[GreenKeys] Heath HG-10 VFO with FSK modification

[Roy Morgan]

My Heath HG-10 is out of storage for restoration. It has both a small AC supply built in (good), and what appears to be a circuit to FSK modulate the oscillator (May not be useful).

As I remember, it would switch a teensy bit of of capacitance on and off in parallel with the VFO tank circuit to shift the VFO frequency. There is a 2.5 mH choke, a diode, resistors and caps. (The terminal-strip mounted thing is disconnected from the rest of the VFO.)

Can anyone point me to the details of this early FSK modification?

(I expect to do real audio FSK with the Dovetron and Kenwood 440 and 940 transceivers in SSB mode, though they do have switching level TTY inputs that would work. )

Roy Morgan
K1LKY Western Mass
K1LKY68 at gmail.com