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Old August 21st 08, 07:54 PM posted to rec.radio.amateur.antenna
JB[_3_] JB[_3_] is offline
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First recorded activity by RadioBanter: Apr 2008
Posts: 543
Default Size of dummy load required to tune 160 Watts CW, 200 W PEP SSB ?

wrote in message
...
My old TS-520S is said to put out 160 watts DC CW and
200 watts PEP SSB .
Whats the minimum dummy load requirement to tune it ?

There are kits for 100 watt dummy loads. Would that be
enough for brief ( ~ 10 sec ) tuning ?

Are there standards as to how the rating of a dummy load
is to be interpreted ?

Dave WB3DWE Temple, TX


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..