"Michael Black" wrote in message
...
Rick ) writes:
Well, I am beginning to have some doubts about the
likelihood of finding
an excellent-quality Hammarlund HQ-180 at a price I can
afford.

Certainly I am going to keep looking, but meanwhile I
guess I need to come
up with a few alternatives that I can "settle" for if, as
seems likely,
the HQ-180's have priced themselves out of my reach.

I need something that is all tubes, and works well on
SSB. I plan to use
it mostly on CW but I need decent SSB performance. AM is
relatively less
important (it should work on AM but doesn't need to be a
spectacular
performer).

It does need to be general coverage 500 KHz to 30 MHz.

R390's and 51J4's would be good (but of course, more
expensive than the
HQ-180) but none comes with a product detector and so
performance on SSB
is likely to be marginal at best, right?

This is mostly a myth. I had an SP-600 for years, and
never had problems
receiving SSB. You just turn down the RF gain, turn up
the audio gain
to compensate, turn on the BFO and tune away. The issues
of using
such receivers for SSB date from the very early days, when
people didn't
understand how to do it, and so they were disappointed.
Obviously, some
cheap receivers did have problems, because even with the
gain turned
way down, the BFO wasn't strong enough. But that's not
likely the case
for the better receivers.

The limitations would be in whether the dial allows for
fine enough
tuning (which will likely be fine in those receivers) or
lack of selectivity
(which won't be a factor with those receivers, and doesn't
actually affect
SSB reception, just affects how much other clutter you do
receive).

Having a product detector did make it easier to tune in
SSB signals, making
the process less cumbersome.

Michael VE2BVW

Many receivers without product detectors will do OK on
SSB but the problem is having to run at low RF gain and
having no AVC. My SP-600 does OK but I got better results
with my old BC-779 (SP-200 Super Pro) because the BFO
injection is isolated from the AVC and is greater. I don't
know why Hammarlund did not adapt this method to the SP-600
but it is only one of several puzzles about the design.
BTW, I have never understood the need for adjustable BFO
injection on most SP-600 models. The books suggest running
it at maximum but that results in tube overheating of the
buffer and some oscillator pulling. I set mine so that the
tube bias is "normal" for maximum amplification, 1 volt
measured at the cathode with the BFO off. The JXZ-17, which
has fixed injection, runs at this bias level.
There are many approaches to building an SSB adaptor. In
many cases they can be made to be plug-in with no
modification to the receiver. A great many designs were
published in QST and CQ magazines beginning in the mid 1950s
when SSB was becoming popular.


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Richard Knoppow
Los Angeles, CA, USA







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