Re: Does KPA1500 have these KPA500 characteristics?

Posted by Bill Frantz on May 25, 2018; 10:50pm
URL: http://elecraft.85.s1.nabble.com/Does-KPA1500-have-these-KPA500-characteristics-tp7641171p7641204.html

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, [hidden email] (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.

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Bill Frantz        | Concurrency is hard. 12 out  | Periwinkle
[phone]      | 10 programmers get it wrong. | 16345
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www.pwpconsult.com |                - Jeff Frantz | Los Gatos,
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