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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