K3 Single Band SWR problem

[Phil Salas]

Craig - I had a very similar problem.  I was operating on 20 CW into my
non-resonant antenna (SWR about 7:1) using the internal tuner.  All of a
sudden I had a high SWR.  My Powermaster showed that the external antenna
system hadn't changed.  I was able to have the K3 ATU re-tune, and then
everything was OK again.  However, I laterr found tha my SWR was high on
some of the high bands whne looking into a dummy load.  It was 1.2:1 on 17
meters, about 1.5:1 on 15 meters, about 2:1 on 12 meters, and 1.5:1 on 10
meters.  This occurred with the ATU bypassed on both A and B outputs.  Fine
on all other bands, including 6 meters.  I stepped through the relay
switching manually to make sure I could hear each "click", and all relays
seemed to be working fine.

When I was unable to find any problems, Elecraft replaced the ATU and
everything has been fine since.  But this was very puzzling.  If a ATU relay
contact had failed so that a component was in-line all the time, I'd expect
things to get worse as you went higher in frequency. - not peak and then get
better again  I also considered that maybe a MOV in the ATU had failed.  But
there are separate MOVs for A and B outputs.

OF course, as long as the ATU would tune OK, I could continue to operate.
But I could no longer set the power at 5- and 50-watts properly on 15-, 12-,
and 10-meters.with the tuner bypassed.

Anyway, replaceing the ATU fixed the problem for me, but I'd sure like to
know what the problem was.

Phil - AD5X

"My first real problem (or operator error?) with K3 SN 608 just occurred.  I
got on 20 CW with my usual antenna (a resonant dipole) and the K3 is showing
a 2:1 SWR and folding back power.  I bypass the tuner with this antenna
since its SWR is in the 1.2 to 1.3 range.  My external SWR meter shows the
usual 1.3.  If I engage the K3 tuner it will tune to a 1:1 indication on the
K3 meter and register the requested output power, but the actual output
power measured externally is in the range of 70 to 80 W for 100W on the K3
meter.

Next I tried a known good dummy load and the K3 acts the same with it -
indicates a 2 to 1 SWR.  Interestingly, it works fine with the dummy load on
all the other bands (shows 1.0 to 1 SWR) except 20.  It has worked fine
before on 20 with this same antenna and as far as I know nothing has
changed.  I'm running firmware version 1.78.

Will welcome any ideas or suggestions

          Thanks
                       ... Craig  AC0DS"

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