At 03:43 AM 9/10/2006, Tom Rauch wrote:
> > Using three separate insulators, one in each leg of a
> > guyed tower, is about the WORST possible approach.
...
> It's far better on guyed towers to bring all three legs to a
>single point or a very stiff flat plate and have the tower
>sit on a single pin on top of or below an insulator.
TopBanders,
I offer as an example some photos of the 1200 foot tower (now gone) at NSS
Annapolis Naval Communications Station.
The website with a number of pictures:
http://hawkins.pair.com/nss.shtml
A shot of the base of the tower. Note that the lower anti-corona ring is
roughly SHOULDER high, and each of the six main load bearing insulators is
the size of a large trash can.
http://hawkins.pair.com/nss/nss05e.jpg
Somewhere in that assembly is a hemispherical bearing that allows for
slight tilting motion it all directions. The antenna, a mile long in
total, operated at roughly 800,000 watts at 20.4 Kilocycles.
This picture shows the lighting isolation transformer at the central
tower. The people give scale to the insulators used. The upper corona
ring is roughly 10 feet in diameter This assembly does not carry any
weight, but just provides RF-isolated lighting power for tower lights.
http://hawkins.pair.com/nss/nss06a.jpg
A further note: information at the bottom of the page about white noise
being transmitted does not apply to this transmitter. It sent narrow band
frequency shift keyed teletype signals. The Mark and Space frequencies,
even though separated by a very small degree, fell down the slope on each
side of the antenna response curve. A common Tektronix oscilloscope
monitored antenna current and allowed the operator to tune the antenna for
equal currents for mark and Space. The information was encrypted, likely
at Norfolk, and sent to the transmitter site in Maryland via land lines (at
least). The operators said they never knew what was being transmitted.
Roy
- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing
13033 Downey Mill Road, Lovettsville, VA 20180
Phone 540-822-5911 Cell 301-928-7794
Work: Voice: 301-975-3254, Fax: 301-975-6097
roy.morgan@nist.gov --
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