Greybeards (Re: Netbooks & BSD)
gull at gull.us
Fri Oct 22 17:09:27 UTC 2010
On Thu, Oct 21, 2010 at 6:32 AM, Arthur Chance <freebsd at qeng-ho.org> wrote:
> Dredging up physics unused for 30+ years, ferrite is ferromagnetic and
> intensifies magnetic fields so a coil of wire with ferrite inside is a
> massively bigger inductor then an empty coil. I vaguely remember that brass
> is slightly diamagnetic, but could be mistaken.
A ferrite slug increases the inductance of a coil, relative to an air
core; a brass slug decreases it.
I've got a homebrew amateur radio transceiver that uses a coil with a
brass machine screw in it for tuning. Wind the screw out of the coil,
inductance goes up. A cheap and simple form of permeability-tuned
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