Re: VFO Stability

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From: David D. Meacham (ddm@datatamers.com)
Date: Tue Aug 08 1995 - 16:11:18 EDT


John,
The -7 material IS a lot better than the others, but it turns out that it
is very sensitive to stray magnetic fields, too! Anything magnetic near
the rig can cause VFO frequency shift. There was even a report of shift
when mobile and driving under a steel bridge! 72, Dave, W6EMD
---------------------------------------

On Mon, 7 Aug 1995, John Seboldt wrote:

> Clark Fishman <cfishman@fsac3.pica.army.mil> recommended -7 core material
> to help stability in VFOs. I have heard of this, but the last Amidon
> flyer I got with an order (about 3 months ago) had nothing to say about
> them, though it was listed on the enclosed price list. Something to try.
>
> 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.
>
> : John Seboldt rohrwerk@netcom.com / CW: It don't mean a thing
> : Amateur radio K0JD... / if it ain't got that swing!
> : Church of the Annunciation, / Di dah, di dah, di dah, di dah...
> : Minneapolis / (sorry, Duke!)
>
>
>


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