Different SWR on K3 and External Meter

[WK8A]

I just installed the KXV3B board, upgrading from the KXV3A. When I went to
do the 1mW calibration at the end, the calibration failed because the SWR
was 2.9:1 on 52 MHz. I tried a couple more times, with different dummy
loads and cables and found the same result.


I then connected an external SWR meter to the dummy load and found that the
external SWR meter showed a flat 1:1 SWR with the dummy load (as expected)
but the K3 SWR value was always higher, typically 1.4 or 1.5:1 up to 2.9:1
on 52 MHz into the dummy load. The tuner works perfectly on all bands,
however.


Has anyone had a similar issue? I can’t quite tell if the problem is in the
KAT3 or on the K3 main board, and more importantly what the fix might be.
Also, since the 1mW calibration failed, are there any other workarounds?
Many thanks in advance!


73 de John, WK8A
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[John W2XS]

My issue was similar, but with the 50 watt calibration. A recent firmware
upgrade required a 5W and 50W re-calibration. I hadn't done a calibration
since the early days of the radio back in 2008. The radio has worked fine
all this time. It is on almost every day.

With the tuner in bypass, I failed the 50 watt calibration on 52 MHz with an
SWR >2 to 1.  I finally got the calibration to pass by connecting the dummy
load directly to the K3 antenna connector, without the cable. The SWR was
still not 1 to 1 on 6 meters, but it was low enough to pass the calibration.

I chalked it up to a tuner-bypass issue on that band. But I never went back
to take a closer look. I seem to have a lot of RF in the shack on 6 meters
now with my center-fed zepp.  Perhaps better station grounding would help in
that area.

73,  John W2XS



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