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Old August 24th 08, 07:03 PM posted to rec.radio.amateur.antenna
Robert Smits Robert Smits is offline
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First recorded activity by RadioBanter: Aug 2007
Posts: 20
Default Size of dummy load required to tune 160 Watts CW, 200 W PEP SSB ?

JB wrote:

For ham goodies look at the specs. Ham stuff usually needs to be more
bulletproof than commercial but it aint'. You would probably be all right
with the 100 watt kit for quick tune-ups unless the fine print says 100w
for
10 seconds. It isn't the 200w pep to worry about, it's the 160 w CW and
FM
and how long you lean on it. Five seconds on and off three times should
be all you need to get it tuned or get a reading.

I have an old Bird Termaline, oil filled, rated for 20 watts that I have
used for years on barefoot rigs. I would never go smaller than that
because the heat may rise too fast and burn the oil and anneal the
contacts of the
load resistor. I have used a big 500 watt Bird for continuous burn-in
(weeks) of 100 watt FM repeaters and Base transmitters though. It is all
about duty cycle and whether the heat can me moved out fast enough to
prevent damage to the resistors and contacts.

Dry dummy loads are a different story. Don't put more than double the
rating even for brief periods unless they are well heat sinked..



I concur. Unless you're going to leave the transmitter keyed up for minutes
or hours even a 50 watt dummy load is quite sufficient to tune up my TS
820S, which has essentially the same finals. Done it for years.
--
(Robert Smits, Ladysmith BC)

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