[Elecraft] K2/100 #4198 PA Stability Problem?

[Earl W Cunningham]

Vic, K2VCO wrote:

"I have an Alpha 86 with a huge Hypersil transformer in it, and there's
no problem with a separation of about 4 feet (1.2 m).  I did have
problems with an antenna rotator control box which contains a much
smaller transformer until I moved that about 18" (46 cm) away."
----------
Perhaps my ears are more discerning than Vic's.  I only became aware of
the problem while field testing the K2 click mod on my unit and using
very narrow CW bandwidths on the monitor receiver.

Even when I replaced the KPA100 with the original top cover and drove the
amp with the straight K2 (manually keying the amp) the problem exists.
(It was interesting to find that the ~13 watts out of my K2 would drive
the amp to ~400 watts output).

I also tested it at N6JZ's QTH driving his new Alpha 99 and the same
identical problem existed.  Clean barefoot, dirty driving the amp. 
Manually keying the amp made no difference.

Just because nobody alerts you of a problem with the cleanliness of your
signal doesn't mean that a problem doesn't exist..

The K2/100 is absolutely clean running barefoot, but dirty when driving
an amp (unless the amp is far enough away from the K2 so that the amp's
transformer field doesn't get into the K2).

73, de Earl, K6SE