[Elecraft] [K3-KPA500] SWR jumps up with 5 second key down

[Don Wilhelm]

Mike,

My first guess is that it is not the coax, but attach a dummy load to 
the antenna end of the coax to test it under full power just to be certain.

The most likely thing is that something in your antenna system is arcing 
at the higher power.  End insulators?  Vegetation touching the antenna 
wire? center insulator arcing? or balun failing at power?

73,
Don W3FPR

On 6/4/2012 1:00 PM, ai6ii wrote:
> I have installed a new antenna and have strange changing swr. When testing
> with RigExperts meter I find good resonance at say 15m (21.200). With the K3
> at 100 watts reading is 1 bar on K3 meter and 1.0 on KPA500 (STBY). When I
> bring the amp online and drive it at 200 watts, all is still good even with
> a 15 second key down period. Driving the KPA500 to 275 watts, still okay
> with key down, although the KPA500 meter now shows 1.1. BUT when I increase
> the drive a little more (300 watts) the swr jumps up to 2.5+ and the KPA500
> shows REFL HI and drops into STBY.
>
> And here is the kicker...NOT ALL THE TIME!
>
> So I think it has to be in the coax. But the 75feet of RG213 is brand new
> premade from Cable Xperts with the connectors.
>
> I will try a different coax. Any other suggestions?
>
>