[Elecraft] K3: SSB Audio Stops-Quits-Kaput on 160

[Don Wilhelm]

Lee,

Have you installed the Front Panel Microphone Circuit Modification in 
your K3? 
http://www.elecraft.com/K3/mods/K3_Application_Note_Front_Panel_Microphone_Grounding.pdf
I would do that as a first step.

If that does not cure your problem, then I would suggest work with the 
antenna system to get rid of the 160 meter 'RF in the shack' - perhaps 
in your situation, some sort of artificial ground may be necessary.  One 
thing for certain, that ground rod will not act as an adequate RF ground 
(ground rods seldom do).

Since you suspect RF feedback problems, I would make a quick check by 
operating into a dummy load - if you still have a problem, it is not RF 
induced, and you can call it a real K3 problem.

73,
Don W3FPR

Lee Buller wrote:
>
> Here is the scenario....
>
> NAQP Contest - SSB
> 100 watts
> Heil Headset with HC-4
> Using VOX
> Connected to the front (not the back)
> Only 160 meters
> Antenna - Inverted-L with feed point less than 10 feet from the K3
> Radials - 20 random length radials in the yard.  City lot
> Tuned using a Palstar AT2K
> SWR - none (I am tuned)
> Station Ground:  8 foot ground rod right below the desk tied to single 
> point
>
> Narrative:  I am calling CQ (of course you do this many times during 
> the course of the contest) and the audio on the K3 stops - quits - 
> nil.  I can shout in the mike, but nada.  K3 is in Xmit mode...using 
> VOX.  No audio output can he heard in the Monitor (headphones) and not 
> meter movement or output occurs.  Stop speaking...VOX drops.  Call CQ 
> again, does not happen this time, but three times later....audio stops 
> on xmit.  Place a choke bead on the Heil Mic adapter, does not help, 
> still quits.  Reduce power to 90 watts.  Still does it.  160 meters is 
> the only band this occurs.  Did not happen on CW during NAQP CW.
>
> RF induced?  This is the only thing I can come up with.  Anyone else 
> seen this or has an idea to fix it - except ideas should not included 
> quit contesting, stay off 160 meters, sell the rig, etc. etc. etc.  :>)
>
> Lee - K0Wa
>
>