Progress is sweeping across the planet, but, unfortunately, not as fast as we would like. Therefore, at the present time, millions of TVs are not capable of receiving a digital signal without crutches, and the provider who cares about the convenience of the subscriber must give a TV signal, including in analog form.

State Plan for Disabling Analog Broadcast TV Channels

Although this is not fully relevant to the topic, but now it is simply impossible to ignore such a burning issue.

So: all these conversations relate exclusively to broadcasting. That is, the signal that spreads through the air from the nearest TV tower. Only for this signal in Russia is the state responsible, and only in it there will remain only two (in some regions, three) multiplexes. The analog component of cable broadcasting depends solely on the providers and most likely will not go anywhere. So if your TV is not connected to an antenna on the roof of a house or windowsill, then almost certainly this shutdown will not affect you. Why do I say “almost” and “most likely”? The fact is that some cable operators have already announced the impending termination of the provision of an analog signal to subscribers. It is difficult to understand motivation, because, as is clear from part 1 of my articles, it cannot bring substantial savings on equipment: only a few expansion boards in the general chassis are responsible for this. The release of carrier frequencies is also a dubious motivation: there is no need in the market for such a number of digital channels that can be put in place of disconnected analogue ones. Here, except that you can get hold of, selling consoles to subscribers, but we leave it on the conscience of the operators.
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Analog Signal Parameters

An analog television signal is the sum of three signals: amplitude modulated brightness, and frequency modulated color and sound (for SECAM used in the CIS). But to assess the quantity and quality, it is enough to take this signal as a whole, although we all observed more than once that with a terrible picture, the sound from the TV is good. This is due to better FM noise immunity. To measure the parameters of the analog signal in the device Deviser DS2400T provides the appropriate mode:



In this mode, you can use the buttons to switch the analog channels (the digital ones will be automatically skipped) like on a TV. Only instead of advertising and news, we will see something like this:



On it we can see the main parameters of the signal: this is the level in dBµV and the ratio of the signal level to noise (or more precisely, carrier / noise). Since the channels at different frequencies are subject to different phenomena during transmission, it is necessary to take measurements on several channels (at least at the two extreme ones in the frequency range).

In accordance with the requirements of GOST, the signal level at the input to the receiver should be in the range from 60 to 80 dB. In order to provide these values, the provider should give the subscriber at the connection point (as a rule, this is a low-voltage dashboard on the landing) ideally 70-75 dB. The fact is that anything can be happening on the subscriber’s territory: poor-quality or damaged cable, incorrectly chosen dividers, a TV with a bad sensitivity threshold. All this will ultimately lead to attenuation of the signal. But an excessively high signal level is also bad: a good TV with the right circuitry, including high-quality AGC, can handle the signal more than 100dB without serious consequences, but most low-cost TVs simply cannot cope with such a signal.

An indispensable companion of any signal is noise. It is brought in by active equipment at the stage of signal generation, then amplifiers amplify it along with the signal, and they add a little more from themselves. For an analog signal, this is very critical: all that snow, stripes and other distortions are the noise that needs to be measured and preferably, of course, reduced. To assess the quality of an analog signal, the ratio of the useful signal to noise is used, that is, the larger the value, the better. GOST determines the minimum value of 43 dB, in fact, the subscriber receives, of course, more, but for the same reasons as attenuation, this parameter may deteriorate on the way from the panel to the TV. Although it is believed that passive wiring can not make noise, but it can take over pickups from an electric cable laid alongside, for example, or take on a powerful on-air signal from a repeater. In addition, substandard or aged dividers can do their work - it is worth paying attention to.

In practice, the final image quality depends to a large extent on the TV itself. Of course, the analog signal does not have redundancy for noise protection, but filters in high-quality receivers, as well as built-in amplifiers are able to work wonders, but you shouldn’t hope for the provider.