Here's a simple instrument for the homebrewer to measure RF power well through VHF. interests. The reference instrument incorporated a built-in analog meter and provision to connect an external DVM. It also utilized a conversion chart to relatemeter readings to RF power.
The DVM (Digital Volt Meter) also displays the correct polarity sign. There’s neither rocket science nor smoke and mirrors here folks: It’s all done simply with op amps and resistors! The schematic tells all.
In the process of designing these basic of power meter circuit functions, it occurred to me that other simple additions would add a lot to the utility of the instrument. Thus, the project grew “on the fly.” One of these extras is a gain-change option that includes an external OFFSET control for the analog display.
For more information about component parts list, power meter process design, and calibration-operation, please download An Advanced VHF Wattmeter (in Pdf).
Source: RF power meter project by Wes Hayward, W7ZOI and Bob Larkin, K7PUA that appears in QST, June 2001.
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