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.

"Huff and Puff" stabiliser is underway

After a (too) long break from the workbench, I have now assembled and tested the "huff and puff" VFO stabiliser from Cumbria Designs. The plan is to use it with the "ugly VFO" that I built earlier in the year.

The instructions were very clear and the stabiliser went together quickly. Ron Taylor G4GXO from Cumbria Designs had kindly sent me the latest software for the PIC that controls the stabiliser.

The stabiliser indicates its status through a tri-colour LED, so it is possible to unit test it after assembly, making sure it powers up correctly and that it can "see" an RF source when you connect one to its input. I hooked up the stabiliser temporarily to the "ugly VFO" and the LED showed steady red, a good sign.

The stabiliser controls the VFO frequency through a variable capacitor circuit that you add to your VFO. So next steps for me are to install the components for this on the VFO breadboard, mount the stabiliser next to the VFO, hook them together and see what happens.

Photo © Cumbria Designs