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#4
September 16th 06, 05:54 AM
posted to rec.radio.shortwave
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possible fix of rumble synch satellit 700
Mark Zenier ) writes:
In article , Telamon wrote: In article . com, wrote: Here is the article I found form newsgroup that mention about the way to eliminate the rumbling noise of synch detector . I hope someone can study it and give a conclusion on the improvement made be these modification. Snip Some radio stations are off frequency. Use a mode that injects a fixed receiver local oscillator frequency like CW mode to zero beat the receiver to the target signal then switch back to sync AM. And, from a dimly remembered article in QEX many years back, a lot of shortwave broadcast transmitters have a lot of phase noise. (Speculation: probably those high effiency transistorized class D ones). Put a noisy carrier into the servo loop, and the output of the phase detector will need just the right filters to not carry that through to the VCO. Wouldn't that be the July 1993 QST article that described a synchronous detector? I know you've mentioned it before. I can't put my fingers on the issue, it's around somewhere, and the reprint in the Handbook leaves off a sidebar or two. And that sidebar had something about why the author didn't go to a phasing synchronous detector. He definitely said something about the phase noise of the receiver's synthesizer, and hence I figure he said something about the SW transmitters (though I don't recall that bit). Michael |
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