[Elecraft] K3/100 low power setting "gap"

[Fred Townsend]

Hi Felix:
Don't we all wish we had your problem. One work around would be to put a 3db
pad between your K3 and your amp. That might help your IMD too. Just a
thought.
73
Fred, AE6QL

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Felix Hormuth
Sent: Thursday, October 8, 2015 12:20 AM
To: elecraft at mailman.qth.net
Subject: [Elecraft] K3/100 low power setting "gap"

Dear all,

I have a kind of luxury problem concerning achieving output powers in FSK
between 9.5 and 13W. The setup: a relatively new K3/100 with the last
firmware a recent TX gain calibration. I'm doing a lot of RTTY, mostly in
submode FSK D. Now I hooked up a 1K-FA linear amplifier which has quite some
gain. For serious work in RTTY I'd like to settle around 500W output, i.e.
half max.
The ideal input power for that would be somewhere between 10 and 12W.

Now the problem: for powers below 13W only the LPA is active. The output
power in RTTY goes up to 9.5W but not further, regardless if I set 10, 11,
or 12W. When I increase to 13W the KPA3 kicks in and I get ~13.5W.
So at the moment I cannot reach the 'sweet spot' that would be required for
my desired 500W RTTY.

So the questions are:
- Is the LPA capable at all for CW output of 10-12W or does that only  apply
for PEP in SSB? Are 12W only possible w/o KPA3 installed?
- Has someone an idea for a good workaround?

So far I only came up with the idea to manually mis-"calibrate" the TX gain
in order to reduce the overall output so that I start in fact with ~10W when
I set the output to 13W. That'd limit the maximum output to below 100W but
that would actually fine for me. Without PA I'll be doing only PSK and JT65,
and for that 50W are more than enough.
However, that's a rather nasty solution and if anyone has a better
suggestion I would be happy to hear about it.

vy 73,
Felix DL2FHO





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