The trouble with any kind of fluid in the can is the can itself. A fluid
with a low thermal resistance still has to get rid of the heat via the
can. If the can had a bunch more surface area exposed to atmosphere,
the cooling would be more effective. As it is, you heat the oil+can,
and wait for it to cool down. That's what I like about my forced air
cooled DL. I can run it all day (unless I run out of air).
Unlike actual RF power resistors and terminators, the TO-220 resistors
are rated full power at 25C, and need to quickly be derated. The Anaren
pn RFP400-50R (http://tinyurl.com/RFP400-50R) that I used are typical,
with a rating of 100C before you need to derate.
vy 73 es gl,
Bryan WA7PRChttp://www.tinyurl.com/wa7prc-dummy
Date: Fri, 4 Dec 2015 12:45:20 -0500
>From: TexasRF@aol.com
>To: hanslg@aol.com, towertalk@contesting.com
>Subject: Re: [TowerTalk] Fwd: Oil For Dummy Load
>
>What is wrong with using distilled water, $1.50 per gallon at Walmart?
>Works just fine for amplifier cooling, no problem at 2000vdc and 1296 MHz.
>Not
>flammable either!
>
>73,
>Gerald K5GW
>
>
>
From: Hans - N2JFS>I dime in the discussion, why not use something with the
lowest viscosity
>such as kerosene. That way the heat would be more efficiently removed.
>Kerosene has a relatively low flam point so, unless you allow the temperature
>to rise too much.
>
>
>I, myself use a home made dummy load made from resistors packed in TO-220
>capsules and mounted on a large, flat heat sink.
>
>
>Hans - N2JFS.
>
>
>
>From: Bryan WA7PRC
>Gary K4FMX asked only about the derating chart.
>
>Fortunately for myself, oil viscosity is immaterial
>since my HN31 won't ever see more than ~ 100W again
>and I'll never need to change the FREE transformer oil.
>
>Instead, for high power stuff, I use my scrap parts
>1500W (100% D/C) DL that uses small flange-mounted
>RF resistors. It's actually smaller than my HN-31.
>
>vy 73,
>Bryan WA7PRC
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