Triage the problem...
Dummy load at the end of the tuner chain-- if it works at high power
then all is good from the dummy load back, the problem lies downstream
of the dummy load. If it fails with the dummy load there, then you have
a coax problem between the radio and the dummy load.
So far you have done a bit of triaging already, if you operate on the
vertical, with no tuner, and all is good, then you know the radio and
amp are OK. You also know the feed line to whatever type of coax switch
you have is OK...
Move the dummy load around to triage out as much as possible...
If you don't have a dummy load, you need one... Every station needs a
dummy load just for this sort of testing.
73s and thanks,
Dave
NK7Z
https://www.nk7z.net
On 2/24/2018 12:42 AM, Chris Hallinan wrote:
Greetings from southwest Florida.
My KPA500 is kicking out with REFL HI warning (high SWR). But here is
the
strangeness. My setup is K3->KPA500->40' coax->MFJ 600W remote tuner
-> 4:1
balun -> open wire feedline to 80-meter doublet. In words, I have a
remote
autotuner feeding an 80-meter doublet fed with 600-ohm open wire line. A
Balun Designs 4:1 balun provides the interface from the open wire line to
the tuner.
With the autotuner tuned at low power, the SWR shows 1.5:1 on my
KPA500 and
external SWR meter. As I run the power up to 300, 400, 500 watts,
somewhere in there all of a sudden the SWR instantly jumps off the scale,
into the red LEDs on KPA500, and it faults. It's as if the SWR were
dependent on power.
Even stranger, when I back the power off to say 250 Watts, holding key
down
the SWR is stable in the green (<1.5:1), but when I key it at CW
rates, the
SWR bounces into the red on every dit and eventually faults, when at
steady
state key down it never leaves the green zone!
I fear it is the tuner falling over, but it should be able to handle the
power. I see this on all bands from 80-20.
Operating into my 20-meter resonant vertical, with no tuner, everything
works fine.
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