[Elecraft] K2 + KXPA-100 Question

[Grant Youngman]

I would think the KAT2 should be bypassed.  The KX3 internal ATU is automatically bypassed, perhaps the KAT2 is not? (Don’t own a K2, but there should be no need for the internal tuner to be active).


Grant NQ5T
K3 #2091 KX3 #8342

> On Aug 13, 2018, at 11:22 PM, Steve Witt <sawitt at ieee.org> wrote:
> 
> 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?
>