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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  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.


    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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