A Resistive UHF Dummy Load

A very simple and effective dummy load can be made from several resistors, a connector, and a small metal plate or piece of PC board stock. Use six 1/4 or 1/2 watt carbon resistors whose paralled value equals 50 ohms. These should be CARBON only, not metal film. Six 300 ohm resistors will give 50 ohms, or you can use 270 ohms or 330 ohms (Will give 45 or 55 ohms respectively). Using three 270 and three 330 ohm resistors alternatively will yield 49.5 ohms and this is within 1 percent of 50 ohms. The allowable dissipation will be higher if a metal plate is used as it will act as a heat sink. Keep leads very short, preferably as close to zero in length as possible. If you can find some, Allen Bradley style RC07 carbon composition are ideal as these look fairly resistive well into the UHF spectrum. Alternatively chip resistors can be used and these are excellent, albeit somewhat difficult to handle mechanically.