[ARC5] ARC-5 transmitter frequency drift suggestion

[Neil]

Frequency drift in the ARC-5 and SCR-274N transmitters can be mostly
attributed to the 1626 oscillator being run at high power level in order to
supply adequate drive to the 1625 grids.

It occurred to me some time ago that if the 1625's were to be run in Class
AB1 instead of Class C, the drive power required would fall to virtually
zero. This could be easily done by lifting the grounded end of the 1625
grid resistor (15K) and feeding -35V bias to it.

The 1626 would now be required to supply a maximum of 35 volts of drive
(at virtually no power), versus the previous 100 volts or so at about 7mA
(half a watt). Its plate voltage could be scaled back accordingly, to perhaps
150 or even 105 VDC regulated.

I'm sure this would work very well in the case of CW, but I can't recall
anything in the literature describing AM plate modulation of a Class AB1
power amplifier. Has anyone tried this or can point to literature on the
subject?

73 de Neil ZL1ANM
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