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Message-ID: <3.0.5.32.20010611120331.00891a90@pop3.esoterica.pt>
Date: Mon, 11 Jun 2001 12:03:31 +0000
To: rsgb_lf_group@blacksheep.org
From: "Brian Rogerson" <brian@esoterica.pt>
Subject: Re: LF: [TECH] Help needed on toroid trasf. construction
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May I add a request please, I am looking for the design of an "ultimate"
3dB splitter for 136KHz with good characteristics to well down below
72KHz.

73, Brian

At 13:34 11/06/01 +0200, you wrote:
>Hi all,
>  I need some words of wisdom and a bit of help about the
>construction of a small toroid transformer.
>
>First the antefact : I swapped recently my TS-850 for a TS-950SDX,
>a very fine radio, but much less sensitive on the LF band than the TS-850.
>Looking at the schematics, and doing some filter simulation with
>Electronic Workbench, I think to have found the culprit, i.e. L3, a small
>toroidal transfomer, with ratio 1:4, which is inserted in the signal path,
>after the input attenuator, and before the filters bank. With all
probability,
>its  response at 136kHz leaves much to be desired. The TS-850 doesn't
>have any such transformer, the signal goes straight to the filters.
>
>So I have decided to replace it. Looking in the MiniCircuits catalog, I have
>found what seems to be the ideal replacement, the T4-6T-KK81 model, which
>has a -3dB response from 10kHz to 100MHz. Problem is that this transformer
>is not carried in stock by the Italian distributor, and both they and the
>MiniCircuits sales office have a minimum quantity amount for an order.
>
>At this point the only choice is to build it myself. And this is were your
help could
>come in my rescue. I need to know what your experiences are in building
>such a wideband kind of transformers. What is the best type of material,
>caveats to not forget, optimal number of turns, you name it.
>
>TNX for any help,
>
>73  Alberto  I2PHD
>
>
>
>
>
73 Brian     CT1DRP     IN51QD     41 09 58N  08 39 11W
http://homepage.esoterica.pt/~brian