[CQ-Contest] Re: [TowerTalk] Stubs and rx noise

[Jim Idelson]

Sylvan,

You should try disconnecting as many non-rf cables as possible from your 
radios. Essentially, you want to isolate the radios from all potential 
common-mode return paths. I recently started to experiment with this kind of 
noise reduction. I had found that noise levels didn't go down with the 
introduction of a variety of filters in the rf path. But, as I disconnected DC 
connections like the keyer cables, noises are reduced. This means there will be 
a need for lots of ferrites on those DC and control cables. Even the power line 
should be a suspect path.

Ground implementation is also going to have an impact on this kind of noise. 
Changing the way your equipment grounds are routed to the station single-point 
ground may have a positive effect. I recently made changes in grounding that 
resulted in a couple dB of improvement.

You will probably find that improvements are realized in small increments. 
There probably isn't one major source of coupling. You just have to gradually 
find a lot of paths and address them one at a time.

73,

Jim