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Re: Topband: [time-nuts] Minicircuits 10% discount in December

To: topband@contesting.com
Subject: Re: Topband: [time-nuts] Minicircuits 10% discount in December
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Thu, 27 Nov 2014 13:10:45 -0800
List-post: <topband@contesting.com">mailto:topband@contesting.com>
On Thu,11/27/2014 11:14 AM, Tim Shoppa wrote:
The 2873000202 73 material binocular core, I buy those by the hundreds from
Newark and hand them out like a human Pez dispenser at local radio club
meetings. They are amazing things. Not only do I use them for 160M and
other RF applications, but I have using them in small step-up applications
too up to the 10W level!!!

The single turn resonance of this core is around 10 MHz, with a Z at resonance of about 120 ohms. Like any other ferrite core, winding turns will increase L as N squared, increase C as N, thus moving the resonance down in frequency. I'd guess that 8 turns would move the resonance fairly close to 160M with Z in the range of 4-5K ohms. The catch is that the i.d. is pretty small, so the choke would need to be wound with something like one pair out of CAT5 cable.

Fair-Rite considers this a suppression part, not an inductive part, although it is widely used for winding transformers for MF RX antennas. The laws of physics don't change with what we call something, so this will be a fairly lossy transformer. For RX transformers, it may not matter (and the low Q may even help), but don't be surprised when you see the added resistance beyond what the turns ratio predicts. :)

73, Jim K9YC
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