[Elecraft] Re: K2 RF Feedback

[Stewart Baker]

On Mon, 12 Jul 2004 11:50:46 EDT, Unifiedtx at aol.com wrote:
> Hello Stewart,
> I have experienced "fuzzy" transmitted audio with my K2/100,KAT100-1 on 75
> meters also.  My KSB2 has all the KI6WX mods and has a bandwidth of 2.5 Khz. 
> It looks great on Spectrogram, and the received audio is excellent.  I have
> two K2s (both with KI6WX mods) and they both sound fuzzy so I suspect it is
> an RF feedback.  I removed the Elecraft MH2 (electret) mike and removed the
> 5.6K resistor across pins 1 and 6 of the mike connector and connected the
> Kenwood dynamic mike that came with my TS-850.  This mike seems to clear up
> the problem and I am getting good clean audio reports.  This seems to mean
> that the RF is getting into the mike input.  I also did the mod to ground the
> mike connector, but I don't think much of that mod, and don't think it helped
> much if at all.  Now I will have to tackle the same problem in my older K2. 
> BTW, my hamshack is on the second floor of my garage.  This can present some
> challanging grounding "opportunities".  Anyway, I thank you for sharing your
> remedy with us by using the RF choke in series with C32 on the KSB2 board. 
> Roy Morris  W4WFB 

Roy,

Thanks for your mail. Although I am using a balanced antenna system, on some 
bands particularly 40m there is still a significant amount of RF in my shack.
Your grounding situation will be a lot worse (been there, done that, got the Tee 
shirt !)
It only needs a small trace of RF getting into the audio side to make your 
transmission sound "fuzzy". The RFC mod I did got rid of all the RF feedback 
problems I was getting, without affecting the TX audio frequency response one 
jot. Anyway, putting it in can do no harm.

73
Stewart G3RXQ