[Hallicrafters] HT-30 or adventures with a heterodyne vfo

[David Thompson]

Collins and Eldico used a PTO for stability on CW and SSB.  hallicrafters
adopted a technique which had been around since before WW II called the
heterodyne method for the VFO in the HT-30 low power SSB/CW exciter
transmitter. Curca 1955.

Most of us understand the heterodyne method but this makes excellent sense
for the CW operator as applied to the HT-30 by Hallicrafters.  The usual
method of doubling for frequency multiplication is replaced by the hetrodune
method.  In the HT-30  the crystal oscillator and VFO operates far outside
any ham band.  Keying is done in the mixer and amplifier  Since the
oscillators run all the time this means that frequency stability is very
good.  This also eliminates the possibility of chirp as there is no starting
and stopping of an oscillator.

Hallicrafters published a white paper or shaping the keying characteristics
as you wanted.

This from an old national Traffic CW man who never owned a mic.

The problem with the later Hallicrafters HA-5 stand alone VFO was you needed
to apply the HT-30 keying technique.

73 Dave K4JRB