Dummy Load

I wanted a simple dry dummy load for testing and to tinker that's capable to take a decent amount of power from the transmitter. This was a quick little evening project once I picked out and received the parts.

Parts:

• Heatsink Wakefield 423K 140x120x67mm
• 50 Ohm 250N50 Resistor
• Type N Female Panel Mount
• Thermal Paste
• 3x screws and nuts

Total cost was about $47 dollars for two dummy load. I only build one so far. The heatsink is the most expensive part by far.

Construction:

The construction was quite easy. I opted to share a screw with the resistor and coax connector for simplicity and ease of ground connection.

Results:

The SWR of the dummy load is perfect for HF and quite good for higher frequencies.

SWR plot:


Impedance plot:


AntScope file: dummy-load.antdata
AntScope2 file: dummy-load.asd
(AntScope can be downloaded at the RigExpert website for free.)

So far I have used the dummy load with a Boafeng on 2m and 70cm using 5W and Icom 7300 at 30% power using SSB on 20m band. I haven't noticed any increased temperature of the resistor.

Potential enhancement:

• Adding a wattmeter circuit would be nice.
• RF shielding on the bottom