Re: VFO Stability


From: Mark J. Dulcey (
Date: Tue Aug 08 1995 - 00:47:06 EDT

On Mon, 7 Aug 1995, John Seboldt wrote:

> Meanwhile, the basic consensus is that ANY core material is a
> compromise for VFO use. An air core coil is by far the most stable
> inductor to use. The traditional ceramic form is most recommended, with
> glass tubing and acrylic rod also getting some nods. Toroids have become
> popular for compactness, of course, but unless that -7 material is really
> good, air core is still the ultimate if you make room for it.

This is true for rigs intended for use while standing still. Air-core
inductors, especially the large ones needed for HF use, might present a
problem with mechanical stability in mobile and hand-held gear, though,
resulting in a drift cure that is worse than the disease of core
instability. The best bet there, of course, is a frequency synthesizer,
but a well-built ceramic or even powdered-metal toroidal core is likely to
be a better bet than air-core.

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