is enough to shift for a few meters and high-quality picture on your TV will appear! And sometimes you have to install the antenna on a nearby house, throwing the cable on your home. In any case, try to organize high-quality reception of TV signals can and need! Any expert will not tell you with absolute assurance, in your case nothing can be done or everything is possible. To do now you can almost everything, though, and it can cost many times more expensive! It comes to use of various filters, attenuators, amplifiers, antenna arrays, finally. Not those lattices that in recent years flooded our market, and two designs or more antennas connected to a single receiving device. But this is a topic for another article, and to do, and most importantly - customize this design a layman are not able to.
Literature
Publication: antennaspb.ru, www.cxem.net