[Elecraft] KPA100 with KAT100 oscillation?

[Vic K2VCO]

Someone recently posted a problem similar to this.  Of course I didn't 
pay attention to the answer!

I recently changed the configuration of my station to connect an antenna 
directly to the ANT 2 output of the KAT100.  Previously, it was 
connected through an automatic switching system, ultimately getting to 
the ANT 1 output.

It's a reasonably well-matched 40 meter vertical.  There's a choke balun 
on it.  I never had any trouble with it.  But with the new 
configuration, the KAT100 shows a matched condition up to about 60 watts 
output.  As power was increased above that, the indicated SWR starts to 
increase, shooting up rapidly to the 'all LEDS lit condition'.

I 'fixed' the problem by adding about 6 feet to the coax feed to the 
antenna.

My feeling is that the KPA100 is for some reason oscillating away from 
the operating frequency when it sees a particular kind of load, which 
the KAT100 is providing as a result of the load *it* is seeing!

I hope that's clear.  I'll try to determine the frequency after this 
coming Sweepstakes weekend.

For what it's worth, my KPA100 has all of the latest modifications, 
including the shield kit, care paid to the RF choke location, etc.


Any comments?
-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco