Date: Fri, 13 Apr 2012 17:06:11 +0100
From: Steve Hunt <steve@karinya.net>
Subject: Re: [TowerTalk] Balun Recommendation
Some designs here:
http://www.karinya.net/g3txq/chokes/
8 turns on a FT240-31 core is good for 20m thru 10m - it gives >2k Ohm
choking impedance across the range and is predominantly resistive.
Steve G3TXQ
On 12/04/2012 17:10, Tom Harke wrote:
> I am in the process of building a number of OWA's for 10,15 and 20 meters.
> I am looking for a recommendation for a good current balun.
>
> Thanks
## Steve, does this mean 8 turns of RG- 58 on a single core. Will a single
core even handle
1.5 kw CCS CXR + SWR. RG-58 is junk, so it would have to be wound with
RG-303 teflon coax
or similar.
## what about using .25 or .75 or 1.25 wavelength of coax, with the shield
bonded to the top of the tower.
I mean a physical .25 or .75 or 1.25 wavelength... minus 2%. The Z at the
feed point would be sky high.
Then no requirement for a conventional balun at all.
## His OWA yagis are all monobanders, so cutting a .25-.75-1.25 wave length
of coax for each band
is no big deal. It just has to reach from the feed point to the top of the
tower. That will depend on
how long the booms are. Use a good bulk head type connector at the top of the
tower, and the bulk head
connector can then also be used to interface to the heliax or what ever cable
he uses to run down the
side of the tower.
## 4 turns of RG-393 or RG-213 on 4 stacked FT-240-31 cores will also work,
provide they are well
away from the boom. If they are mounted dead center in a nema box, then no
stray C to boom.
## 22 x type 43 beads, of the 1.125 inch long x 1 inch diam x .515 inch ID
variety, slid over RG-213
or RG-393 coax will also work. Slid over RG-393, and you will never overheat
them.., not even with 10 kw.
Jim VE7RF
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