If anybody is interested in using Loftur's excellent loop tuner to automatically control the varactor tuning voltage on Rick Karlquist's (N6RK) also excellent tunable shielded loop antenna, it is easy to do. Just add the following lines at the very end on the ML_Pos_Mgmnt file before the last curly brace:
int varactor = map(stepper_track[ant], min_preset[ant].Pos, max_preset[ant].Pos, 0,4095); // Scale varactor voltage
analogWrite(A14, varactor); // Output varactor voltage on DAC output pin
You may want to use a linear optocoupler to isolate and also scale the teensy DAC output voltage to the range your varactor diodes use. Now go ahead and teach the tuning positions as usual.