Amateur Radio (G3TXQ) - Milliwatt meter

Front view of meter Inside view of meter

Every shack should have a meter capable of accurately measuring low levels of RF power. A very simple design appeared in the June 2001 edition of QST magazine in an article entitled “Simple RF Power measurement” by W7ZOI and W7PUA. It is based on an AD8307 RSSI (Received Signal Strength Indicator) chip and is capable of measuring power levels from -80dBm up to +7dBm.

This page contains a couple of photographs of my implementation of this design. Here's a link to the original QST article.

Current clamp

This is a handy “clamp on” current probe accessory for the power meter. It comprises 22 turns on a ferrite core connected to a short length of RG174 coax cable. With 22 turns on the core, when 100mA flows through the cable under test the meter reads 0dBm.