[YCCC] RE: [TowerTalk] follow-up on 4-square conversion

Dick Pechie kb1h at myeastern.com
Mon Oct 6 07:55:45 EDT 2003


We have had our 80M 4-square up now for almost 5 or 6 years. Made mostly of
2" aluminum conduit except the top 16 feet (total of about 66) we have the
elements guyed four ways twice. The guying material is the rope that comes
with the military mast kits that many seem to use. The rope is almost a drab
green in color but stretching has not been a problem. I don't think we have
retensioned the guys in four years.

I hope I haven't cursed myself!

Dick- KB1H


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----- Original Message -----
From: Eric Scace K3NA <eric at k3na.org>
To: <dick.green at valley.net>; Tower (Tower) <towertalk at contesting.com>; YCCC
(YCCC) <yccc at 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 at contesting.com
> [mailto:towertalk-bounces at 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.
>
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