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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 13:39:29 -0700
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
I mean two chokes, each with five turns, wound on the same coax. There is a HUGE difference. Study k9yc.com/RFI-Ham.pdf, which includes a tutorial on how ferrite chokes work.

The chokes in series keep the same resonant frequency (and the broad resonant peak is the range where they work as chokes). Winding only one choke on two cores lowers the resonant frequency by the square root of 2, because there's twice as much L. and Fr varies as the square root of LC).

73, Jim K9YC

On Fri,4/14/2017 12:27 PM, Chuck Gooden wrote:
Jim,

Could you clarify if you mean 5 turns through each core as in separate chokes in series. Or 5 turns through both cores as in 1 choke with two cores? Or is there a difference? It doesn't seem like there would be a difference.

Chuck K9LC


On 4/14/2017 1:33 PM, Jim Brown wrote:
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.

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