My hb 50 ohm dummy load consists of 4 x 200 ohm globars in parallel [type
SP, glass bodied
and suitable for oil immersion]. Each resistor is 1" diam x 12" long. [275 W
CCS in air]
Each resistor resides inside it's own 2.875" OD x sched 40 Aluminum tube.
All 4 x thick walled AL tubes are heliarc welded.
I heard some place that instead of xfmr oil, that distilled water can be used
instead?
The same glass bodied type SP resistors, [50 ohm, high wattage] are used in
water cooled loads,
the type that has the garden hose on one end, etc.
Seems to me that distilled water will conduct heat a lot better than xfmr oil.
The question is,
will the use of distilled water in a 7 gallon metal container, with resistors
immersed present any
swr problems ? If I remember correctly, swr was high on heath cantenna loads
if no oil used at all,
and dropped to dead flat once the oil was poured in. There was also a similar
50 ohm load in the
old arrl books, same resistor as I'm using but it was a single 50 ohm unit, and
not 4 x 200 ohms in parallel.
I would prefer not to use xfmr oil if at all possible. It's a little tougher
to get a hold of these days..and not cheap.
My main concern however is something leaks. Water on the concrete floor in the
shop is one thing, but 7 x
gals of xfmr oil is a disaster. Can you add rust inhibitor's or glycol to
the distilled water ??
Do I even have to use distilled water, or will clean tap water work ?
A 50/50 mix of water/glycol will result in a 265 deg F boiling point..BUT the
heat transfer is no
where as good. I'm using a new 7 x gal paint can for this project, the 4 x
resistors and the welded AL
tube assy, hang from the top lid.
Thanks... Jim VE7RF
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