OIRT Tuner

Posted on Feb 6, 2014

For the long-distance listener (dx-er) it is a treat to listen on a band 8MHz wide which normally is completely empty, but which is capable of providing periods of clear reception during the `Sporadic E` season from several distant countries. Usually only one or two transmitters will occupy the band for a few tens of minutes, but when the ionisation

OIRT Tuner
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is widespread and intense the band can become jam-packed with pop stations, speech, news and cultural programmes for many hours It is interesting to note that, although the modulation details are the same as in the western CCIR FM band, occupying the same 200 - 250kHz of spectrum, the channel spacing is now 30kHz, rather than 100kHz. This is comparable to the `offsets` as used in TV channels to avoid co-channel interference. The pre-empahsis is 50kHz as in western Europe, and Zenith multiplex stereo is increasingly used, as well as the Soviet system in which the difference signal is transmitted as an AM reduced-subcarrier signal at 31. 25kHz. Tuners made for the band occasionally turn up on ebay. de, and there must be heaps of abandoned tuners in, say, Poland and Hungary. Locally produced PLL models were made by Diora in Poland and Teleton in Hungary. Several PLL synthesised models have been produced by Japanese manufacturers including Sony and Technics and generally offer manual switching between the two stereo systems. However, the `DX` community tends to use high-end `scanning` receivers or general-coverage VHF receivers, such as the Icom PCR-1000 or R7100 for this band. Alternatively, a dedicated receiver for the band can be made cheaply by modifying an old Band II FM tuner. The ideal model to choose would have both an FM `Tuning Meter` and Signal Level Meter, but the choice of tuner requires internal inspection of...

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