In casual conversation, I had an Elecraft developer suggest that
to minimize IMD, you don't want to drive an amplifier with the
K3 output power near the top of the QRP amp range (just below 12
or 13 watts). I generally stay below 10 watts, but would like to
have the 100W amplifier automatically engaged if that will
reduce IMD.
Note: I am sometimes driving my Expert 1.3K amp to 100 watts
output on FT8 just to save the batteries powering my K3. It also
makes it easy to QRO, and I have a couple of FT8 contacts in my
log -- with a DU and a JA -- reporting me at -24 dB where I was
operating at 800 watts. YMMV.
73 Bill AE6JV
On 5/25/18 at 2:25 PM, [email protected] (Jim Brown) wrote:
Right -- it depends on the transmitter design and
implementation. K6XX's work shows that to be true of the K3,
and my measurements (done on 20M as I recall) confirmed it. I
also recall that you noted increased IMD around 15W, which is
likely the result of the K3 firmware causing the power amp to
be turned off and the QRP output stage to be driving the load
at it's full rated power. Under that condition it is consistent
with my (and K6XX's) observations that IMD is often lower at
reduced power output.
-----------------------------------------------------------------------
Bill Frantz | Concurrency is hard. 12 out | Periwinkle
(408)356-8506 | 10 programmers get it wrong. | 16345
Englewood Ave
www.pwpconsult.com | - Jeff Frantz | Los Gatos,
CA 95032
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