More on low pass filters

[Doug.Grant at analog.com]

A hint for you multi-transmitter fans...
 
At K1EA, there was a nagging problem with TS-940s on different bands talking
to each other. It was strange - the signal was perfectly tuned in, no matter
where the receiving radio was tuned. The culprit turned out to be leakage of
the 49MHz first IF out the antenna terminal - a few milliwatts is perfectly
audible through the reciprocal (receive) path. Any old lowpass filter kills
the problem - and it can be between the rig and amp, so it doesn't have to
handle a KW - it just has to have a lot of attenuation at 49 MHz or so. And
you only need it on one radio in a multi-2!
 
I had the same problem in my multi-2, and DIDN'T find the problem - K1EA
and KM3T get credit for the solution - my solution was to substitute a 930 for
one of the 940s - that worked, too...
 
K1DG