100W dummy load

	THE PROJECT This was a project to make a dummy load or, as the finished thing is more correctly labelled, a fifty ohm resistive load.
	The project began with a heat sink. I have done without a permanent dummy load, making any necessary resistive loads as and when I've needed them. But having a heat sink to hand it seemed only right to make something that needed to dissipate heat!		I wanted to make the load as small as possible, so that meant finding a suitable box that would match the heat sink. The heat sink's footprint is 70mm by 37.5mm so a Maplin's two-piece aluminium case type AB12 is just about right (76x51x25mm)
	I decided that, rather than go for a single 259 connector, I'd include a SO-239, a BNC and a Phono socket and avoid needing to make patch leads. BI TECHNOLOGIES' MHP 100 RESISTORS These resistors are impressive beasts, rated at 100 watts each. The BI Technologies TO-247 resistors are rated at 100W with a heatsink (and a measly 3W in free air) so two in parallel - together with adequate heat dissipation - should really provide fifty ohms for a 200W transmitter. (It happens that I don't own a transmitter that can manage more than half of that, anyway!) As the heat sink I used is rated at 4.1C/W the completed load will handle 100W for a good half a minute (maybe a little longer) without undue stress on the components - It's warm after thirty seconds at 100W but not too hot to touch! But the bottom line is this: It benefits from being able to withstand well over the 100W target for the project.
			The resistors are made in TO-247 packages with a metal plate on one side to aid conduction to a heat sink. I used two 100 ohm resistors back to back (with their leads twisted and soldered) to give the notional fifty ohms which, when checked with a multimeter, measured 49.9 ohms.
	The only real downside to using these resistors is their being a fiver each (Well, a bit less, so that's alright then!) I got mine from Farnell (http://uk.farnell.com, part number 1114421 where they are described as RESISTOR, 100 OHM 1% 100W TO-247)