In article , craigm
wrote:

Michael Black wrote:

HFguy ) writes:
Joe Analssandrini wrote:
John Plimmer wrote:

There was also a long thread on this newsgroup that claimed the
AOR 7030 had the best sync detector in the business, but I still
punt the R8B as the 7030 sync was NOT sideband selectable, which
is required for most good listening.

Dear John,

Contrary to what you write, the AR7030's synchronous detection
circuit IS most definitely sideband-selectable and features
double-sideband detection as well (so does the Drake R8B). It
does not feature a "fixed" sideband selection as does the Drake
R8B (or the Drake SW8/Grundig Satellit 800), but rather a
"variable" one using the passband tuning. (You can tune the
circuit this way as well on the Drake.)

If your description (above) is technically accurate, the 7030 does
not have a 'real' sideband sync' detector because it requires
using the passband tuning to select the desired sideband in the
double-sideband mode. The sideband sync' detector on the R8B uses
phase cancellation for rejecting the unwanted sideband. This is a
more effective rejection method than using only passband tuning.

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.

So, to say one is better than the other is challenging. If you wish
to say one is better than th other, you will need to describe the two
specific implementations in great detail. This must include the
characteristics of the filters and phasing networks over the range of
interest. Deetailed measurements of unwanted sideband rejection vs.
frequency would be good to see.

Like any functional feature in a receiver the effectiveness varies
depending on the reception situation. Sometimes shifting the passband
or selecting the sideband works best. The Drake just has another tool
that the AOR 7030+ does not have and sometimes it make a big difference
other times not.

--
Telamon
Ventura, California