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Re: [RFI] New Larger Fair-Rite #31 Toroid

To: rfi@contesting.com
Subject: Re: [RFI] New Larger Fair-Rite #31 Toroid
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Fri, 14 Apr 2017 11:33:13 -0700
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On Fri,4/14/2017 10:26 AM, Dave Cole wrote:

A question for you... Looking at the "Impedance vs. Frequency vs. Turn count" graph at:


It looks like these new cores only have two or three K of impedance with five turns... Am I interpreting this correctly?


If so, then using two of them with five turns becomes the standard if I want more than five K impedance? Is that true?

The number of turns (and to to the extent that it affects capacitance, wire size and spacing) sets the resonant frequency. The Fair-Rite data is most likely for small diameter wire. If you want the choke to be effective where 5 turns puts it, yes, two chokes in series would be the way to get there. A choke wound with RG8/11 size coax would have the same inductance but more capacitance between windings if those windings are closely spaced, so the resonance would be a bit lower.

And, of course, more turns will lower the resonance even more, and because R also increases with N-squared, also raise the impedance.

73, Jim K9YC

73s and thanks,

On 04/14/2017 09:53 AM, Jim Brown wrote:
Yesterday, I got a quote on this part from Dexter, a vendor that has
been competitive for past orders. They don't have stock, minimum order
is a full box, which is 25 pieces, $15.18 each. 50 pieces is $14.27
(-6%). 100 pieces is $13.57. Delivery was quoted as 14 weeks.

73, Jim K9YC
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