No ... overheating doesn't take much time at all.
As I stated in my reply to Bill, high power and high VSWR will indeed
heat up a ferrite core device ... balun or common mode choke ... and it
can do so quite quickly. In my case, I had a 160m Inverted-L that I put
up rather hastily for a contest and I didn't trim it for best match. At
100 watts it worked fine because I could tune it at the shack, but at
anything above 1,000 watts the ferrite core in the common mode choke
would heat up and fault the amplifier (QRO Technologies HF-2500DX tube
amp) in less than two seconds. This happened repeatedly, and when I got
serious and fixed the antenna for a lower VSWR everything was stable
even at 1500 watts and even with the same choke that I luckily hadn't
permanently destroyed (although I suspect the core had been compromised
for original choking performance).
High VSWR is very tough on ferrite cores.
Dave AB7E
On 9/2/2020 6:07 AM, Adrian wrote:
Overheat is a situation taking time, and usually starts with a good
match, then deteriorating.
In this case ; "But when I throw the KAP1500 in line, it gets all
pissed off, throws up and faults out. Says SWR is 99:1 !!!"
indicating an instant issue while the balun is still stone cold...
The 5kw balun is not the best for your situation, but rather the 4116
3KW hybrid
https://www.balundesigns.com/model-4116-4-1-hybrid-balun-1-5-54mhz-3kw/
See ;
https://www.balundesigns.com/blog/baluns-for-multiband-antennas-fed-with-open-wire-or-ladder-line/
73
Adrian Fewster
On 2/9/20 10:12 pm, Bill Johnson wrote:
I would agree that the coil could overheat. The model number is left
out. The Balun Design coil chosen may not be satisfactory for your
power despite the 5KW rating. Which Balun are you using?
Bill
K9YEQ
-----Original Message-----
From: [email protected]
<[email protected]> On Behalf Of David Gilbert
Sent: Tuesday, September 1, 2020 12:28 PM
To: [email protected]
Subject: Re: [Elecraft] my KPA1500 and 160M
One distinct possibility is that the 4:1 balun is getting hot at 1500
watts. Have you tried running the KPA1500 at a lower power?
73,
Dave AB7E
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