Posted by
Doug Turnbull on
Feb 10, 2020; 9:37am
URL: http://elecraft.85.s1.nabble.com/QRO-KPA500-Failure-tp7658244p7658338.html
Andy,
Yes, you are right and this applies to both KPA 500 and KPA 1500. The
conditions for maximum efficiency are not necessarily those for minimum
dissipation or reduced stress. I would like to know if running 2/3, 1/2
or even 1/4 maximum power output increases reliability and MTBF. It would
be a considerable surprise to me if this were not the case and it would be
good to know the numbers. Improvement in MTBF can be several fold for
some devices for a reduction in voltage, current or power of as little as
10%. Good design practice normally means that this is part of the
engineering design process. The proof of derating is looked for in design
reviews. Too many hams run their amplifiers flat out for very little
benefit. Signal cleanliness is still another issue; higher voltage but
lower power seems to help here.
Using FT8 or WSPR on dead band (160M in daytime or 12M), I sometimes
run 20 Watts plus. This can be stressful on the K3 especially for WSPR.
I crank the K3 down to a watt or so and drive the KPA 1500. Yes, my total
energy consumption is no doubt up but stress on either K3 or KPA is minimal.
This however is not my concern, I would like to know if running the KPA at
lower power increases reliability. In EI we can run 1500 Watts for
contests but outside of contests can only run 400W max.
73 Doug EI2CN
-----Original Message-----
From:
[hidden email] <
[hidden email]> On
Behalf Of Andy Durbin
Sent: Monday 10 February 2020 01:45
To:
[hidden email]
Subject: [Elecraft] QRO - KPA500 Failure
"I am seeing a lot of confusion and erroneous conclusions based on the terms
'efficiency', 'dissipation' coupled with 'power output'."
Yes, very true. Only a few have actually contributed test data. All the
rest is assumption and speculation.
Andy, k3wyc
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