AUDIBLE_TUNING_FOR_BLIND

Published:2009/7/3 3:51:00 Author:May | From:SeekIC

Transmitter or exciter output is sampled at coax line and highresistance voltage divider. Rectified voltage of divider, which varies during transmitter tuning, is fed to relaxation oscillator whose output varies in pitch with voltage; low voltage gives high-pitched tone, and high voltage gives lowpitched tone. Input divider draws about 1 W from 100-W transmitter; for higher power, such as 1 kW, change 10K to about 100K. Diode feeds about 2 V to emitter of transistor. Any audiotype PNP transistor can be used. For NPN device, reverse diode connections. Transformer is from 5-W transistor amplifier, with 22-ohm high-impedance winding. Other two windings, in series aiding, are 4 ohms each.-D.H. Atkins, Tuning Aid for the Sightless, Ham Radio, Sept.1976, p 83



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