[Elecraft] RFI in audio chain

[Jim Brown]

Gee whiz -- I go into the hospital for a week and thing go WAY off the 
rails!  Thanks to W4TV and W3FPR for intelligently moving the discussion 
back on track.

Questions:

EXACTLY what is the configuration the the "vertical antenna? 
Quarter-wave with radials or half wave without radials?  How many 
radials?  How long?

Where is the antenna feedpoint with respect to the radio?  What coax are 
you feeding it with?  Are you SURE that the connectors at both ends are 
properly installed and gas-pliers tight at both ends?

Is there a short, fat copper bond from chassis to chassis between every 
piece of gear in your shack?  Is there short fat copper from there to 
all the other grounds in your home?

Joe is exactly right -- ANY "balun" that isn't multiple turns of coax 
around a #43 or #31 ferrite core is USELESS at HF.  Those "string of 
beads" "baluns" sold by various vendors are badly misguided copies of 
the W2DU design, which what a very good design that used a LOT of #73 
beads.

Joe is also exactly right -- the ONLY proper connection of a cable 
shield is to the SHIELDING ENCLOSURE of the equipment it feeds. The 
cable shield should ALSO be bonded to the shielding of the microphone.

Some fundamentals:  ANY antenna that "works" will put RF in the shack -- 
it does that by radiating RF. An antenna that lacks an effective common 
mode choke will ALSO put RF onto the feedline.

Summary of suggestions/comments:

Answer the questions I asked above.  They are all important.

Download and STUDY k9yc/com/RFI-Ham.pdf    and

http://k9yc.com/GroundingAndAudio.pdf

Follow these instructions carefully.  I suspect that the cause of Jan's 
problem is failure to properly connect cable shields, and/or to bond all 
the gear together.

73, Jim K9YC

On Tue,11/24/2015 6:54 AM, Joe Subich, W4TV wrote:
> Not true ... the Icom uses an electret mic, not the dynamic Audio-
> Technica.  If the microphone is wired correctly, the issue is in
> the antenna system and probably requires improved common mode
> decoupling.  Air wound solenoidal chokes are not sufficient in
> the most intractable cases *like elevated verticals*.
>
> Replace the elevated vertical with a dummy load.  If the RFI is
> eliminated, the problem is in the antenna system.