[Elecraft] KXPA100 driving AL-800H

[Al Sather]

Greetings All

I am having a problem with my KXPA100 driving my AL-811H.

First what works

KX3 driving AL-811H no problems, and at 10 watts drive I get over 125 
watts out, about what I expect.
KX3 driving KXPA100 no problems, and performs as advertised, and tested 
to 90 watts.
KX3 using my KXPA100 to drive AL-811H which has out put pretty much as 
expected (approx less that 40 watts in with more than 400 out)

It should be noted my all f/w etc.  is up to date, and today I replaced 
the power amp drivers with the most recent beta version. This did not 
help, as expected. Also, the ATU in both the KX3 and KXPA are bypassed, 
since there is a third antenna tuner in line to handle the high power 
from the AL-811.

Now the problem! My Rx was attenuated from a S7-S8 signal to a S1-S2 
while working the Elecraft SSB net this morning when the AL-811 is 
keyed, even briefly (i.e just a dit).
Turning the 811H off and on or going from "opr" to "stand by" restores 
the Rx to normal. While talking with the net, I was Txing nearly 500 
watts, but needed to go from opr-stand by, to copy net control. Tx was 
not affected.

I have carefully followed the suggested wiring by the KXPA100 user 
manual as shown on page 14. If I use the Key line found on the KXPA100, 
I still get attention of the Rx upon termination of Tx.

Up until today, the KXPA100 has performed flawlessly and a joy to 
assemble and to operate.

My question is, ``Where may the fault lie``.
Changing the ``Opr`` status resets the attention in the AL-811H. 
Suggests an AL-811 issue.
But, only when the KXPA is part of the circuit, Rx attenuation occurs. 
Suggests and KXPA issue.
Or, these two amps just do not each other ;-(

If I set the power level, say to 2 watts, the KXPA should not fire as a 
PA, but it is still part of the circuit, and Rx attenuation occurs. 
Could there be a grounding isssue.

The KX3 is able to drive the AL-811 without issue.


Any suggestions as to what I can do next, or where should I look for an 
issue.

Thank you
Al, ve7ear
apsather at shaw.ca