Gary,
Have you considered that there may be something in your antenna system
that is heating up or otherwise changing with the 1500 watts power?
The first thing I would suspect is a balun that is heating, or a
connector that is not quite tight enough.
Those kind of problems will not show up at lower power, but at 1500
watts may become troublesome.
73,
Don W3FPR
On 3/15/2019 3:25 PM, Gary J Ferdinand wrote:
I’m in the process of checking out my amp. I have two dipoles (40 and 80). At
resonance both show a 1.2:1 SWR with ATU totally bypassed. With ATU on, it
remains bypassed on 80, but shows only the ATU ON LED on 40. In both cases the
resultant SWR is 1.2:1. SWR measurements are from the KPA1500 display.
When I use the amp with my K3 and drive it up to 1500W, I am occasionally
getting an excessive PA current fault at 63A. From a cold start it’s 60A, but
as it warms up in contest usage I find the power drops off, so I have to adjust
the K3 to bring it back up to 1500W. At that point the PA current goes over
60A.
Interestingly, into a dummy load the 1500W point shows a PA current of only
55A. So the 1.2:1 SWR, be it via a bypassed ATU or using the ATU, is
sufficient to raise the PA current eventually to excessive levels.
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
