I have been writing in good old
VB6.0 stepper motor software
with very easy and cheap to build hardware
running on a PC with LPT port.
My software runs already on a old Win98 PC.
The stepper can drive a Magnetic Loop Varco
Locked on the cat control of a FT817 or FT840
So just turn the dial knob of the rig and the loop wil be
locked on frequency through a table with
various interpolling methodes.
So enjoy and take a look at my free software
All circuits diagrams are in the program under
Very nice is the option to control the stepper
with the mouse scroll wheel and grafic interface.
Of cource you can use the program for other purposes
like turning a webcam or adjusting the volume control
of a AF ampliflier