Polyester rope doesnt stretch like nylon and others. Available at Walmart
and other fine stores everywhere...made by Lehigh...polyester (not to be
confused with polypropylene) served me well for years.
----- Original Message -----
From: "Eric Scace K3NA" <eric@k3na.org>
To: <dick.green@valley.net>; "Tower (Tower)" <towertalk@contesting.com>;
"YCCC (YCCC)" <yccc@yccc.org>
Sent: Monday, October 06, 2003 6:41 AM
Subject: [YCCC] RE: [TowerTalk] follow-up on 4-square conversion
> Hi Dick --
>
> Rope: One of the problems with rope guys is that many kinds of rope
are quite stretchy. The purpose of guying is to keep the
> aluminum tubing aligned in a column; this keeps downward forces (which can
be substantial) from collapsing the column (column
> failure). To do this, any guy (rope or other material) needs to be
well-tensioned so that a sideways movement of the guy point
> doesn't merely take up the slack in the guy.
>
> The total amount of stretch in material increases as the material is
made longer; i.e., elongation under a particular load add a
> certain percent to the overall length. Long pieces of rope (e.g., the 85
feet needed to guy to the 60 ft level at a 45? angle) will
> therefore stretch more when the wind loads up the antenna (or a tree limb
falls on the guys).
>
> Consider investing in low-stretch rope for at least the longest guys,
such as those with amarid fibers. These are available at
> marine supply stores or, e.g., from New England Rope company. Low-stretch
ropes are quite strong, so you will be able to use a
> smaller diameter rope.
>
> The thinner the aluminum, the more important it is to have an adequate
number of low-stretch guys.
>
> W1KM's approach to getting enough leverage to raise the antenna is an
excellent one.
>
> 73,
> -- Eric K3NA
>
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com]On Behalf Of Dick Green
> Sent: 2003 October 6 Monday 00:08
> To: Tower (Tower); YCCC (YCCC)
> Subject: [TowerTalk] follow-up on 4-square conversion
>
>
> Thanks to all who responded to my request for info about converting my 40m
> 4-square to an 80m 4-square.
>
> I got lots of interesting ideas on extending the elements, from
ultra-simple
> (add a loading coil at the bottom) to fairly complex (anything to do with
> irrigation tubing.) I've settled on simply extending the existing elements
> with six 6-foot sections of T-6063 drawn aluminum tubing, ranging in size
> from 1.125" to .375". I'll use 4-way guying in two places (say, 35' and
60')
> with black Dacron rope. It will take nine guy anchors, five of them
shared.
> Any suggestions on the height of the guys, minimum diameter of the rope
(can
> I use 3/32"?), and how to attach the guys to the tubing would be welcome.
>
> I'm considering using rivets instead of the old cross-cut and hose clamp
> method to build the extensions. Of course, this means I'm not going to use
> the old telescoping trick I used to erect the 40m elements. Since two of
the
> existing elements have been bent from flying tree branches, and all four
of
> them have been whipping around in the wind unguyed for six years and may
be
> loaded with dirt, leaves and other debris, telescoping is either
impossible
> or inadvisable. So, my plan is to build hinges onto the mounting posts and
> raise the fully-extended elements. Some believe I can just walk them up by
> myself. The elements weigh only 20 lbs, but I'll probably ask at least one
> friend to help. W1KM had a novel method: place a 30' extension ladder
> vertically against the post, run a rope from the top of the ladder to the
> middle of the element, and tilt the ladder away from the element to the
> ground!
>
> As for the matching network, that is a more complicated question.
Quadrature
> feed is not optimal for an 1/8-wave spaced array, and it will take a
> modified Lewallan network, or something similar, to obtain a pattern with
> about 5 dB forward gain and 20+ dB F/B. There's an example of just the
> network I need in the ON4UN book. The inductors look easy to build, but
I'm
> puzzling over where I would get the caps and how much power they have to
> handle. Any help in that regard would be most appreciated.
>
> It is also possible to use a standard quadrature feed, such as the Comtek
> box. However, the pattern is not as good -- only about 4dB gain and 9-10dB
> F/B. I would imagine the bandwidth would be fairly narrow as well, but I
> only care about CW anyway. As winter is fast approaching, one option would
> be to install a Comtek box now and work on building an optimal phasing
> network over the winter. I would guess I could sell the Comtek box later
for
> a good percentage of what I pay for it. The good news is that both
matching
> methods use 1/4-wave feed lines, so I could just swap in the new network
> when it's ready.
>
> Can anyone see flaws in this plan or suggest a better one?
>
> 73, Dick WC1M
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free,
> 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> _______________________________________________
> YCCC mailing list
> YCCC@yccc.org
> http://lists.contesting.com/mailman/listinfo/yccc
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|