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Message-ID: <B3C08CB88D994D7DA3369EDED7EFB875@JimPC>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
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Date: Sun, 20 Feb 2011 20:53:14 -0000
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Subject: Re: LF: toroid xformer
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Dear Hans Albrecht, Mal, LF Group,

A better alternative to mains transformers, etc., is to use one of the 
larger sizes of ferrite SMPS core sets. That way, you can design a 
transformer to produce the required impedance ratio for your PA, antenna and 
loading coil, instead of trying to do the design backwards by starting with 
the transformer. You need a large core compared to LF/MF to get a reasonable 
inductance, flux density and size of wire. I made a matching transformer a 
while ago that works quite happily at the 100W level at 9kHz using an ETD49 
core set. I think an ETD59 core set would be OK for at least a few hundred 
watts. These things are available fairly cheaply from suppliers such as RS 
Components and Farnell in the UK.

Cheers, Jim Moritz
73 de M0BMU