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