Homebrew dummy load

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A simple DIY dummy load project from Flathagen:

I have created a simple 50 Ω dummy load to test transmitters. I also added a simple RF diode detector so I can measure the peak voltage, and calculate the power.
The dummy load consists of eight 100 Ω resistors rated at 2 W so the load should handle 16 W, at least for short periods. I constructed the dummy load using a combination of ugly construction and Manhattan style, by gluing pieces of PCB (as isolation pads) on top of a ground plane PCB. Then I soldered the components directly on the copper without drilling holes.

Project info at DIYcrap.

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3 Comments

  1. Since it’s only a few extra parts, I find it worthwhile to add a diode and a capacitor to measure peak output power.

    The diode allowed the cap to charge and retain a voltage by rectifying the AC signal, If you add back the loss of the diode and do some simple calculations you can get the power output.

    http://www.k4eaa.com/dummy.html

    www (dot) ai4ji (dot) com/Projects/dummyload.htm <– trying to stay out of the spam filter from too many URLs in a message

    It took me a while to figure out why they're putting the cap outside the can. I think it's so you may remove it and observe the waveform on an o-scope.

    1. D’oh! The URLs explain how to do the calculations well, and I wanted to explain why the cap is made removable. Obviously you added the diode and cap to the circuit already.

  2. At what frequencies are you going to use it? I guess you don’t have to reach GHz before it will deviate from 50ohm due to the way it’s built.

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