[Elecraft] 80m KPA1500 High reflected power problems

[Jim Brown]

On 3/9/2019 7:13 PM, Michael Walker wrote:
> You may want to try choking the feedline at the antenna

Always a good thing.

>   and more importantly at the amp end
No, the FEEDPOINT is the most important place for the first choke in any 
antenna system.  The purpose of a second choke on an antenna like a 
dipole is to prevent it from acting as a parasitic element to a nearby 
vertical.
> with mix 31

Yes.

> or 43 chokes.

I've recently completed a year's worth of extensive lab work that has 
convinced me that #43 is NOT a good material for HF chokes. Ditto for 
the #52 material that G3TXQ recommended. Two characteristics combine to 
make it a poor choice. First, it's a relatively high Q material, so the 
resonance it produces can get very narrow. Second, like all Fair-Rite 
parts, it's a wide tolerance part -- +/- 20%.  A part at the low end of 
the tolerance range will produce a very different choke (resonance in 
the wrong place, very narrow bandwidth, wider resonance and not high 
enough impedance.

That work has produced, among other things, an all new cookbook with 
greatly improved designs.  k9yc.com/2018Cookbook.pdf

As to Peter's problem -- I'm inclined to agree with Don that something 
may be arcing in the antenna system and causing a true fault.

73, Jim K9YC