Progress with the "Huff and Puff" stabiliser

The stabiliser is now installed on the same breadboard as the "Ugly VFO" and I have connected the two. The RF input to the stabiliser comes straight from the VFO output buffer amplifier. The stabiliser control output drives a varactor circuit (as per the X-Lock manual) that is connected in parallel with the tuned circuit of the VFO. An LED is used as the varactor. Here is the revised circuit diagram.


The first tests of the stabiliser and VFO saw the status LED flashing green / red, suggesting high VFO drift. Listening to the VFO on my FT-847, however, it didn't sound like it was drifting that badly. I adjusted the variable resistor that controls the level of RF input to the stabiliser; setting it to mid position gave me a steady green LED, indicating lock.

I can hear the VFO drifting very slowly up and down by a small amount, so the stabiliser seems to be controlling the VFO. But I want to do more testing before I'm happy that I am using the stabiliser properly.