02μW_TO_10_mW

Published:2009/6/26 4:00:00 Author:May | From:SeekIC

Accurate low-power wattmeter uses small lamps as barretters for measuring RF power up to 10mW from 1 to 500MHz. Applications indude measurements of antenna gain, local oscillator frequency, VSWR, and filter response. Subminiature T-3/4 RF sensor lamps operate in bridge circuit with R1, B2, and R3. Voltage difference between bridge legs is amplified by opamp U1. Bridge current driver Q1 supplies current for balancing bridge. Equilibrium voltage of 3.5 V at VB is fed to metering circuit including U2. Article covers calculation of values for calibration resistors R4-R10, which range from 5.715 to 7192 ohms.-J. H. Bowen, Accurate Low Power RF Wattmeter for High Fre-quency and VHF Measurements, Ham Radio, Dec. 1977, p 38-43.



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