YO3BN - 2GHz 250W 50 Ohms Dummy Load

Posted at - 9th August 2017
Edited at - 13th August 2017

2GHz 250W Dummy Load

Recently, I have been working on a 50 Watt QRO for 80m band and my old dummy load failed to handle that power, getting red hot into several seconds. Finally I've finished my high power dummy load. The components were purchased two years ago but I had no motivation to put them altogether until now. There's nothing special with this dummy load, just a power 50 ohm resistor placed on a ALU heat sink. With proper cooling system (fan placed nearby) it can handle 200-300W CW.

The heart of this dummy load is the RF designed 50 ohm resistor rated with 250W power dissipation from DC to 2GHz, model CHF9838CNF500L from Bourns, so it's not a chinese cheap one. The N connector also is high quality rated for 11GHz from Amphenol.

Construction Details

The resistor was locked in place with two M3 screws and CPU thermal paste applied underneath.

A little flaw I did was to place the resistor too close of heat sink edge, but is not a real big problem, at least for 50W.

My old dummy loads in pic down below. They were made by 20 pieces of 3W 1kohm resistor in parallel. 60W max, no cooling system.

Testing

I tested it with 50W CW for more than 5 minutes and it became hot, therefore a fan was used to cool it down.

73 de YO3BN