[Elecraft] KPA1500 PA Current

[K9MA]

Hi Gary,

I haven’t seen that problem unless the SWR was at least 1.4:1. However, it’s possible you have hit just the wrong phase angle.  If your 1.2 SWR resulted in a load impedance of 42 Ohms, the current could go up 20 percent. On the other hand, 55 A into 50 Ohms sounds a bit high. Make sure the voltage isn’t dropping more than a couple Volts.

73,
Scott K9MA 

----------

Scott Ellington

 --- via iPad

> On Mar 15, 2019, at 1:25 PM, Gary J Ferdinand <alaparos at w2cs.net> 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.
> 
> Suggestions?   I don’t want this to be flipping out during a contest.  I also don’t want to reduce power into what should be a totally acceptable load.
> 
> 73
> 
> Gary W2CS
> 
> 
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