250W RF Dummy Load

by E70BS
250W RF dummy load

Since I got into the HAM radio hobby, I got a need for an artificial load, also called a Dummy Load. It is basically a high-power resistor that should have the same impedance (50 Ohm) in a wide frequency range. My current rig has a power output of 100W so I targeted something like that. I purchased one RFP250N50 on eBay for around 6 Euros with shipping, but they are available at many online stores also.This is a core component of my 250W RF Dummy Load.250W Dummy Load

Technical data:

Resistance Value: 50 ohms, -+5%
Frequency Range: DC – 2.0 GHz
Power: 250W
Capacitance: 3.3 pF

250W Dummy Load RF Characteristic

We can see on this graf that Impedance is almost flat on HF, VHF, and UHF frequencies, so this is a perfect candidate for a dummy load.

Making the Dummy Load

Making it was an easy one-afternoon job. As this little thing mostly converts RF power to heat, what is needed is a good old heatsink. I used two AMD CPU heatsinks and they are doing an excellent job. The rest of the parts are one female PL259 connector, 4 distancers for the computer mainboard, and some thermal paste. Most of the job was drilling and milling, and here is how it was done.

If you like this article maybe you would be interested in this one about making a HAM radio PSU also.

Thank you for reading and if you have any questions regarding this DIY, please leave a comment.



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