[Elecraft] K2 - Strong Signal Interference

[Ron D' Eau Claire]

Dave, K7EL asked:


> His signal was thumping in all over the 20M band it seemed...
> Any thoughts on the best way to deal with a *very* strong
> adjacent signal on
> the K2?

I'd say that the first thing to do is to turn off the preamp if you are
using it and perhaps turn ON the Attenuator. I live in a fairly quiet area
and my K2 will seldom, if ever, lose any sensitivity by having the preamp
off and the attenuator on at 20 meters. I use the preamp at times on 10
meters, but that's just about the only band where my doublet antenna doesn't
provide more than enough signal for the K2 to hear all that it is capable of
hearing.

Checking to see if turning the preamp off or turning the attenuator on is
hurting the sensitivity is easy. Just tune to a clear spot on the band where
there are no signals, and then disconnect the antenna. If the background
noise drops, then the K2 is hearing all that it can possibly hear. Adding a
preamp or turning off the attenuator will do absolutely nothing to help it
hear a weak signal, but it will reduce the K2's ability to reject strong
local signals.

If the noise level drops when you disconnect the antenna, the sensitivity
will be entirely determined by the band noise. That's why more r-f gain in
the K2 won't help dig out a weak one. Of course, you want to do this on the
narrowest filter setting you might use since narrowing the bandwidth reduces
the band noise. That's why you can hear weak ones better with narrow filter
settings.

If the other station is still 'all over the band' with the attenuator on,
I'd listen carefully with a short, makeshift antenna that brings his signal
down to a mere S9 or so. You might find that he is STILL "all over the
band", meaning that he has key clicks or spurs or is making hash. In that
case, it may well be coming from his transmitter, not being created in your
receiver. I have heard a number of stations with more than one signal on the
band - one nice and clean and the other rough and unstable. And some of them
were halfway across the country. What's happening is that a stage is
oscillating or something else has gone wrong at the transmitter.

Unfortunately, too many Hams assume that if their rig is making r-f it is
working fine. They never check to see if it is transmitting a clean signal
unless someone knocks on their door. And even then they might take some
convincing <g>.


Ron AC7AC