KB9II's QRP Dummy Load and Power Detector

Here's a simple but useful accessory for QRP operation: a dummy load - power meter. It presents a good 50-ohm 4-watt load for a transmitter while the rf detector circuit will let you measure the power into it. A regular VOM can be used to measure the dc voltage produced by the detector. I used a 1N914 diode and two 100-ohm 2-watt resistors in parallel for the 50 ohm load. Measure the detected voltage, add about 0.5 volt for diode drop, square that voltage, and divide by 100. The answer is the power into the load in watts. One watt corresponds to about 9.5 volts dc. Now you'll know whether that rig puts out one watt or two. The dummy load - power meter is fine for measuring powers above a watt or so but kind of inaccurate below 50 mw.