Re: [TowerTalk] Mounting A Solenoid Balun?

[Bill Coleman <aa4lr@arrl.net>]

On Sep 29, 2004, at 10:52 PM, W7TMT wrote:

> I'm just finishing up refurbishing a 12 year old A3S and
> adding the 40 Meter kit that's been languishing in the
> basement for a long time. After researching the various
> balun options I decided to go with a solenoid style. Using
> the excellent data available on the Web by Tom, W8JI and Ed,
> WA2SRQ I'm winding 12 turns of RG-213 on a 4 1/2" PVC form.
> Unless I'm missing something that should be in the ballpark
> for 40 thru 10 meters.

I was doing something like this a few years back. I had refurbished my 
A3S and was working on a balun. I was going to use 10 turns of RG-213 
on a 4" ID PVC form. My plan was to use a U-bolt and fasten the far end 
of the PVC to the boom. In order to get to the ends of the U-bolts, one 
end of the PVC was cut at a 45 degree angle, the other cut square.

I thought about the proximity of the boom affecting the coil. A flat 
plate would act as a shorted turn and reduce the inductance. So, I cut 
about 16 inches of pipe, to position the coil a couple of diameters 
away from boom.

In the end, though, I found some #77 ferrite beads cheap that would fit 
over RG-213. I measured the impedance of one, and used 10 (about 16") 
of beads.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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