[Amps] Dummy Loads & Carborundum Resistors QRO

BEAR bearlabs at netzero.net
Wed Jun 25 13:45:26 EDT 2003


Anyone out there have solid technical information on Dummy Loads &
Carborundum Resistors??

My old Heathkit Cantenna has a ~1" dia x ~5" (iirc) grey carborundum 
resistor,
sitting in a can of oil. (rated 1kw short time)

I've been offered a batch of ~1" x 18" carborundum resistors @ 50 ohms
and/or
a batch of  ~2" x  18" @ 25 ohms - these are said to be rated at 750 watts.

Here are my Q's:

If the latter one is rated at 750 watts, what is the dry rating of the Heath
likely to be??
(the heath is asymptotic to 200 watts over time...)

What is the bandwidth likely to be ??
(the heath is <1.5:1 up to 300 mhz.)

If I put it in a bath of transformer oil, what is the increase in power 
handling?
(does the added surface area play in to this??)

I'm thinking that unless there is something wierd about these resistors that
the 50 ohm unit ought to be at least 500 watts in air, or more... the 25 
ohm
unit would seem to be rated very conservatively, yes?

I've owned a bird style >2kw unit at different times and they seem to be 
about
this depth and have fins for cooling (of course) - do they just leave 
some air in
the chamber for heat expansion of the oil, do they have a blow off vent??

What else should I know???



        _-_-bear

-- 
  _-_-bearlabs

   http://www.bearlabsUSA.com
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