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

[Willis]

What Antenna are you using?  Not only the balun needs to be rated for your power but the coils and wire does too.  Many mfgrs overrated their equipment.  For 500 watts use kw rated antennas.  RG 213 is good but wire and loading need to be #14.

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On Jun 4, 2012, at 12:00, ai6ii <ai6ii at att.net> 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?
> 
> ..mike
> 
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