[Elecraft] Dummy load

Fri Nov 8 22:36:40 2002

Hi

Carbon comp resistors are getting scarce especially the 2 watt type but you
can use MOS resistors. They are non inductive and more accurate than the
carbon comp resistors. They are available in 1, 2, 3 and 5 watt sizes.
Something else you may want to consider for a dummy load are the Ohmite
TO-220 resistors. These resistors are in the the same package as a TO-220
transistor and are rated at 35 watts when mounted to a heatsink of the
proper size. You could mount 3 150 ohm resistors to a heatsink and wire them
in parallel for over 100 watts They are about $6 each.

Don Brown
KD5NDB

----- Original Message -----
From: "Jeremiah J McCarthy" <[email protected]>
To: <[email protected]>
Sent: Thursday, November 07, 2002 10:56 PM
Subject: [Elecraft] Dummy load

> Popular Electronics published an article in 1970 on how to build a dummy
> load into a paint can ala the Heathkit Cantenna...Very simply it
> consisted of 2 large copper washers, a short length of 1/2" copper pipe,
> and ten 510 ohm, 2 watt composition resistors soldered in parallel
> between the two copper washers, which were drilled to accept the resistor
> leads...A PL-259 was mounted in the center of the paint can lid and the
> pipe/washer/resistor assembly was soldered to and suspended from the
> bottom the PL-259...This assembly was immersed in transformer or mineral
> oil in the can, raising the power handling from 20 watts to 200 watts...I
> built one of these and still use it, although I made mine with twenty
> 1000 ohm resistors, making it capable of 400 watts...In those days I was
> running Drake Twins, rated at 200 watts PEP, and never heated the oil...
>
> I recently saw a variety of 2 watt composition resistors at a flea
> market...
>
> Jerry, wa2dkg
> K2 #2549
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