K3HVG wrote:
Bret, I can't fully agree with you on several points. The KWM and 75S
receivers are pretty good but so is the 51S1. The 75S-3B/C are arguable
better when tuned properly and in good electrical condition and in
consideration of the available filters. The problem with SWLing, so to
speak, is that although movable (read: re-tunable) throughout the HF
spectrum, both the KWM and the 75S receivers require an "internal"
retuning to maximize sensitivity when the excursion is made outside an
adjacent 200 kHz segment. You'll note in the manual a reference to a
"field alignment". This is required when shifting a noteworthy amount.
The KWM and 75S have limited re-tuning ability via the front panel
(preselector). The 51S1, on the other hand, has a fully tracked tuning
system throughout the HF spectrum. Price aside, and given a choice of
the two types of receivers, the 51S1 would wins hands down, in my mind,
as an SWL receiver. Frankly, though, I'd prefer and in fact use, among
others, R-390As or a Drake R4C (or "B") and an S&S DVFO-II. But, that's
why there are Fords, Chevys, and Toyotas.



I'd read the 51S was pretty broad on the front end, so much so that
selectivity from signals at various points was pretty low. I have
never seen one,actually. I have seen LOTS of KWMs and 75S-3s.

What advantage do purpose built VFOs have over generators like the HP
8656B, which can be had cheap if you will accept the rear-connector
versions? (I don't know why you can't just drill a couple of holes in
the front panel and put BNCs on and make up a couple of new cables
internally, for the huge difference in price, either, but that's
another story.)