On Tue, 16 Dec 2008 03:56:41 -0500, Roger W. Macdonald wrote:
>As to Jim's comment about #31 material being better, I have not
>been able to find #31 material except in the "cable clamp"
form,
>not the core form like the type 43 material.
See Appendix One of http://audiosystemsgroup.com/RFI-Ham.pdf
The cable clamp form would also work fine if it's big enough to
accomodate the required number of turns. Again, see data in the
tutorial. Note that the data in the tutorial is MEASURED!
The current version of the Fair-Rite catalog (nearly two years
old), is in pdf form on their website. It lists #31 as the
material of choice for HF suppression, partially, I suspect, on
the basis of my published work. I first published my work three
years ago, and have significantly expanded it in the last year
or two. When I began my research and acquired samples from Fair-
Rite (about five years ago), #31 was a new material and used
only for a few parts. They were not yet making toroids. But I
requested samples, and a few months later received five of the
2.4-inch o.d. toroids.
Most ferrite parts sold by stores like Amidon, Palomar, DX
Engineering, the Wireman, and others who advertise to hams are
actually made by Fair-Rite, a very good US company. Fair-Rite
has at least a half dozen US distributors, and many more
worldwide. They are industrial distributors, like Newark,
Allied, Kreger, etc., so you get significant discount if you buy
quantity.
Sadly, the stores that advertise to hams are NOT engineers, they
are SALESMEN, and they do not keep up with what's going on. This
becomes obvious when they don't sell or stock #31 parts.
Appendix One of my tutorial lists several vendors who DO sell #
31 material, and talks about how to buy from them.
73,
Jim Brown K9YC
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