Jim and all...
What I am looking for is a small donut core from Fair-Rite, something akin
to the size of an Amidon FT-50 core.
I'll admit that maybe it's me, but I cannot find any #31 material from
Fair-Rite in anything but (1) clamp-on, (2) elongated cores for cables, and
(3) large diameter donut cores. If anyone has a specific core model number
or catalog page number, I would really appreciate it.
Paul, W9AC
. .
----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: "RFI List" <rfi@contesting.com>
Sent: Sunday, January 11, 2009 10:06 PM
Subject: Re: [RFI] Fair Rite #31 Mix Material
> On Sun, 11 Jan 2009 21:01:39 -0500, Paul Christensen wrote:
>
>>Anyone know a source of small toroid donut cores in #31 material?
>>Do they even exist?
>
> Of course. Fair-Rite INVENTED the #31 mix about five years ago.
> Since then, they have expanded and re-shaped their product line to
> build nearly HF suppression components in nearly all common form
> factors using #31 material. The link below is to their on-line
> catalog. I don't know of any other mfrs who have duplicated the #31
> mix yet.
>
> http://www.fair-rite.com/cgibin/catalog.pgm#select:where4
>
> Fair-Rite is THE mfr of the vast majority of ferrite parts sold to
> hams. Vendors like Amidon, Palomar, the Wireman, and DX Engineering
> buy these parts, create new part numbers for them, and resell them,
> mostly at obscene markups (4X-5X is typical). Not only that,
> they're selling obsolete parts -- mixes that are relatively poor
> choices for HF suppression.
>
> It is EASY to do business with Fair-Rite and their distributors.
> Appendix One of my RFI tutorial lists a select handful of ferrite
> parts that are quite useful to solve HF noise and RFI issues. It
> also lists a half dozen very good industrial vendors who sell these
> products in quantity at very good prices.
>
> Anyone who organizes a group purchase in the 1,000-lot range can
> buy #31 2.4-inch o.d. toroids for about $4, tax and shipping
> included. The 1-inch i.d. "biggest clamp-on" sells for about $12 in
> lots of 250 or so, and is electrically equivalent to three of the
> toroids. When I lived in Chicago I helped organize a group purchase
> that included a bunch of the SMC guys and the North Shore Radio
> Club. We also had participation from the MPLS area and downstate
> IL. That appendix includes a worksheet to help you decide how many
> of what parts to order.
>
> A year ago, we did a very large group purchase for the Northern CA
> Contest Club (SF Bay area). This past summer I helped ND2T fix RFI
> in his neighbor's A/V rig. Tom transmitted on each band while I sat
> with the neighbor and figured out the coupling mechanisms involved.
> Tom pulled a half dozen big clamp-ons out of his stash, we threw
> them on the loudspeaker cables, and the RFI went away. Tom was
> prepared, so it was easy. I had already prepared the neighbor for
> paying them them, but Tom decided to make a gift of the ferrites to
> his neighbor.
>
> The tutorial is http://audiosystemsgroup.com/RFI-Ham.pdf
>
> The Chicago group purchase was about 4 years ago. I wouldn't be
> surprised if you could do another one by now. I'd start by
> contacting W9DXCC, SMC, the North Shore club, and the contest club
> in MPLS.
>
> 73,
>
> Jim Brown K9YC
>
>
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