[Elecraft] K2 + KXPA-100 Question

[Steve Witt]

I have a K2, my first radio, that I've been operating for several
months now. Just purchased a KXPA-100 with the KXAT100 internal auto
tuner option, that I got working today, meaning that I got the keying
circuit prototyped and working so the radio would key the amp. It
seemed to work well and I was able to make a few contacts on FT8. My
K2 has the KAT2 antenna tuner build in. I do not understand how the
antenna tuner in the radio and the antenna tuner in the amp should
interact. At first I had the KXAT100 in the amp in auto mode and it
seemed to be tuning as I changed freqs. Then I tried the 'tune' button
on the radio (sort of to see what would happen) and the antenna tuners
in the radio and amp started tuning. My expectation was that the
KXAT100 would present a fairly stable 50 ohm impedance to the radio
and so the radio's tuner would not tune very much. I noticed that as I
changed bands though, that 'tuning' on the radio caused both antenna
tuners to change quite a lot (judging from the racket the relays in
both radio and amp made). By the way, my antenna is a 66 ft. Carolina
Windom 40m - 10m with about 150 ft of RG-213. Everything in the
antenna/feed system is just a few months old and the SWRs on the
K2/KAT2 have been 1.1 or 1.2. 

So I'm wondering what might be the proper way to control the two
antenna tuners in this setup as I change bands?

73
Steve, N6SAW