[Elecraft] Fault on KPA500 after 300w

[Brian D]

I had a similar problem but only on 160m. would work fine for a few minutes
at full power, fine at reduced power. After much hair tearing discovered
that it was a voltage transformer in an external coupler heating up and
losing inductance, effectively shorting the feeder. Cured by using a larger
toroid in the coupler.

Brian G3VGZ



"john at kk9a.com" <john at kk9a.com> wrote:

> A dummy load may verify that the KPA/KAT are working properly. I am
> guessing that something is arcing in your antenna system. Perhaps water
> ingress. Have you run high power into it with a different amp?
> 
> John KK9A
> 
> 
> 
> On March 12 Alan Lambert wrote:
> 
> I recently acquired a KP500/KAT500 for use with my Kx3/KXPa100. I know the
> person I bought it from well and I am 99.9999% sure it is not an issue
> with the amp or tuner.
> 
>  I was making some notes (a chart) for input to output power levels,
> mostly just to ‘get to know’ the amp a little better.  At the time of
> these issues, I was on 80m SSB and the Kat500 was showing 1:1 / 1.2:1.
> 
> The output watts  I have listed below are not ‘actuals’ I’m just recalling
> them from memory so may be off a few watts.
> 
> I set the Kx3 to 8w and called “test test test 1 2 3  kn4bbc” I showed
> ~80w out with a 1:1 to 1.2:1 SWR.. GREAT!
> 
> Moved up to 9w and got 100w out… same SWR – more Great!
> 
> 10w I got 175w same SWR – sill looking good!
> 
> 11w I got  250w same SWR – Awesome!
> 
> Now this is where the problem comes in.
> 
> I set to 12w… As I starting calling my “test test test 1 2 3…”  At first
> things looked great..I was getting 300w same SWR  but then suddenly I get
> high SWR followed by  “High Refl” on the KPA5, fault light comes on and I
> get warning tones.
> 
> So I tuned the KAT500 again and tried the whole thing again with the same
> results.
> 
> Gear wise:
> 
> KX3/Kxpa100 with ATU disabled > KPA500/KAT500.
> 
> Ant1 on Kat500  >  1ft LMR400 jumper >  1:1 ATU Current Balun  > 225 feet
> of 450 ladder line > a ½ wave 80m center fed, inverted V  dipole. Center
> point is ~90 feet off ground.
> 
> The Balun is a Balun Designs Model 1161
> 
> The shack is on 2nd floor in middle of the house and has no exterior
> walls.
> 
> The ladder line starts in the shack, there is about 2 feet  of in the
> shack then enters my attic space thru and opening in a sheetrock wall.
> Inside the attic space there is a long slow, wide loop about 50 feet long.
> I was careful to keep it away from metals and it does not cross itself
> however some of it  is lying on top of plywood. From there its exits the
> house in the ridge cap at the tip top of the roof at about (40 feet off
> ground)  The ladder line then hangs from a rope that runs from the eve to
> the tree line about 175 feet away which is where the center point of the
> dipole is.  In short 175 feet outside 50 feet inside.
> 
> 
> Ideas of what my problem might be?
> 
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-- 
Brian D
G3VGZ  Yarm    England