[Elecraft] KPA500 Question

[Joe Hutchens AJ8MH-Radio]

This is a question I've been wanting to ask...

I've had a KPA500 for 4 years and I've noticed that 20 meters requires 
more drive.  Most bands require 30 watts or less, but 20 requires 35-37 
for 500 watts out.  In the phone portion of 20, an SWR of 1.4:1 WILL 
cause a fault.  It's just real sensitive to the load on 20.  I have to 
use a tuner and make sure I'm close to 1.1:1.  Works fine into a dummy 
load, but high drive is still required.

I've lived with it, because I don't operate SSB very often on any band, 
but lately I've been chasing NPOTA stations and find myself using 20 SSB.

I assembled the amp, and it's been like this from day one.  Anyone else 
see this on 20.  Just interested.

Joe (AJ8MH)