"Stan Barr" wrote


Back in 1977 there was a circuit published widely that claimed to
correct drift in a vfo by sampling the output, downconverting it,
comparing it with a crystal oscillator then correcting a varicap in
the vfo. Has anyone ever tried this? How well did it work? This
circuit, if it works, could be resurrected and bring a lot of the
older Boatanchor Rigs back on the air. It was called an FLL or
Frequency Locked Loop and was not very complicated.

Known colloquially as a "Huff and Puff" stabilizer of which PA0KSBs
one is an improved version. There was a simplified version of
PA0KSBs circuit published by G3DXZ, and a faster one by G7IXH.
They were discussed at length in the Radio Society of Great Britains
magazine "Radcom" in 1996 and 97, but that's probably not much help
to you. I believe that G7IXHs version was published in QEX in 1998
if that helps.



**** Hewlett Packard used this principle with the HP8708A Synchroniser
which was used with the HP 606B and HP608F signal generators.It would
lock them down to a very small frequency range.

Brian Goldsmith.