[Elecraft] My KAT500 seems very sensitive to common mode RFI

[Michael Walker]

To re-enforce what has been said already, I read the Contest Clipper Club
report and then a few others, and to summarize, here is what I found:


   - I ordered a few dozen Mix 43 and Mix 31 chokes online.  I think I
   ordered 24 of each type and used the model numbers in the CCC document I
   quoted earlier.
   - I solved RF feedback issues (like bad SWR readings) but choking
   feedlines.  This was really apparent in the mobile when the screwdriver
   would never seem to resolve turning on 40m.  Once I choked the control line
   and the feedline, the antenna has never worked better.
   - Next was receiving.  I had to start choking things in the station and
   around the station.  I made good use the FT817 and the break panel to see
   what noises disappeared as I started to flip breakers in the house.

I'm a believer in the right choke for both receiving issues and
transmitting issues.  I also believe that it is even more critical than a
good ground.

Mike va3mw


On Sun, Feb 15, 2015 at 6:31 AM, MontyS <montys at mindspring.com> wrote:

> I echo Don's comment.  My MC-60 mic used to be very sensitive to RF in the
> shack and my monitor used to click on and off,  until I placed common mode
> chokes on the coax leaving the antenna tuner, and on the coax feeding a
> balun outside the shack. (Antenna is an open-wire-fed 80 meter doublet.) I
> no longer have any discernible RF problems, save for my amplified audio
> getting a weak buzz when transmitting high power - and that's probably from
> radiated RF, not common mode.  I have no other chokes on other cables.
>
> Monty K2DLJ
>
> Jeff and all,
>
> I see many hams reporting placing common mode chokes on AC lines, DC
> lines, AUX cables and other lines in the shack.
>
> I am of the opinion that the proper use of common mode chokes is on the
> antenna feedlines.
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