[Elecraft] Topband RF feedback problem

[Stewart Baker]

Are you using a separate RX antenna ? There is a recognised issue 
with the KXV3 and insufficient isolation  that can give rise to 
spurious oscillations.

73
Stewart G3RXQ
On Sun, 10 Feb 2008 21:43:55 +0100, Björn Mohr wrote:
> I had my first weekend with the new K3 and bumped into a strange 
problem. It
> actually took me a while to figure out what was going on. When 
keying up
> with the amplifier in line on 160 I was not able to run more 
than 400 watts
> before the SWR protection in both the amp and SWR meter kicked 
in, it all
> happened in milliseconds as if arcing was going on somewhere. I 
thought I
> had an antenna problem and went through the system without 
finding anything
> strange. After some time I hooked up my MP and all was fine 
again, running
> full power without a problem. That's when it hit me - RF 
feedback had to be
> throwing my K3 off frequency and therefore tripping SWR 
protection and the
> alarm.
>
> My setup has been working fine with the MP for over a year, 
never seen a
> problem like this. A common mode choke is in line with the TX 
antenna and
> most of the wiring used with the MP was used for the K3 except 
that power
> where fetched from my 12 volt bus. The MP is a field model and 
gets its
> power straight from the mains, same phase as the 12 volt bus.
>
> I would be interested to hear if anyone else had similar 
problems and found
> a good solution.
>
> 73 de Björn /SM0MDG
>
>
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