Kevin:
The duty cycle on FT-8 mode is ~50%. The KPA1500 and KPA500 are both
very adequately rated for this mode and for rated outputs, 1500 watts
and 500 watts respectively.
Your K2 is rated at 10 watts output! At 15 watts, just because it will
do it, is no reason to run that power level. I can understand why the
PA failed. Also SWR will contribute to heating of the PA devices.
Poor antenna match will eat PA devices.
Hams seem to think running at reduced power will "save something". This
is bad ham advice and basically "old ham lore" which is not correct.
Conversely, my measurements show my KPA500 is 38% efficient at 250 watts
and 57% efficient at 500 watts on 20M. This relates to 404 watts of
dissipation at 250 watts and 368 watts of dissipation at 500 watts.
Thus 500 watts is less strenuous, producing less heat on the components,
than 250 watts.
Yes, FT-8 is a weak signal mode. I run near legal limit on 2M to a nice
array just to have a weak signal off of the moon. Low power just won't
get it.
73
Bob, K4TAX
On 6/6/2022 11:29 AM, elecraft-requ...@mailman.qth.net wrote:
From:elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> on behalf
of Kevin Robertson via Elecraft<elecraft@mailman.qth.net>
Sent: Saturday, June 4, 2022 6:52 AM
To: Rick NK7I<rick.n...@gmail.com>
Cc:elecraft@mailman.qth.net <elecraft@mailman.qth.net>
Subject: Re: [Elecraft] KPA1500 reduces power as it gets warmer?
FT8 is a weak signal mode, designed for low power. Given its high duty cycle,
you are asking for trouble if you operate your power amplifier in FT8 mode
using your KPA1500 at anywhere near high power. I burned out my final on my K2
at 15 watts on FT8.
73,
Kevin Robertson KD2WCY
--
IF ONE EXPECTS COMPUTERS AND TECHNOLOGY TO SOLVE THEIR PROBLEMS,
ONE DOESN'T UNDERSTAND COMPUTERS AND TECHNOLOGY
AND ONE DOESN'T UNDERSTAND THEIR PROBLEMS."
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com
