No Static on Micro-Waves (Jan, 1932)

No Static on Micro-Waves

LIVELY interest has been aroused, among television and short-wave enthusiasts, in New York City, by the present activities of the National Broadcasting Company, in regard to experiments on ultra-short waves. Apparatus is being set up in the tower of the lofty Empire State Building, and short antennas erected about its mooring mast. While official information has not been forthcoming as to wavelengths and schedules, it is evident from the dimensions of the antenna that the work is on ultrashort waves, such as are now being similarly tested in Holland and Germany.

The ultra-short wave is readily reflected, so that it does not pass beyond the horizon of the antenna; and obstacles such as hills cast shadows in its path. It is therefore adapted only to local broadcasts of this nature, so far as present knowledge goes.

The “micro-wave,” however, is in still another order of wavelength—less than a meter (39.37 inches). It is even more markedly “quasi-optical”—that is, subject to the laws governing the transmission of light; but with extremely low power it is capable of transmitting distinct signals between any two points between which there is a clear space. Recent experiments were very successful across the English Channel.

The Marquis Marconi, who has always taken especial interest in short-wave work, states in a recent interview that he is now working on 10- to 20-inch waves (25 to 50 centimeters) on distances between ten and twenty miles, with perfect speech transmission. These waves penetrate brick and wooden walls readily, though steel-frame buildings reflect them. Since their frequency is above that of interference from “static” and electrical appliances, reception is unmarred by noise.

The particular value of the micro-waves for television is shown by the fact that they may be modulated with wavebands a hundred times wider than those used for ordinary broadcasting; and therefore they are adapted to the transmission of the most detailed images; while, for local programs, perfect reception, free from “atmospherics” and “man-made static,” may be relied upon. At the present time, the entire spectrum of micro-waves, with its numerous channels, is open for experiment by all licensed stations. Developments in the next year will be rapid.

“The great advantage in the use of ultra-short waves which has been yet discovered is that there is a complete absence of the static and fading, so troublesome on somewhat longer waves. Operation, also, is extremely economical.”

—Marconi

3 comments
  1. Stephen says: November 29, 20116:36 am

    The other great advantage of “micro-waves” is of course that they are reflected off large objects and come back to the transmitter with a time delay proportional to the distance covered. Put your microwave transmitter on a rotating turntable, add a display which shows up where reflections appear, and you can detect aircraft from miles away. In 1932, though, this was still in the future. The cavity magnetron, the first efficient device for making microwaves, didn’t appear until 1937.

  2. hwertz says: November 30, 20115:21 pm

    How did they make microwaves before the magnetron?

  3. Jari says: December 1, 201111:53 am

    hwertz: Two-pole magnetron was actually invented in 1920. In 1924 it was discovered, that it could generate waves at 100Mhz-1Ghz. Before 1920, who knows?

Submit comment

You must be logged in to post a comment.