Chuck Etal,
The "W1JR Balun" uses a 2.4" OD ferrite core. The winding consists of 12
turns of RG141 or RG303 (the later recommended) teflon coax in a
"contra-wound" fashion. This means that half the turns are wound on and
than the coax crosses over to the input side and the rest of the turns
proceed away from the input side.
The two major advantages of this method of winding are that it lowers input
to output coupling (thus increasing higher frequency bandwidth) and
mechanically it puts the input and output ends at opposite sides thus
making it easier to connect to the antenna and feedlines.
For those who are not familiar with this winding technique (and don't have
access to the original Ham Radio September 1978 issue) it is often shown in
QST and other places, particularly where TVI is a problem. Hopefully the
above description will jog some memories of seeing it elsewhere.
Furthermore, the W1JR balun is shown in great detail in W2FMI's books on
baluns and was featured in a more recent article by W2FMI's entitled "More
on the 1:1 Balun", CQ Magazine, April 1994, Pg. 31-32
The core used is the standard 2.4" OD called the T240 by Amidon and others.
The material used is Fair-Rite type 61 (Indiana General Q-1) which has a
initial permeability of 125. If you use 12 turns, the impedance will be
greater than 500 Ohms at 80 meters and typically much greater than 1,000
Ohms from 7-30 MHz with no resonances.
I hope this helps answer your questions.
73,
Joe, 'w1JR
At 08:25 PM 7/15/2003 -0400, Chuck Counselman wrote:
>At 7:44 PM -0400 7/15/03, Joe Reisert wrote:
>>...the balun that WX0B sells I believe is a copy of the W1JR broad band
>>toroid balun design as originally described in my Ham Radio Magazine,
>>September 1978 article! Changing the core material to type 43 ferrite
>>will probably extend it down to 160 meters.
>
>
>For those of us who haven't saved our magazines from 1978, can you please
>give us the vital stat's of your broad band toroid balun design? What
>material? What size toroid(s)? How many turns of what?
>
>And do you have impedance measurements?
>
>Tnx. -Chuck, W1HIS
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