Bill, ok on that, yes more electronic amplifiers especially use a swr
limit to protect against the high voltages
generated at high swr. Sometimes you are better off using a robust
manual tuner made for the job external to the amp.
High swr between a remote balun and atu at amp, will emphasis balun
heating loss as the signal passes the feedline length many times before
totally dissipating in the coax loss & balun core,some as heat loss, and
some as desired induced balun current to antenna radiated RF.
Ladder line back to a close-by matchbox, which can handle KV, close to
amp, would give best power efficiency, as ladder line has minimal
feedline loss.
I would be using a manual ext tuner with this type of antenna, also
taking away risk of damaging the amp.
On 3/9/20 2:19 pm, K8TE wrote:
Nowhere has there been a mention of what VSWR the tuner sees, only the result
of its match which is 2.5:1.
That means the VSWR it sees is beyond its capability to tune properly and
run full power. This information is available on the KPA1500 panel display.
It will also state the maximum allowable power output. What are those
values?
I suspect the VSWR is quite high and the allowable power well below 1,500
Watts. It's likely you're expecting more power-handling capability than the
BALUN, either one, can handle.
When one writes "quickly" that is interpreted differently by all those who
read it. Obviously, 20 to 30 seconds is not "quickly", at least to me, but
a very good indications of something overheating, but not instantly. The
latter could lead toward a very different conclusion.
My current (pun intended) conclusion is don't run over 800 Watts on 160m!
That is about the same level you run with your other amplifier without a
failure, maybe, if you don't run it too long at that level. I'm glad you
concluded it's an antenna system problem.
BTW, W8JI has written about this antenna and recommends an 80-20% ratio,
rather than the typical 67-33% ratio. He has modeled it for various bands
on his web site. I don't know why the common 67-33% values are used when
someone has shown there is a better choice. Old habits, good and bad, die
hard.
73, Bill, K8TE
--
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