[TowerTalk] Safety of unguyed tower

[David Jordan]

I can see why Doug likes this old antenna... QRZ says he was born in 1908... 
he probably knew the Collins brothers ;-)

Quit an undertaking for a guy 104 yrs old.

73,
Dave
wa3gin
----- Original Message ----- 
From: "Steven H Sawyers (na0ia)" <steve at sawyers.org>
To: <TowerTalk at contesting.com>
Sent: Tuesday, January 17, 2012 11:46 PM
Subject: Re: [TowerTalk] Safety of unguyed tower


> From the verbal description, I think these are like antennas that
> Collins Radio had at their Comm Central Operation in Cedar Rapids
> Iowa. Twin towers with the rotor at the bottom between the towers on
> a trunion and an 8 -10 inch mast going up to a log periodic antenna.
>
> I think this type of tower was originally designed in the 1950s. The
> tower/antenna was designed to be erected by being assembled
> horizontally The towers would be hinged to the foundation.They would
> be pulled up to vertical using a winch truck pulling horizontally,
> over an A frame to start the lift. The truck was placed about two
> tower heights from the tower base away from the tower to keep the
> pull as horizontal as possible. Lift off was the tricky part.
>
> Once the towers were in place and guyed, the log periodic antenna was
> assembled up side down with the mast on top and the rotor sitting in
> the trunions. The winch line was run from the truck over the top of
> the tower and down to the  top of the horizontal mast. As the mast
> was pulled up, the antenna would pivot. First dropping to vertical as
> the top of the mast rose. When the mast reached vertical, the top of
> the mast was restrained in a bushing or bearing of some kind between
> the two towers. The log periodic antenna continued to pivot around
> the top of the mast to get to it's final horizontal orientation.
>
> One of the  interesting features of the assembled antenna was the
> fact that the rigid 50 ohm feed line ran up the center of the mast
> and had a rotary slip joint on the bottom below the rotor that
> permitted continuous rotation.
>
> Steve
>
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