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Topband: impedance transformer windings

To: <topband@contesting.com>
Subject: Topband: impedance transformer windings
From: "Steve Flood" <flood@ixi.net>
Date: Mon, 27 Oct 2003 14:04:27 -0700
List-post: <mailto:topband@contesting.com>
I've been trying to put together an impedance transformer on the Amidon 
BM-73-202 binocular core.  It is to be used on a flag RX antenna for 160m so I 
need about a 950:50 (19:1) transformation.  The published AL is 8500 mH/1000 
turns.  This translates to 8.5 mH per turn.  From a Handbook formula, I 
calculated I need 1.4365 mH on the HI Z side and 0.0765 mH on the Lo - Z  side. 
 As you can see, even one turn thru the core exceeds these by a large margin.  
Do I need a core with a lower AL?  Seems like many folks recommend the 
BN-73-202 though with a 3:12  (W7IUV) or 1:4 (W8JI) turns.   But I can't arrive 
at these numbers by equation.  I'd like to learn how this works rather than 
just build it without learning.

  Thanks all.  Steve KK7UV.
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