A slightly larger transmitter than most

28 Jul

An interesting (especially to an electrical engineer like myself) article from September 1960 Popular Science, about building the giant transmitter for signalling to submerged submarines. This 2,000,000 Watt VLF transmitter, costing about $100,000,000, operated at wavelengths of 6 – 20 miles (9kHz – 31kHz) and allowed communicating with submarines down to about 30 feet (10m). This small installation was later replaced with the even bigger installations working in ELF regions (3-300 Hz).

Navy build world’s most powerful transmitter

All the electricity that flows into the top hat has to get back through the ground. Dirt is a poor conductor, and Maine dirt is worse than most. “We’d copper-plate the whole peninsula if we could afford it,” remarked a Navy engineer. What they did comes pretty close. They laid 2,000 miles of No. 6 bare copper wire into a screen (every crossing individually brazed) that is buried about a foot below ground. It covers the peninsula and runs down into the ocean on all three sides – seawater is a good conductor.

The monstrous antenna system gets its broadcasting signals off coaxial cables as big as sewer pipes, laid in six-foot underground tunnels. They run to the transmitter house, a concrete pillbox midway between the two antenna arrays.

It resembles a big-city radio station – until you compare sizes. There are four final amplifiers, 500,000 watts each. The vacuum tubes are two feet high. They’re installed in duplicate, with the spares always hot and ready to operate. Coils are wound of copper pipe that a plumber could use. And the transformer … The one in your TV set fits in your hand. This one looks like a water tank for the roof of an office building.

  • Star-shaped top hat for each antenna covers area big enough for 11 Pentagons.

  • Buried copper net – electrical ground for antennas – underlies most of peninsula, trails off into sea.

  • Counterweights, riding track, keep antenna cables aloft, compensate for sway in wind.

  • Gigantic counterweight – 220 tons – is filled with special dense cement. When the antennas is up, it hangs from double sheave, the cables running to the antenna above and winch below.

  • Mad-scientist rigs in copper-lined room transfer powerful signal from transmitter (on other side of right-hand wall) to antenna lead. No one can be here when station is on air.

There’s some extra information in Wikipedia (as always) here.

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