Building a Dummy Load

If you plan to transmit on your radio, you need a way to test your transmitter without radiating a signal. You do that by transmitting into a “dummy load”. I had a 20 Watt dummy load, but I needed one to handle 100 Watts, so I built a $40 kit in June. This was the first serious soldering I had done in years, maybe decades.

I built the Oak Hills Research RFL-100 kit. A pre-built 100 W dummy load is usually $150-200. This kit is $40.

The dummy load is twenty 5 W resistors in parallel. Here are the first two resistors, ready to be soldered.

Dummy load 1

And here we are, with half of the resistors soldered onto the board.

Dummy load 2

Here we see all the resistors soldered, the board installed in the nice enclosure, and soldered to the the input connector. I chose a BNC connector instead of the standard UHF connector. My ham shack is cabled with BNC. The enclosure is marked up under the connector mounting nuts because I ground off the paint with a Dremel tool. That was much easier than sanding the paint off.

Dummy load 3

Is it 50 Ω? Well, let’s see. Hmm 49.9 Ω is within 0.1%. My Ohmmeter is accurate to +/-0.5%, so I’ll take that as a solid 50 Ω.

Dummy load 4

Finally, let’s connect it to my new 100 Watt power amplifier on the ANT 2 port. Looks great, handling 100 Watts continuous with a 1:1 SWR.

Dummy load 5

If you have a transmitter and need a dummy load, I highly recommend building the Oak Hills Research RFL-100.