There is an article titled "Broad Band 80 meter antenna" by Allan Harbach,
WA4DRU from the December 1980 issue of QST that can be found in the ARRL
members area. I think this is the article duplicated in one of the ARRL
Antenna Compendium volumes or maybe Wire Antenna Classics. Allan used
4-foot spreaders and achieved a 2.18:1 at 3500 and 2:1 at 4000 kHz. Pretty
impressive for a four-wire cage.
I think any cage will improve your bandwidth, but a larger diameter should
provide more bandwidth. To get full coverage of 80 to 75 with 2:1 SWR
bandwidth might require a really, really fat cage. But most of my 75 meter
operation isn't above 3900, which helps some.
Seeing the really cool looking cage dipole at W1AW was what got me thinking
about this sort of antenna for my "next station".
http://www2.arrl.org/news/stories/2001/05/03/2/
Since then I've acquired a Johnson KW Matchbox, so I may end up with
something else entirely. Probably something I'll have to tune every 40 kHz!
I googled for Cage Dipole and found a reference in this article to a
modeling aid and some discussion of the diameters involved.
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/IVee8
0.htm
Dick, K6KR
From: W5CPT [mailto:w5cpt@bellsouth.net]
Sent: Sunday, December 07, 2008 2:59 PM
To: Dick Dievendorff
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] Cage Vertical ideas wanted.
Dick,
Thanks for the "heads-up". I never have figured out how to model an
antenna. I really didn't think I could cover both the 75 & 80M bands. I
had hoped to broaden the bandwidth enough that I didn't have to re-tune
every 40 KHz. I guess I could use the tie-wrap idea on a larger circle but
don't have a clue what I could use to make a 24" diameter spreader, though
it is intriguing.
Clint - W5CPT
----- Original Message -----
From: Dick Dievendorff <mailto:dieven@comcast.net>
To: 'W5CPT' <mailto:w5cpt@bellsouth.net>
Sent: Sunday, December 07, 2008 4:35 PM
Subject: RE: [TowerTalk] Cage Vertical ideas wanted.
Is a 6" cage going to give you enough bandwidth? I have a bunch of circular
plastic spreaders for 4" in diameter, and after a little modeling I decided
that they weren't going to be much help for a 75/80 meter dipole. I think I
need spreaders that are on the order of 2 feet long for a four-wire cage
that went from 3.5 to 4.0.
73 de Dick, K6KR
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of W5CPT
Sent: Sunday, December 07, 2008 2:30 PM
To: Jim Hargrave; Tower
Subject: Re: [TowerTalk] Cage Vertical ideas wanted.
Thanks Jim,
That is exactly the kind of solution for which I was looking!
Clint - W5CPT
----- Original Message -----
From: Jim Hargrave
To: Tower
Sent: Sunday, December 07, 2008 3:51 PM
Subject: Re: [TowerTalk] Cage Vertical ideas wanted.
Clint,
You can use the thin drain pipe and drill the attaching holes through the
side of each ring. Then you can attach the antenna wires to the ring by
using small nylon cable ties. Pass them thru the hole and out one end
clamping each wire in the same manner. This will keep the spacing
consistent. if you drill the holes near one end of the ring, the ties will
be short and hold the wire tight enough to keep the ring from sliding down
the antenna. You can even wrap the cable around the ties before closing it
to provide a little more friction to better hold it in place.
* 73's Jim W5IFP *
>-----Original Message-----
>From: towertalk-bounces@contesting.com
>[mailto:towertalk-bounces@contesting.com]On Behalf Of W5CPT
>Sent: Sunday, December 07, 2008 7:14 PM
>To: towertalk@contesting.com
>Subject: [TowerTalk] Cage Vertical ideas wanted.
>
>
>I have decided to build a Cage Vertical. I can get about 80 to
>100 feet straight up by suspending it from a catenary strung
>between two of my taller trees.
>
>
>
>Two points:
>
>
>
>1 The wire I intend to use is Fishing Line. I tried to post the
>link but it ends up being 3 lines long, so go to cabelas.com
>and search for item number wt-12-1511. I built a dipole out
>of this stuff and it solders and crimps well and appears to
>last for a long time.
>
>
>
>2. I need ideas on what to use for spreaders. The 45 lb. test
>line is .037" which is too big to use a thin slice of 6" PVC
>drain pipe as I cannot drill holes edgewise into the pieces
>large enough to accept the wire and small enough to not
>compromise the strength of the slice of PVC. I am considering
>5 or 6 wires in a 5 to 6" diameter and need some suggestions on
>what to use.
>
>
>
>Suggestions about the spreaders and other comments are always welcome.
>
>
>
>Clint - W5CPT
>
>
>_______________________________________________
>
>
>
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>
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