[Elecraft] RF feedback

[Vic K2VCO]

Richard S. Lindzen wrote:
> I'm running the K3 with an Ameritron AL800 and a Steppir 3 element with 
> 40m dipole add-on.  I have a severe though intermittent feedback problem 
> on 40m that I did not have with an Icom 751a.  The feedback only occurs 
> when I'm using the amp (even with very low drive).  I've common core 
> choked virtually every lead with ultimately no luck.  I'm using the 
> Elecraft hand mike.  Is there a known problem here?  Otherwise, I'll 
> just keep searching.

There is a so-called "pin 1 problem" in the K3's mic input circuitry. The fix is to jumper 
L4 on the front panel board and L7 on the KIO3. These are RF chokes in the mic return lines.

I have not done this yet myself, since I am a CW guy! But I'm sure Elecraft support can 
provide you with detailed instructions for doing this if needed. The mod has solved RF 
feedback problems for several K3 owners.
-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco