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Old June 6th 06, 07:00 AM posted to rec.radio.shortwave
Michael Black
 
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Default Sherwood SE-3 MK III D Synchronous High-Fidelity Phase-Locked AM Product Detector

craigm ) writes:

But are you arguing semantics, or outcome? Because the phasing method
of selectable sideband reception is not as good as the filter method.
A filter really knocks out the unwanted sideband, while the phasing
method tends to give far less rejection of the unwanted sideband.

Michael


Both methods have their limits to unwanted sideband rejection.

For the filtering method, no physical filter has infinitely steep sides, so
closer to carrier, the unwanted sideband rejection can be poor if you do
not want to also lose part of the desired sideband.

For the phasing method, the unwanted sideband rejection is based upon the
accuracy of the phasing network. The better the network, the better the
results.

But, when the phasing method was common, ie almost fifty years ago, they
were using a phasing network that would only be good enough. And I'm sure
when the method is used in the less expensive shortwave receivers of today,
it's for cost reasons (read simplicity and low parts count) rather than
to get improved performance.

Yes, in recent years people have done work on the phasing method that uses
more complicated phasing networks and which pay attention to detail, but
they are no longer simpler.

Note that I'm arguing the point because the poster I replied to seemed
to be comparing the two methods, and did say the phasing method offered
better unwanted sideband rejection, or at least that's the way I read it.

Michael