Tom, I have the book. Sevick seems to use 250 permeability cores for the
baluns. I assume he needs to match 50 ohm coax to a balanced 22 ohm load.
There are numerous designs in the book to do that job. Most use one core to
do the balun job and another to do the Z transformation but one design uses
a single core with 2 windings on it. One is 6 turns tri-filar of nr 14 H
Thermaleze interconnected. The other winding is 6 turns of a home made low Z
coax. This uses nr 12H thermaleze for the center conductor covered with
Teflon tubing. The outer braid is taken from another piece of small coax ( I
guess like RG174) and the outer of the braid is taped with Scotch 92 tape.
The core is 2.4 OD of 250 permeability ferrite. I wonder if he realizes how
complex this thing is. 73, Dan, N5AR
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com]On Behalf Of Tom Anderson
Sent: Monday, August 07, 2006 4:19 PM
To: towertalk@contesting.com
Subject: [TowerTalk] 22 ohms to 50 Ohms balun material
Fellow Tower Talk veterans:
A friend of mine in South Africa wants to buy a 2.25" ferrite core to build
a balun to match 22 ohms to 50 ohms which is described in "Building and
Using Baluns and Ununs" by Jerry Sevick. I don't have a copy of the book
and neither does he in South Africa, as he had simnply heard about the
balun. The core material is being used to replace a coax cable/balun that
KLM used on its 40m beam. Only information I have from South Africa.
Anyone who might have a copy of the book can tell me what type of ferrite
material is needed to construct thisa type of balun? I told him I'd find it
here and ship it to him in SA.
Tom, WW5L
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