[Elecraft] KPA100 SSB power control

[Larry Phipps]

I think you are seeing the attack spike of the ALC, Trevor. The LP-100 
responds to very short peaks, apparently faster than the ALC in the rig 
can respond. If you go to www.telepostinc.com/K2_ALC.html you can see 
examples of this. There is a picture I took of CW keying and one Jack, 
K8ZOA took of the response to a tone burst in SSB.

There are two things you can do. One is to back off the requested power 
just a tad, and the other is to look at the value of C36 in your meter. 
If it's not 330pF, then you might want to replace it. That's the filter 
cap in the detector circuit. Earlier meters used 100pF as I recall. I 
increased the value to slow down the response a little. You might also 
want to update the firmware if you haven't recently. You can email 
off-list if you need more info.

73,
Larry N8LP



Trevor Smithers wrote:
> I have just installed a recently constructed KPA100 (including the latest upgrades) 
> and appear to have run into the erratic power control problem.
>
> Using Tune + Display and an external LP100 meter, if I request 5w I get 5w out. 
> Increasing power to 11w so as to engage the pa I also get 11w out - so all seems 
> fine.
>
> Switching to SSB, and speaking steadily into the mic, at a requested 5w I get 
> approximately 5-7w out on each band.
> However increasing the power to 11w I get the following:
>
> 80m  Req 11  Get 45
> 40m  Req 11  Get 80
> 20m  Req 11  Get 25
> 15m  Req 11  Get 30
> 10m  Req 11  Get 20
>
> Reading back through the archive I see that others have encountered the same 
> problem but cannot see a definitive answer to the problem. Anyone have any 
> thoughts as to where to start looking.
>
> 73 to all
> Trevor  G0KTN
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