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Date: Mon, 15 May 2006 21:36:29 +0200
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From: Hans-Albrecht Haffa <dk8nd@web.de>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Transformer idea
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Dear JB,
best for transformer constructons is Jerry Sevicks Book Transmission Line =
Transformers, W2FMI  ARRL Publications.=20
1. The material o f deflection transformers for LF is a good choice.=20

2. Remove the gap of the core, replace it by a minimal gap of one layer of=
 insulation foil in each leg. This to reduce residual remanent flux from a=
bt 180 mT to abt. 30 mT

3. Look to the core as a rectangular "Toroid", at least as an UU-Core (CC-=
Core) and spread the primary and secondary over the full perimeter to have=
 no stray paths. Ore Use two halves of the pri and sec. coils for an UU-Co=
re. Or use two deflection cores as an EE-Core with rectangular cross secti=
on...

4.  the number of turns depends of the magnetic properties of the core mat=
erial, not of any AL-value.  See the basics in the catalogue of Amidon.com=
 or amidon.de. (Young Communication engineers lack the art of the calculus=
 of magnetic circuits...) I Have fed my marconi with an balun on an 61mm t=
oroid , n=3D4 50R/200R, 200 Ohm is for the antenna side.=20

5. More details upon request.=20

55, Hans-Albrecht
DK 8 ND

 -----Urspr=FCngliche Nachricht-----
> Von: rsgb=5Flf=5Fgroup@blacksheep.org
> Gesendet: 11.05.06 22:50:39
> An: <lowfer@lwca.org>
> CC: <rsgb=5Flf=5Fgroup@blacksheep.org>
> Betreff: LF: Transformer idea


> Hi Guys,
>=20
> =20
>=20
> I came up with an idea for a universal matching transformer based on inf=
ormation
>=20
> that I got from XKO's and GW4ALG's websites, and before I build it I tho=
ught I'd
>=20
> ask for your opinions and suggestions.  It's for use with a Marconi ante=
nna.
>=20
> =20
>=20
> The core is a square toroid from a TV horizontal output transformer, mea=
suring
>=20
> about 3 inches on a side and a cross section of about 1/2 inch or so.  A=
ll of the
>=20
> original windings have been removed and the two C pieces are tightly cla=
mped
>=20
> together.
>=20
> =20
>=20
> My design would have a primary wound on one side of the square consistin=
g of
>=20
> 10 turns in total, with a tap at 9 turns.  The first secondary would be =
a single
>=20
> winding of 8 turns wound directly over the primary.  The second secondar=
y is
>=20
> different in that it would be 2 quadrafilar turns wound directly over th=
e first two
>=20
> windings and connected such that there would be taps at 2, 4, 6, and 8 t=
urns.
>=20
> The two secondary windings would be connected in series aiding, so that =
the
>=20
> available taps would be 8, 10, 12, 14, and 16 turns.
>=20
> =20
>=20
> Depending on tap selection, there would be 10 different turns ratios ava=
ilable
>=20
> that would, with a 50 ohm input to the primary, give a range of output Z=
 from
>=20
> 32 to 150 ohms.
>=20
> =20
>=20
> Are there any flaws with this idea and should I go ahead and build it=3F
>=20
> =20
>=20
> 73, J.B., VE3EAR - VE3WZL
> Solar and wind powered
> EN93dr
>=20


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