[Elecraft] KPA1500 PA Current

[Don Wilhelm]

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.
>