[Elecraft] KX3 atu anomalies - or it is me.

[NU7B]

So...

I think I have an explanation for what I am seeing. My antenna is a
off-center fed stealth random wire suspended from a tree near the QTH. I
feed it via 10 feet of ladder line connected to an SGC130 remote autotuner,
fed by 100 feet of coax into the house. Of course the antenna is the right
place to have a tuner in this situation.

The SGC gets the VSWR usually below 2:1 - but close to 2:1 on 12 meters.
This is not a big deal, but the KX3 PA tended to go into high current at
just over 5W with that impedance, so I use the internal ATU to give the PA a
better match.

This means that I wasn't able to test the "KXAT3 ATU doesn't change things"
hypothesis on a VSWR much less than 1.7:1, because the remote SGC would
always bring it in at least that close. 

Just now I tried the ATU on 6 meters, which the SGC does not cover and
apparently can't detect, since the load remained steady at 2.9:1 during a
tune carrier. When I engaged the KXAT3, it gave me a 1.5:1 solution, and a
subsequent tune carrier read close to that value. So the ATU is tuning the
match to the PA. I engaged the ATU again and it got to 1.1:1, and the next
Tune carrier reported 1.2:1. This is entirely normal behavior for an ATU -
different starting points will often find a different terminal solution. As
for the deviation between SWR reported by the Tune vs the ATU - I have seen
bias in other wattmeters in the reading at one forward power level vs that
at a higher power level. So I don't take a difference of 0.2-0.3 in reported
SWR to be abnormal.

All measurements made off of the KX3 display. I thought I was seeing an
issue, but I think it is now explained.



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