[Elecraft] KPA1500 Drive Power

[K9MA]

Now I'm really confused.  I observed the power drop when operating 
several times, as described below. However, I just ran a test, both with 
an antenna and a dummy load, and saw only a very small change in output, 
perhaps 50 W, which is inconsequential.  I even tried simulating CW 
operating in QSK mode.  I can't think of anything else which has 
changed.  In each case, I'm reading the power output on the KPA1500 
display, but it appears consistent with the P3 TX monitor.  Any ideas?

BTW, the specs I've seen for LDMOS FET's like the ones I presume are 
used in the KPA1500 show quite a small variation in gain with 
temperature.  Feedback should reduce that further.  That would be 
consistent with my test results, but not the operating ones.

I'll do some more "real" operating in a couple days and report the results.

73,
Scott K9MA

On 5/30/2018 15:19, K9MA wrote:
> I'm using the K3 with the Elecraft interface cable.  I've noticed the 
> the CW drive power required by mine varies considerably, both with 
> temperature and SWR.  If I set the K3 output for a KPA1500 output of 
> 1500 W output initially, the output will drop to perhaps 1100 W when 
> the temperature stabilizes at around 65 C.  (I've ruled out any change 
> in antenna impedance, etc.)  A similar change occurs if the SWR goes 
> from 1:1 to 1.2:1 when changing frequency or switching antennas.  I 
> haven't changed the ALC from the default setting.  Has anyone else 
> noticed this?
>
> 73,
>
> Scott K9MA
>

-- 
Scott  K9MA

k9ma at sdellington.us