Post by Matt Blaze

For much of the 20th century, the backbone of the AT&T "Long Lines" long distance telephone network consisted primarily of terrestrial microwave links (rather than copper or fiber cables). Towers with distinctive KS-15676 "horn" antennas could be seen on hilltops and atop switching center buildings across the US; they were simply part of the American landscape.

Most of the relay towers were simple steel structures. This brutalist concrete platform in San Jose was, I believe, of a unique design.

The San Jose Oak Hill Tower is unique in a number of ways. This particular concrete brutalist design appears not to have been exactly replicated elsewhere; it was site-specific. It sits atop an underground switching center (that was partly used for a military contract), which explains the relatively hardened design.

Today the underground switch is still there, owned by AT&T, but the tower space is leased to land mobile and cellular providers. The old horn antennas at top are disconnected.

With a few exceptions (mostly towers atop downtown switching offices in populated areas), no one was trying to make any of this utilitarian communications infrastructure beautiful. It was form strictly following function, built to be reliable and rugged.

But there was, I think, quite a bit of beauty to find in it. Perhaps we'll look at our current neighborhood cellular towers, now often regarded as visual blight, the same way decades after they're (inevitably) gone.

Infrastructure is heroic.

@mattblaze An increrdible construction, especially for a network engineer. It's size feels difficult the judge correctly, even if a few hints could give it away, but the adjustment of perspective doesn't help. Great shot !

@PorCus The horn antennas are 11 feet across and 20 feet tall!

@mattblaze
A friend of a friend bought one of those sites, primarily to get the diesel generators that made the mechanical UPS power supply. A motor spun a heavy flywheel as long as there was utility power. If the power failed, an electromagnetic clutch dropped out, the motor turned into a generator and the flywheel spun up a diesel motor to power to the electronics at the site. There were two such generators on the site. They had to be serviced on a regular basis but we're in fine shape. One such motor/generator was a heavy load for my utility trailer.

@Dougfir I've seen those in operation. Very impressive.

Understanding flywheels as kinetic capacitors is instructive.