Hello to All,
The question of a full size 1/4 wave vertical element has been bouncing
around for some time now. Many years ago I recall seeing at a Radio Contest
Club Meeting photos of a Four Square made with full size free standing
aluminum 1/4 wave elements for 75 meters. I have never been able to get the
construction details. One would think with all the Professional Engineers
that hold Amateur Radio Licenses a design would have been made available to
one of the reflectors by now. We will just have to keep hoping I guess.
To put a 70 foot free standing element up and expect it to be there the next
day needs a little engineering thought to say the least. Even to design an
element to be guyed has to be strong enough to be moved from the horizontal
to vertical position without bending on itself.
Using the information given in the ARRL Antenna Handbook on 6061-T6 Aluminum
Tubing. I came up with my own design idea for a free standing 71 foot
element. Starting with a 4 inch Aluminum pipe 6 foot section tapering to a
1/4 inch pipe 11 foot section with a 1 foot overlap a 71 foot element could
be achieved. Not being a Professional Engineer I have no way to know if my
design idea would work. I have included a detailed list of pipe sections. I
am hoping someone would be willing to do the calculations and share the
results.
Material : 6061-T6
Section overlap : 1 foot
Base supported at bottom and 5 foot point.
Cement/rebar cage footing : 3x3x6 foot
Soil : wet beach sand
O.D. inch I.D. inch Wall inch Length in feet
4 3.5 .25 6
extruded
3.5 3 .25 6
extruded
3 2.5 .25 6
extruded
2.5 2 .25 6
extruded
2 1.5 .25 6
extruded
1.5 1 .25 6
extruded
1 .884 .058 6
drawn
.875 .759 .058 6
drawn
.750 .634 .058 6
drawn
.625 .509 .058 6
drawn
.5 .384 .058 6
drawn
.375 .259 .058 6
drawn
.25 .134 .058 12
drawn
----- Original Message -----
From: "Jim Hill" <w6ivw@cox.net>
To: <towertalk@contesting.com>
Cc: "Kelly Taylor" <ve4xt@mb.sympatico.ca>
Sent: Saturday, March 22, 2003 7:47 AM
Subject: Re: [TowerTalk] mechanical construction of 80m vertical
> Could be, but N6RK, what is the wall thickness of the tubing you
> used? Next time I'm in that area, I'll stop by, talk to them again and
get
> more info.
> 73's Jim
>
>
> At 08:03 PM 3/21/2003 -0600, you wrote:
> >Hmmm,
> >The stuff I saw on the rainforrent Web site seems entirely unsuited to
large
> >vertical antennas. They call it lightweight aluminum, which would suggest
> >its designed to cross horizontal spans and be supported at regular
> >intervals.
> >
> >Seems to me the cheapest solution is to simply build a non-conductively
> >guyed tower using used bits. I think 40 or even 50 feet of guyed GN or
> >whatever is available, topped with an appropriately sized stinger (or
> >top-loading of some description) would not be that difficult or costly,
> >compared with trying to engineer complicated plastic towers or risking
> >mechanical failure by failing to get proper materials. It's probably even
> >easier when you consider the nightmare that trying to get flimsy tubing
> >vertical would be. It would be like pushing on a string. Shouldn't be too
> >hard to either insulate from base or feed with a gamma.
> >
> >You can often get GN for free just by taking it down for someone who no
> >longer uses it. Properly inspected, there's no reason it couldn't
continue
> >to provide years of service. Even if you had to order it from RS, I think
> >the sections are still cheaper than Chris's estimated shipping costs plus
> >material. Looking at the TT web page, even if he started with 2.125 OD
drawn
> >tubing, that's $3.50 US per foot, or almost $150 Cdn (assuming a 20-foot
> >first section and including shipping). Heck, 2 sections of GN new won't
cost
> >that and the tubing vertical would still need to be guyed.
> >
> >I would worry that trying to be frugal on this project will end up being
> >more expensive, particularly if it results in personal liability claims.
> >Probably best to do it right or not at all.
> >
> >73, kelly
> >ve4xt
> >
> >
> >
> >----- Original Message -----
> >From: "Jim Hill" <w6ivw@cox.net>
> >To: <towertalk@contesting.com>
> >Sent: Friday, March 21, 2003 4:45 PM
> >Subject: RE: [TowerTalk] mechanical construction of 80m vertical
> >
> >
> > > Finding tubing isn't easy. I've stopped at a number of businesses in
> > > farming areas with little luck. plastic tubing seems to be currently
used.
> > > However, the following store in Bakersfield CA is a good choice:
> > >
> > > The Irrigation Store, 4001 State Road, Bakersfield, CA 93303 661-4421
or
> > > 800-742-7246. Their web site is: http://www.rainforrent.com/ Their
web
> > > site shows tubing with end connections, but I thought I saw just plain
> >pipe
> > > when I visited them. The web site also shows stores at other
locations.
> > >
> > > 73's Jim
> > >
> > > _______________________________________________
> > >
> > > 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
> >
> >_______________________________________________
> >
> >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
>
> _______________________________________________
>
> 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
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