Moonlight from Radio Waves
February 1939 Popular Science

February 1939 Popular Science [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Popular Science, published 1872-2021. All copyrights hereby acknowledged.

This scheme from a 1939 issue of Popular Science magazine gives a whole new perspective of a "cloud warmer" radio antenna. For the most part, the portion of a transmitted radio wave that is directed within about 45-90° relative to horizon is generally considered a waste of transmitter power since the angle of incidence of ionosphere layers is too great for "skip" type broadcasts, and there are no receivers "up there" to intercept the signal. Exceeding the critical angle causes the energy to continue into space rather than to be reflected back toward the ground for long distance communications (DX). There is a sector of the amateur radio community that exploits vertically directed beams, called NVIS (Near Vertical Incidence Skywave), for local communications, but that's not the intent of the extensive array of antennas described in this "Moonlight from Radio Waves" article. Basically, it is a proposal for illuminating America's highways at night with an artificial aurora, triggered by blasting the upper atmosphere with electromagnetic energy. I've got an idea - how about installing lamps along the roadway. It would be a lot cheaper, simpler, and you'd be able to listen to your car's AM radio to boot.

Moonlight from Radio Waves

By Alden P. Armagnac

Artificial Northern Lights to Turn Night into Day

Artist's conception of a vast radio system for providing artificial moonlight over immense areas.  

Power from WLW's radio mast could create an aurora visible hundreds of miles away.

Will we light the highways of the future with artificial auroras in the night sky? Not only is the idea feasible in theory, but it could actually be tried out with apparatus now available, according to Prof. V. A. Bailey, of the University of Sydney, Australia.

His startling plan calls for hurling a vertical beam of enormously powerful radio waves to a height of fifty miles or more. Under their bombardment, the thin air of the upper atmosphere would shimmer with the bluish or greenish light of the aurora, just as radio waves make tubes of rarefied gases glow in the laboratory. A whole countryside could be flooded so brilliantly with this man-made moonlight, the Australian physicist declares, that street lighting no longer would be necessary for the safety of motorists and pedestrians.

Both station WLW, in Cincinnati, Ohio, and another high-power station in Moscow, Russia, have the 500-kilowatt capacity needed to test the scheme, Professor Bailey points out. The remaining requirement would be a special aerial system consisting of 800 individual antennas suspended horizontally at a height equal to just half of their 328-foot length, and forming a huge grid or checkerboard pattern a mile and a quarter square. With this apparatus, radio engineers could produce in the sky a synthetic "moon" or circular aurora that would be visible hundreds of miles away.

How the system works, shown by a lamp bulb held in radio-wave field to make it glow

The entire output of WLW's 500 kilowatts, strong enough for the "aurora" tests, is concentrated in this arc

Radio waves from the coil make the gas in this tube glow. The same principle forms the basis of the proposed man-made moonlight

Posted August 11, 2023