Sri: I was relying on my memory rather than the instructions. 5 turns on a
6 inch diameter at the connection of the feedpoint to the driven element is
what's listed on page 7 of the Classic 33 WARC manual. When you use the 40
meter kit they recommend a couple more turns on 8 inch inside diameter.
Pardon the error.
Mosley also recommends if you have any questions give their tech line a
call. The number listed in the instruction manual is no longer valid, but
its on their website.
Tom, WW5L
----- Original Message -----
From: "Bill Coleman" <aa4lr@arrl.net>
To: <ww5l@gte.net>; <w7why@harborside.com>
Cc: "TowerTalk" <towertalk@contesting.com>
Sent: Friday, November 16, 2001 8:40 AM
Subject: Re: [TowerTalk] How to mount choke balun?
> On 11/15/01 11:07 PM, Tom Anderson at ww5l@gte.net wrote:
>
> >I've got a Mosley Classic 33 WARC and they recommend an 8 inch diameter
> >coil of RG8 for that antenna, 10 inch if you use the 40m kit on the ends
> >of the driven element.
>
> How many turns?
>
> One problem with a coaxial balun is you don't want too many turns. You
> have to have enough turns to give sufficient inductive reactance at the
> lowest frequency, but too many turns actually makes the balun ineffective
> at higher frequencies.
>
> Back in 1995, Ed Gilbert posted a great message about actual measurements
> of air-core coaxial baluns, which is referenced here:
> <http://www.k1ttt.net/technote/airbalun.html>
>
> One of Ed's conclusions:
>
> - Don't use too many turns. For example, the HyGain manuals for my 10
> and 15 meter yagis both recommend 12 turns 6 inches in diameter. At
> the very least this is about 3 times as much coax as is needed, and
> these dimensions actually give less than the desired choking impedance
> on 10 and 15 meters.
>
> --
>
> 6-7 turns on a 4-inch PVC makes a great balun for 20-10m, and 12 turns on
> a 4-inch PVC works from 40-10m, assuming a 50ohm feedpoint.
>
>
> Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>
>
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 100 feet for under $1500!! http://www.anwireless.com
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|