Paul ) writes:
I just purchased a Hammarlund HQ-150 receiver for restoration and use
with a kit built synchronous-am detector to listen to medium and
shortwave broadcasts. By pure happenstance, it turns out that the
HQ-150 comes with an outboard unit made in the mid-1950s by Central
Electronics called a "Sideband Slicer". The "Slicer" appears to be,
among other things, some kind of unit for injecting a locally generated
and phased carrier signal into a received AM signal for improved
reception. Is anyone out there familiar with the Sideband Slicer and
how it's the same or different than today's synchronous-am detector
circuits?

- Paul

I don't know where you get that impression.

A "Sideband Slicer" is an adaptor for making an old receiver better able
to deal with SSB. So not only is it a product detector, but you get two
of them because it uses the phasing method to remove the unwanted sideband.
It's not as good as an IF filter to cut down on bandwidth, but it did help
when the receivers it was used with had AM-bandwidth selectivity, and
some RC and LC networks were cheaper than a mechanical filter.

It connects to the end of the IF strip of the receiver, and there is no
RF coming from the unit back to the receiver. I'm not sure how it hooks
up, but if there is an output it would be an audio signal so you can use
the receiver's audio output stage. There is no synchronization because
it's for sideband.

There were apparently two models, with the "B" model including a Q-Multiplier
for peaking or notching the incoming signal.

The scheme was first described in a ham publcation in 1951, and then various
companies offered up their own commercial versions. They date from a time
when there weren't receivers specifically designed for SSB, though as
that decade continued various manufacturers did start to produce receivers
with product detectors and better selectivity for SSB.

The phasing scheme is seen in some selectible sideband synchronous detectors,
but in both places it only offers a means of nulling out the undesired
sideband. The actual synchronous circuitry is elsewhere, and "Sideband
Slicers" and their siblings from other companies did not include such
circuitry since they were to improve SSB reception. Circa 1958, you did
see descriptions of synchronous detectors with selectible sideband (again
using the phasing method) in the ham magazines, but as far as I know nobody
produced a commercial version in the tube era.

Michael VE2BVW