Dave -
I went through about 5 designs (failures) before we arrived at a design that
has been up here for probably 8-10 years.
I should take some pictures but anyway...
The full size 1/4 wave is made up of 2" aluminum conduit. Using couples,
bolting and lots of NoAlox, there are self standing but guyed at two points,
four times (90 degrees between anchor pins for guy ropes)
The pipe is mounted on a pressure treated 4 X 4 and that board is mounted
between two 2 X 6 planks. The beam is bolted with carriage bolts near the
top and bottom. The top is left out because when you rotate the whole
assembly up you pivot from the low point.
The bottom of the pipe is 9' off the ground with 4 raised radials each.
Measured power dump into the dummy load is usually around 5%. I guess it
could be made better but with this 2" pipe the system needs no tuning
through the whole band.
If you are a purist and not as pragmatic as I, then I am sure some
additional tuning can optimize the system more.
When I finally got these up, I began to collect Rohn 25 to replace them if
they came down. Well, 8 years later the tower sections are still being
stored. I hope I never have to use them.
BTW, the mechanical failure of earlier designs all happened at about the 33%
point up the pipes. I think if you talk to a mechanical engineer they will
tell you that is the weakest point in the structure. That is why I believe
the Hoover dam has its thickness concrete at the 1/3 point from the bottom.
What the heck, I build bridges with diodes (BSEE) not with steel girders! I
think I proved that point about 5 times!
If you want to ask more call or e-mail. Also you can visit.
I also found most of the 2" conduit in a salvage yard.
Good Luck
Dick - KB1H
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----- Original Message -----
From: "David Robbins K1TTT" <k1ttt@arrl.net>
To: "YCCC" <yccc@yccc.org>; "reflector -tower" <towertalk@contesting.com>;
"reflector cq-contest" <CQ-Contest@Contesting.COM>; <antennas@qth.net>
Sent: Saturday, December 16, 2006 10:56 AM
Subject: [YCCC] 80m 4-square materials
> I am trying to decide what to use to build 4 new 80m verticals for a
> 4-square upgrade here. My criteria are:
> 1. full size 1/4 wave verticals, no top or base loading.
> 2. must be able to standup to new England winters at 2000' with ice and
wind
> 3. must be new material, I don't want to go scrounging for used tower or
> pipe.
> 4. prefer only 1 guy level, but will do 2 if necessary.
> 5. prefer to stand up complete, but will climb to add top section(s) if
> necessary, crane or truck access will be very hard to this spot.
> 6. prefer something that can be delivered to here, truck delivery is not a
> problem, I don't want to have to haul long stuff myself.
>
> So, what might fit those criteria??
>
>
> David Robbins K1TTT
> e-mail: mailto:k1ttt@arrl.net
> web: http://www.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
>
>
>
> _______________________________________________
> YCCC Reflector mailto:yccc@yccc.org
> Yankee Clipper Contest Club http://www.yccc.org
> Reflector Info: http://lists.contesting.com/mailman/listinfo/yccc
>
>
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