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?