[Elecraft] KPA1500 Drive Power

[Rick Tavan]

I've seen some gain drift with temperature, too. I've wondered if there
might be a way to feed back drive power change requests to a K3, or other
radio with adequate command capabilities, to maintain a target output power
(say, 1500w) as the amp warms and cools. This should be done slowly - on
the order of seconds, not milliseconds like ALC. KPA1500 Utility knows its
output power and could be programmed to generate the requests. I don't know
how to get commands into a K3 that has its serial port connected to a
logging program. There are some port-sharing tools out there that might
work, but I'm not familiar with them. In any case, it would require some
engineering at Elecraft. In the meantime, I keep an eye on output and tweak
the drive manually to stay both powerful and legal.

/Rick N6XI


Rick Tavan
Truckee, CA

On Thu, May 31, 2018 at 10:01 AM, john at kk9a.com <john at kk9a.com> wrote:

> My KPA500 also has slightly inconsistent output. If I recall output drops
> a little after the first few seconds of key down. Perhaps it is normal for
> solid state amps as I have never noticed this with a tube amp. This may be
> more of a concern with a legal limit amp if you want to keep it as close
> to 1500 watts without going over.
>
> John KK9A
>
> Bill Stravinsky k3wjv wrote:
>
>  Yup, as the temp climbs the output drops some.  Even though I'm glad I
> got the solid state amp I still prefer tubes, hi.  The drop is anywhere
> between 100 to maybe 300 watts.I never really noted the exact numbers.
> BillK3WJV
> p.s. I'm thinking its a normal solid state thing.
>
>     On Wednesday, May 30, 2018, 4:23:47 PM EDT, K9MA <k9ma at
> sdellington.us> 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
>
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