RF_WATTM_ETER

Published:2009/7/8 2:11:00 Author:May | From:SeekIC

Calibration is accurate on all HF bands because circuit is not frequency-sen-sitive. Sensitivity depends on metermovement, number of turns in primary coil, and resistive voltage divider. With values shown, pots can be adjusted for full-scale values from 1-14 W. C1 and C2 are 3-20 pF. Diodes are 1N34A, 1N60, or equivalent. L1 is 46 turns No. 28 on Amidon T-50-2 toroid, with 2 turns No. 22 between ends of L1 for L2. To adjust, connect resistive dummy load to one coax receptacle and RF power source to other, with R2 at maximum resistance.Place upper switch in position providing high-est meter reading, and make that the FWD position. Switch to other position, which becomes REF, and adjust C1 for null reading. Reverse RF source and load, leaving switch at FWD, and ad-iust C2 for null. Wattmeter can now be cali-brated.—A. Weiss, ORP Low-Low Power Opert ating, CQ Jan. 1974, p 42-44 and 80.



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