[Elecraft] [K2] KPA100 - Antenna Help

[Don Wilhelm]

David,

I just thought of something else - the KPA100 may be oscillating on 
you.  That fact will not show up on a dummy load, but because an antenna 
is frequency selective, it will indicate Hi-refl.  The KPA100 *should* 
detect that condition and reduce the power, but for some reason yours is 
not. and I strongly suspect the T/R switch area.

Check the T/R switch components carefully - particularly the orientation 
of Q6 and Q7 and the diodes.  Also check the soldering for C31.  Make 
certain the value of C31 is .22 uF.

Since you likely do not want to test on-the-air with that condition, if 
you have a tuner (preferrably a link coupled tuner), connect the output 
to a dummy load and then adjust the tuner for a 1:1 SWR at the frequency 
you will be testing.  If the KPA100 is oscillating at some parasitic 
frequency, Hi-Refl will be indicated because of the tuned circuit 
between the KPA100 and the dummy load.

73,
Don W3FPR

David Douglass wrote:
> OK, to add to my last,
>
> I've just tried with a different antenna on 40m. Again, once I engage the KPA100, I get high SWR, power overshoot and a blown fuse. So it doesn't seem to be antenna related but seems to be band related. 30m-10m is Ok. I don't have an antenna for 80/160 so can't check.
>
> All bands are fine with a dummy load...
>
> David
>   ----- Original Message ----- 
>   From: David Douglass 
>   To: elecraft at mailman.qth.net 
>   Sent: Saturday, June 12, 2010 12:04 PM
>   Subject: [K2] KPA100 - Antenna Help
>
>
>   Hi All,
>
>   A bit of a strange one here..
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>