AS I read "Re: [Elecraft] KAT100 project - removing the control
board", Stan related his troubleshooting adventure and found that his
assumptions led him astray. That is one of the cardinal issues with
troubleshooting - do not assume. As soon as you assume soemthing is
OK that will be what you eventually will find wrong.
Case in point was a problem I was seeing with SWR read by the KX3 at
some frequencies in the HB TR switch that I was testing. On HF I
figured there would be little distributed inductance and reactance in
the pc board. I tested at 10w using the KX3 on the work bench and
got excellent SWR and transmission loss thru the pc board relays
until I got to 17m, 15m, and 12m. Strangely, 10m tested good?
On those three bands the SWR went to heck. Trying several things to
compensate got me nowhere. I finally reconnected the input coax at
the same land as the output coax and still was seeing this effect -
huh? I began to suspect the KX3 internal circuits had gone bad on
those bands. So I connected a coax direct to the power meter and
50-ohm load (SWR still high). Then is dawned on me. I was running
with the ATU enabled and it had memory of previous loads that were
not 50-ohm.....duh! I switched to BYP and retested and the SWR
problem went away for nearly all bands. There was a little creep up
on the highest frequency (12m and 10m), but that is expected as
circuit dimensions become significant in wavelength.
From the workbench,
73, Ed - KL7UW
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