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Re: [TowerTalk] Folded dipole

To: Tower Talk List <towertalk@contesting.com>
Subject: Re: [TowerTalk] Folded dipole
From: Steve Hunt <steve@karinya.net>
Date: Wed, 26 Aug 2009 20:14:38 +0100
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Jim,

Quite so! In the measurements and modelling I've done on folded dipoles, 
nearly all the VSWR bandwidth enhancement (around 97% of it) can be 
attributed to the "fatter" conductor; the contribution caused by the 
changing parallel impedance of the "inherent" series-connected, 
quarter-wave stubs was minimal (3%).

73,
Steve G3TXQ

Jim Brown wrote:
> If I wanted the SWR bandwidth improvement of a folded dipole (nice 
> for 80/75M and 10M), I would simply build an ordinary dipole, but 
> making the conductors fatter by building a 2-wire or 3-wire dipole 
> with spacers. That would allow me to feed it with coax, which in 
> turn allows me to put a good coaxial ferrite choke up at the 
> feedpoint to kill noise pickup on the line. If it was a low dipole 
> for NVIS, I would use 50 ohm coax. If it was a high dipole, I would 
> use 75 ohm coax.
>
> There are lots of easy ways to build spreaders. I buy 1/2-inch UV-
> resistant PVC conduit, cut it into suitable lengths, and drill holes 
> through the pieces for the wires to pass through. Some folks use 
> wood dowels that they seal against moisture. 
>
> 73,
>
> Jim K9YC
>
>
>
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