The lengths of the radio waves used in ordinary U. S. broadcasting range between 200 and 547 metres. Short-wave broadcasting uses waves around 50 metres in length. Last week "micro" rays only 18 centimetres (7.09 in.) long carried two-way conversations across the English Channel. International Telephone & Telegraph Laboratories and Le Matériel Télephonique of France made the test. Simple equipment did the work. Sending and receiving devices were practically the same. Each device consisted of a vacuum tube which transformed telephone frequency into the high micro-ray frequency of 1,600,000,000 oscillations a second. Wires carried the oscillations to an antenna two centimetres (less than one inch) long. The antenna was fixed at the focal points of two curved reflectors which faced each other. One, facing in the direction messages were to be sent, was ten feet in diameter. The other suggested a motorcar headlight. The two reflectors concentrated the waves which the antenna emitted into a sharply defined beam. Two of these devices were set up, about 100 yd. apart, on each side of the Channel. The large reflector of the one functioning as a transmitter on one shore pointed at the large reflector of the receiver on the opposite shore.
The receiver caught the radio beam and focused it on the receiver antenna, whence it was carried and transformed into audible waves.
Power required was one-half watt, which is just enough to light a flashlight. I. T. & T. reported that the micro waves do not fade, and are not affected by fog, rain or other climatic conditions. The company claims that the wavelengths can be controlled so precisely that 250,000 transmitters could broadcast simultaneously. Thus television, which needs many wavelengths, finds a new tool. I. T. & T. intends to commercialize the apparatus at oncefor use on ships, lighthouses, airplanes.