SOTA TV transmitters
Leonid Chirkov

SOTA Chelyabinsk company has been manufacturing and developing TV transmitters of metric and decimetric wave bands, 1...12, 21...60 TV channels respectively for more than 10 years, since 1991. The transmitters are crystal-based. The decimetric transmitters series includes TV-1, 10, 100, 200, 500, 1000 W transmitters. The metric TV transmitters series includes TVM-1, 10, 100, 500, 1000 W transmitters, the transmitter with 200 W output power being excluded. It is important to note that all the transmitters are certified. By user option they may be equipped with a 100% stand-by. Automatic and manual modes of switching to the stand-by set are possible.

Mainly, all transmitter's units are designed on the most modern elemental base, unfortunately, of foreign production. At present, output amplifiers of DMV transmitters employ powerful Ericsson bipolar transistors, and MV transmitters use powerful Philips field transistors. In the near future DMV transmitters will use Philips field transistors too. Transmitters of 500 and 1000 W employ the most modern and reliable switched power supplies manufactured by the Emersson (former Ericsson) company.

Transmitter of SOTA Company

Along with the transmitters full documentation package (register, technical manual, service instruction, diagram and mark charts manuals) is supplied. SOTA transmitters are in quite high and firm demand in Russia, as well as in the CIS countries.

Ways of high-frequency signal formation are similar all over the world and SOTA transmitters are not an exception.

Transmitters have in their structure amplifier-modulator (including carrier frequency synthesizer, intermediate frequency synthesizer, CCTVS corrector, converter), preamplifier, output exciters, and high-frequency channel (including output filter, reflection meter, circulator and ballast load for output protection). Control systems are also provided. Output power, transistors current, output amplifiers' power, standing-wave ratio, overheating, video signal presence, and input signal level are under control.

Transmitter reliability much depends on reliability of its most power loaded units. These are power amplifiers and power supplies. The right choice of right active element and its load factor, as well as matched-load-operating and supply voltage stability are factors providing high reliability of transmitters. That is why we use Ericsson PTB20101 transistors, operating with 0,5 load factor, as an active element.

Mismatch load operating is provided by Y-circulators protecting amplifying stages' outputs under emergency conditions. Ballast load, included into the isolated circulator arm, is intended for continuous dissipation of reflected power sent at emergency condition loads, which also contributes to reliability improvement. Transmitters power exciters use switched power supplies of Ericsson manufacture. Small in dimension, these supplies are characterized by high performance factor and high power. According to the manufacture, average time of mean-time-between-failures of the supplies exceeds 60 years. Control and indication system quickly evaluates the transmitters' operation and detects a defective unit, if necessary.

By customer option, transmitters of 500 W and more may be equipped with built-in RF analyzer of RAP-TV parameters, developed by SOTA specialists. PC management allows controlling transmitter's parameters during broadcasting and maintenance.

Provided by SOTA Company.