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Re: [TowerTalk] Custom antenna design

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Custom antenna design
From: Michael Tope <W4EF@dellroy.com>
Date: Fri, 20 Sep 2013 13:06:49 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Matt,

Contrary to the caption which says "Monster on a 500 inch turning radius", it looks like the design you linked to uses an actual turning radius of 250" (20.8ft). This makes sense as fundamentally there is no reason why the linear dimension of this sort of antenna shouldn't scale with frequency (actually wavelength, they inverse scale with frequency) to first order. IMO, it wouldn't take much fixed loading or tip folding to tighten up the turning radius to 18ft. On the other hand, 4S7AB model predictions aren't terribly impressive. It doesn't look like it models out much better than a rotary dipole. Perhaps it is very frequency sensitive and works much better above or below that particular frequency.

73, Mike W4EF........

On 9/18/2013 9:38 AM, KM5VI wrote:
Extrapolation of scaled dimensions is not a good assumption in this case...
see link (and others)....  or model one.

http://www.qsl.net/4s7ab/broadbandhexbeam40m4s7ab.htm

KM5VI


-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
Michael Tope
Sent: Wednesday, September 18, 2013 9:37 AM
To: Charlie Gallo
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] Custom antenna design

Charlie,

I think the columns are shifted to the left by one because the 40 meter
version is speculative (i.e. there is no actual model number assigned).
Just by rough scaling, it wouldn't make sense for the 40 meter version to
have a 40ft turning radius. A 40 meter version with a 19ft turning radius
and weight of 40 lbs is a much more sensible extrapolation when you look at
the 30 meter and 20 meter specs.

73, Mike W4EF..................

On 9/18/2013 5:29 AM, Charlie Gallo wrote:
On 9/18/2013 Michael Tope wrote:

I think the 20 meter "Hex-Beam" has a 9.4 ft turning radius, so it
stands to reason that a 40 meter version could (with a little
tweaking) be made to fit inside an 18ft circle. In fact if you go to
the "Traffie Technology" specs page you see what looks to be an
incomplete entry for a 40 meter monoband version presumably with a
19ft turning radius and weighing 40 lbs:
ttp://www.hexbeam.com/specs.shtml
73 Mike W4EF.................
Except they list the 40m as having a 40 ft turning radius...





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