[Elecraft] OT: Effect of Compression and Expansion on theInductance of Toroids?

[W3FPR - Don Wilhelm]

Darrell,

There may be a small apparent change in inductance when adjusting the turns
spacing of a toroid, but it would only be a small percentage - look at the
formulas for a toroid inductor to verify that fact - there is no term for
the turns spacing, and the diameter of the toroid fixes the coil length.
Check out http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/indtor.html
for the detailed formulas.

If you move all the turns to one side of the toroid core, it may begin to
behave more like a solenoidal inductor and the inductance could possibly
change because the effective length of the solenoidal inductor will change,
but I have not persued that 'angle'.  Elecraft usually specifies that the
winding should occupy about 85% of the core, so that 'fixes' the length of
the coil question for a properly wound Elecraft toroid.

The inter-turn capacity is bound to change with the turns spacing, and that
may show up as an apparent change in 'inductance' on many meters because
they do measure inductance at a specific frequency.  The best way I can
think of to prove or disprove it would be to measure the time constant in an
LR series circuit.

73,
Don W3FPR

> -----Original Message-----
>
> Well, it seems now that I am receiving contradictory information.
> Specifically
> that compressing the turns on a toroid will raise the inductance.
>
> What is the real scoop. Does compressing or expanding the spacing of the
> winding on a toroid change the inductance? Or just the distributed
> capacitance of the toroid? Or is this much more complex than I would have
> expected?
>
>
--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.344 / Virus Database: 267.10.16/83 - Release Date: 8/26/2005