VFO Stabilizer Source Code & Links
The following are source codes for the EI9GQ VFO Stabilizer and are based on his design. My modifications were to change the source code for more common IF Frequencies and with the Help of Ron, G4GXO were ported over to the more advanced and less expensive PIC 16F628.
My expereince with these stabilizers has been outstanding! They work well and in the case of one VFO have held the frequency constant within 10 hertz for close to 24 hours. You will see references to Huff and Puff. This is basically how the circuit works --the frequency output of the VFO is constantly measured and voltage corrections are generated and fed to a voltage variable capacitor. The magnitude of the voltage is dependent on whether the frequency is changing in a + or - direction. The only short coming is that the frequency must be manually locked each time you change frequency. Not a big deal!
  8.0 MHz IF & PIC 16F84   8.0 MHz IF PIC16F84.asm  
  9.0 MHz IF & PIC 16F84   9.0 MHz IF PIC16F84.asm  

9.0 MHz IF & PIC 16F628

  9.0 MHz IF PIC16F628.asm  
  VFO Stabilizer Built by W6JFR   EI9GQ VFO Stabilizer