On Sun, 13 Nov 2005 12:05:46 -0500, "Larry" wrote:

What am I missing here. Although my background is in electronics and
electrical engineering, I've specialized in power rather than communications
for thirty years. My scant and no doubt obsolete communications theory
always held that for great short-wave reception, double or even triple
conversion receivers were the norm. Now I see advertised, SW radios with
"... highly sensitive and selective latest state of the art single
conversion analog tuner circuitry....". What breakthrough has made single
conversion so state of the art?

Absolutle nothing, in fact single conversion sucks unless it is an up
conversion, and even then, mixer noise will wipe out reception above
about 10Mhz absent a good tuned RF amplifier in front. Of course
providing 3-5 Khz selectivity at 40Mhz tends to be a bit challenging.
Q on the order of 10,000......

Single Conversion with a 455khz IF strip doesn't have problems with
bandwidth, but image rejection in the SW bands sucks big time.