The Microwave Radio and Coaxial Cable Networks of the Bell System

by moistly • 5 years ago

53 6 5 years ago

retrac2• 5 years ago

I think what amazes me most is how quickly the whole thing was built.

In 1945, there were literally a total of a few hundred phone lines fully crossing the United States. A few bundles of twisted pair running across the Colorado mountains and New Mexico desert. If you wanted to make a phone call from New York to San Francisco, you booked ahead of time and paid out the nose for a noisy line. Such services were still revolutionary -- they had only become generally available c. 1920. And there was certainly no such thing as long-distance television.

Just 15 years later, you could place a direct-dial call between almost every major city in North America, it would probably connect instantly, and cost 1/20th the rates of two decades before. The entire nation would tune in to watch simulcast television on both coasts.

They connected the majority of urban areas with broadband pipes measuring tens of MHz of bandwidth available for TV and data, and thousands of voice channels. A continent-spanning network of coaxial and microwave relay towers - multiple redundant routes with hundreds and hundreds and hundreds of those Long Line installations -- all constructed in the span of about a decade to the cost of something like $60+ billion in modern money. It's one of the greatest crash infrastructure projects any society has ever undertaken.

The system in 1960: http://www.long-lines.net/places-routes/maps/MW6003.jpg

macintux• 5 years ago

Not really all that relevant, but your comment reminded me of how quickly the Western Hemisphere was explored after Columbus. I’ve always been surprised at how accurate maps were from the 1500s; this one from 1550 just astonishes me.

https://www.maphouse.co.uk/antique-maps/the-americas/M3908-m...

Once a significant opportunity presents itself, we really can move mountains.

camkego• 5 years ago

Very interesting map. I've always thought of the TV and telephone networks as separate up until the time of the Internet. So, if the map represents Ma Bell, then of course they ran their telephone traffic over these microwave routes. But who's TV signals were being routed over the microwave routes? Was the TV portion of the microwave routes rented mostly to the public broadcast stations? (ABC/NBC/CBS/etc) ??

retrac2• 5 years ago

TV, data and telephone were often carried on the same pipe. Both the coaxial and microwave relay systems were, at their lowest level, broadband analog repeaters that just repeated whatever was sent. A repeater might take everything received between 4320 and 4340 MHz and broadcast the full 20 MHz channel on 4350 to 4370 MHz. If you sent 20 MHz of bandwidth carrying multiplexed voice channels, it would rebroadcast that to the next relay. Same with 20 MHz subchannelized to carry voice channels and two TV channels. Same with some weird digital modulation.

It was fairly agnostic to the actual contents of the channel as long as it fit within the assigned bandwidth. For example, they started using broadband digital modems to carry PCM audio by the 1970s, in parallel to the TV and FM voice. The circuit and packet-switched computer networks AT&T later provided were first carried this way too, as I understand it.

In practice, NBC/ABC/CBS were the biggest clients and used it to relay live network programming, etc. until satellites started displacing that in the 1970s. But it got used for all sorts of esoteric purposes too. Anything you needed bandwidth for, if you could afford it.

rootsudo• 5 years ago

Well, to be fair, if you compare the national highway map, proposed by Eisenhower it's almost 1:1.

Why? Federal funds, and the Government finally interconnected itself.

Amazing, not really, corporation taking advantage of a new opportunity, Yes.

8bitsrule• 5 years ago

In 1945, there were literally a total of a few hundred phone lines fully crossing the United States.

Seems amazing now, but it was only 30 years before in 1915 when Graham Bell in NYC talked to Watson in San Francisco. That was thanks to the wire finally existing and tube amplification finally showing up. (So hard to find good, close-up details on that 30 years.) 1945 when Arthur C. Clarke proposed a 3-satellite system. 1963 when Relay 1 and geosynchronous Syncom 2 showed up.

'Microwave towers' ... for those who haven't seen them, this article goes into what's left of them - with pix. [https://99percentinvisible.org/article/vintage-skynet-atts-a...]

The Microwave Radio and Coaxial Cable Networks of the Bell System

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