This is nothing unique to the KPA1500: ALL class AB amplifiers behave
this way. Even an "ideal" class AB amplifier has a maximum dissipation
at around half of full output.
One thing running at lower output probably will buy you is lower IMD.
73,
Scott K9MA
On 8/29/2019 08:03, Roger D Johnson wrote:
It's interesting that the heat that has to be dissipated is pretty close
to 1000 watts in all these scenarios! Running the amp at less than full
power buys you nothing.
73, Roger
On 8/29/2019 8:38 AM, Larry (K8UT) wrote:
Pete,
I don't run my amp at full legal limit on digital modes, but
typically set the input power for about 1000 watts output. One of the
interesting characteristics of the amp is increased efficiency as
power increases. At 600 watts efficiency is only 38%, whereas at 1000
efficiency increases to 50% and at 1500 watts to 60%.
(see screenshots)
-larry (K8UT)
------ Original Message ------
From: "N4ZR" <n...@comcast.net>
To: "Elecraft List" <elecraft@mailman.qth.net>
Sent: 2019-08-29 07:59:23
Subject: [Elecraft] KPA-1500 on digital modes
Elecraft's published specs rate the KPA-1500 for 1500 watts output
on all modes. In prepping for this weekend's contest, I've been
running it at closer to 700 watts, because I've found that even just
running on CW, with its much lower duty cycle, my amp reaches 70C
quickly. I don't do that much digital contesting, though, so I'm
wondering whether 1500 watts output is on digital modes is realistic
or a recipe for trouble.
--
73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.
______________________________________________________________
--
Scott K9MA
k...@sdellington.us
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