[Elecraft] K3/KPA500/KAT500 SWR problem
Goldtr8 (KD8NNU)
goldtr8 at charter.net
Mon Dec 30 15:11:50 EST 2013
Interesting as I had a similar problem with my unit on 160m this weekend.
Turned out as I went higher in power I was burning thru an insulator on my
vertical. Thus my problem occurred at higher power until my insulator was
totally gone. Then it was easy to find.
I suspect that that something has arced and now there is a shorting path
that shows up as you go up in power and the KAT500 finds it.
Note I do not use a KPA500 but a different type of amp. I also was able to
watch the swr climb slowly with my W2 as it was slowly starting the
destruction cycle but with lower power the swr was steady. However after
the damage was complete even my antenna analyzer showed the problem. It
took me a bit of time to find the damage before I finally had it nailed
down.
So even though stuff visually looks good and is fine at lower power the coax
could be damaged internally and you are not finding it with the dummy load
as it does not react the same as the antenna because the swr is good.
Just a thought.
~73
Don
KD8NNU
-.- -.. ---.. -. -. ..-
-----Original Message-----
From: Ray Coles
Sent: Monday, December 30, 2013 2:13 PM
To: Elecraft at mailman.qth.net
Subject: [Elecraft] K3/KPA500/KAT500 SWR problem
Forgot to mention that I hauled my MFJ wattmeter/dummy load out to the bush
and pushed up 100 watts into it down the feeder with 1:1 SWR, which
convinced me that at least my UR8 feeder is OK. Also didn't mention I hooked
up my FG01 antenna analyser up at the shack and all seemed normal, but of
course the problem only comes over 40 watts (which equates to a pre balun
500V). THE PROBLEM REMAINS and I am still mystified!
73
Sent from my iPhone
Ray Coles CEng M0XDL
10 Littlemoor Road,
Weymouth DT3 6AA
United Kingdom
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