Waveguide (was "size a major consideration...") [Telecom]

Temporary moderator wrote:

I'm surprised at the difference in loss of waveguide vs. coax:
all the cell sites I've ever seen appear to use coax, so either
they're using the flexible type [of waveguide] or the cellular
engineers are employing the coax loss to contribute a large part
of their loss budget for the antenna arrays being used.

I think what you're seeing on cell towers is flexible waveguide
("Heliax"): http://tinyurl.com/cudezg

Back in the good ol' days (before this fiber optic stuff came along), many of us older cable guys used flexible waveguide for 12- and 18-GHz microwave transmission systems. We could transmit the entire CATV spectrum over a distance of about 25 miles. Back then, of course, the "entire CATV spectrum" only extended up to about 400 MHz, or channel 53.

These systems could be used to distribute signals throughout a city, or to distribute signals to distant communities in rural areas. In the 1970s and early 80s, hundreds of these systems were in use.

These systems used the same off-the-shelf RF transmission components -- antennas, radomes, waveguide, connectors -- that manufacturers were making for other industries. At the time, Andrew was the biggest manufacturer in the business. You could see those big Andrew microwave antennas (easily identified by the red "lightning flash" logo on the radome) hanging on water towers in small towns all across America.

Most of the radio equipment was manufactured by Hughes Aircraft Company. When I first got into the cable business, I was surprised to learn that a big defense contractor like Hughes was making stuff for the cable industry. But in retrospect, it makes sense: the stuff Hughes was building for the cable industry wasn't much different from the stuff they were building for other purposes. The basic components were essentially the same.

Of course, once fiber came along, all this microwave stuff suddenly became obsolete. Most of the old microwave systems have been replaced with fiber, and the equipment has been removed. Some of it has been sold to cable companies in South America, but most of it has been recycled or junked.

Neal McLain
Retired Cable Guy



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Relevant Pages

  • Waveguide (was "size a major consideration...") [Telecom]
    ... > I'm surprised at the difference in loss of waveguide vs. coax: ... > all the cell sites I've ever seen appear to use coax, ... > engineers are employing the coax loss to contribute a large part ... Back in the good ol' days, many of us older cable guys used flexible waveguide for 12- and 18-GHz microwave transmission systems. ...
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