[Elecraft] K3 high SWR at end of transmission

[w2yf]

Ron,

No SWR should not jump from 1.3:1 to 20.9:1... if that occurred then you
likely have antenna issues: a failing coil, water in the antenna line, bad
connectors, poor grounding, etc.

I'm not convinced (yet) that this SWR is real. This SWR reading comes back
from Hamlib as a result of a SW; query issued. The radio itself indicates
absolutely no SWR change on its bar graph. The SWR change only occurs when
transmission is ending. Running WSJT-X in diagnostic mode and going through
the logs I can see the radio is definitely returning these values.

I can transmit for a full minute and the SWR change is only at the very
end. On a faster protocol like FT8, I can transmit only towards the end of
the cycle (4 seconds) and it occurs only at the end, in other words length
of transmission doesn't matter, so it isn't a heating issue. Power doesn't
matter either, it occurs using 3W or 50W. So this isn't a component being
stressed under a load that is failing. I don't believe it is RF on the USB
or audio lines either, as I said, the radio reports it sees this as a SW;
query. When I am not using Hamlib to monitor SWR there is zero indication
that there is any foldback, Hi SWR, or bar graph variance on SWR.

It occurs in the KX3 and K3 (have not had a chance to test KX2 yet). The K4
does not exhibit this behavior, but the K4 uses a completely different
command to return power and SWR states.

The Hamlib readings come from WSJT-X when you check the "Rig Data" boxes on
the "Radio" tab. With their release of 4.7.1 (due out soon) they support
the K-Line and the K4. The K4 was not working properly but that has been
resolved as of the 4.7.1rc.

Tom, W2YF