RadioBanter - View Single Post

craigm · January 19th 07, 07:46 AM posted to rec.radio.shortwave

wrote:

If the selective fading is as tight as you indicate, then there would
be "holes" in the audio spectrum of the recovered AM, much like a comb
filter. Sync demod won't fix that problem.

Yes, with the right source material you can hear it. While a sync detector
can't recover content that isn't there, its strength is reducing the
distortion that is present when the carrier level drops below the
modulation. If you are recovering both sidebands, then the 'holes' will
probably not be at the same frequency and that would limit the effect.

There are too many people that think sync demod will cure everything.
It's just not true.

True, you need to understand what the sync detector does and what its
benefits are. If you have access to a radio with a good spectrum scope
(WinRadio G3 series) you can see selective fading real time.

Now if you have a nearby signal bleeding into the
desired signal, then pick the sideband the furthest away from the
interfering signal. Here, sync works great.

Other means are available to get similar results, although a working
sideband selectable sync detector works great

If you have fading, you can
narrow band the signal by using one sideband. It helps a bit, but the
signal will still fade.

If you are talking about fading of the entire signal, a sync detector is not
the solution.

All this assumes your sync is decent, and not a growler. Otherwise, all
bets are off.

A bad radio is another subject.