Bret Ludwig wrote:
snip
I'm told that for specific 200 kHz swaths, a 75S or KWM is a much
better receiver than the 51S-1, which has a very promiscuous front end.


Hi,

I have an S/Line, KWM-2 and a 51S-1. The 51S-1 front end is fine
if it sees 50 Ohms. It has a double-tuned front end which is quite
selective when used with a proper antenna.
If you must use a random wire antenna with a 51S-1,
even an untuned preamp such as an E.F. Johnson electronic TR switch
will help the front end perform as designed.

Below 2 MHz, the 51S-1 is insensitive, and was intended to be used
with an external antenna tuner/ source follower for 50 Ohm input
to the receiver.

My only gripe against my 51S-1 is that the S/meter zero
drifts quite a bit, and I don't look forward
to chasing down a possibly leaky coupling capacitor
in the IF circuit.

73,
Ed Knobloch