Re: AT&T microwave station, Prospect Valley, CO
- --- In email@example.com, "Albert LaFrance"
> Terry Michaels has contributed a photo of this station from a 1957
> "Lines West" magazine. This station has the unusual feature ofa "cabin in
> the sky" equipment shelter located about halfway up the tower:Thanks Terry & Albert for posting Prospect, we finally get a good look
at a 'cabin in the sky'. Another reason for short W.G. runs on early
TD2 towers was that W.G. isolators were not yet available and there was
no practical way to suppress W.G. echos. The length of waveguide
between two echo points determines the echo period which translates to
a baseband frequency when the signal is demodulated. If the W.G. is
too long the echo frequency dips into the active baseband region and
causes a form of self-interference.
I also noticed the absence of combining network cages on Prospect,
Terry's early photo of the 'site-that-must-not-be-named' in Illinois,
and the photo of Red Oak, Iowa - the 'busy Radio Relay tower...' - on
page 17 of "Communications and Defense", available on long-
lines.net/documents. This lends credence to claims that combining
networks were more difficult to design and build than Bell Labs
engineers first thought and were not immediately available when Long-
Lines mandated the Horn-Reflector in 1955 for all new TD2 route
construction. Besides, there was no need for them until TH radio was
deployed in 1961.
There were very few towers that were not ultimately equipped with
combining networks. London, Pennsylvania was one. There were a couple
Horns on the Highland, Illinois tower with only one rectangular W.G.
feeding the circular vertical run so that no combiner was needed, and
at least one horn on the Deerfield, New York Type-1 radio-relay
building was direct-fed by a single rectangular waveguide. Some of
these sites may be viewed by using the badpixels.com link listed in
John Murray's message #13379. He also has some good photos of Colorado