Quick and easy marker generator
by sv3ora

This marker generator has been designed so that it can be used as an analogue dial calibrator. Most analogue dial transceivers have 100KHz or in the best case 25KHz marker spacings, but my calibrator has 100KHz and 10KHz, which increases the calibration accuracy a lot.

The goal was to make a quick and easy calibrator using one chip and a few features without increasing complexity. A battery is used as a PSU and a blinking led allows for pulsating operation of the marker, so as to make the marker frequencies distinguishable from other band tones. A single DPDT ON-OFF-ON switch takes care of the power to the calibrator, the selection of the marker frequency and the disconnection of the antenna when the marker is switched off, so as to protect the calibrator from burning out on accidental TX from the transceiver.

Calibration is done with a modern digital HF transceiver. Switch to the highest HF band and pick up a marker at some 10KHz or 100KHz point. Then adjust the variable capacitor to zero beat to the marker frequency. Adjustment is better done using headphones, so as to be able to listen to the very low audio frequency tone close to the zero beat point.

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