Toroid core material

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "J. B. Weazle McCreath by way of Terry Fritz <teslalist-at-qwest-dot-net>" <weazle-at-hurontel.on.ca>


Hello Coilers,

I've some info and a question for my fellow coilers regarding various
materials used in making toroid cores and their usefulness as chokes
in TC service.

As an RF filter in the hot lead of my PDT was a three turn choke that
I'd wound on a toroid core removed from an old computer power supply.
After a minute or so run time of the coil, the core material was hot
to the point of being uncomfortable to hold onto.  This indicated it
was pretty lossy, so I tried another core which had started life as
an 88 mH. "telephone choke coil" and noticed no heating even after
several minutes run time of the coil.

It would seem that we need to choose the core material carefully for
this type of use.  The big question is, what is the core material of
the computer PS toroid and of the 88 mH. toroid?  They are obviously
quite different in composition, no doubt due to the frequencies they
where chosen to work at in their original uses.  I suspect that the
computer toroid worked in the 10's of kHz. range while the telephone
one likely was for voice frequencies of less than 3 kHz.

73, Weazle, VE3EAR/VE3WZL

Details of my "Hyperbaric Gap" and Tesla coil are at:
http://www.hurontel.on.ca/~weazle