THE UPPPER AIR

Evening Post, Volume CX, Issue 134, 4 December 1930, Page 20

THE UPPPER AIR

A EADIO EXPLORER

Signal Corps engineers of the United States Army have devised a means by which radio can be used to determine air conditions several miles above the surface of the earth, and after more than seven years of experimentation they have perfected, at the Signal School laboratories at Fort Monmouth, New Jersey, equipment by which the direction and velocity of the winds at high altitudes may be computed with a. high degree of accuracy regardless of visibility, writes J. D. Van Brakle, in the "Scientific American." Visual observations of upper-wind conditions are impossible at night and when visibility is reduced by low-lying clouds or fog. Since many war operations are carried on behind smoke screens or after dark, it became necessary to devise a method of obtaining the desired upper-air information under .these conditions for army use. The radio method was tho answer to the problem. The radio device consists of a miniature continuous-wave transmitter which is sent aloft by means of three hydro-gen-filled balloons. Its flight is followed with a loop direction-finder, a process known as "tracking" or making a "balloon sounding." Long research was necessary before an efficient direction-finder was perfected, as it was found that the commercial instruments used in radio compass work were not sufficiently accurate for meteorological use. The loop direction-finder consists of a specially-built radio receiver of rugged construction connected to a loop antenna composed of a single tube of copper, mounted on a tripod base. To the shaft of the loop is connected a calibrated dial, graduated in degrees and fractions. This dial is used to measure the angles through which the loop turns. Except for the fact that the receiver is of the regenerative type, Signal Corps authorities refuse to divulge the details of its construction. The transmitter which goes aloft with the balloons is compact and sturdy and weighs loss than a pound. It consists of a small vacuum tube, an inductance coil of enamelled wire, a small transformer, and a small flashlight battery, the whole outfit costing about five dollars. When the battery is snapped into place at the bottom of the device, continuous-wave oscillations are started which will continue for more than two hours. This wave has been picked up from a distance of fifteen miles. The length of wire which connects the transmitter to the balloon cluster acts as an antenna. Signals arc sent at a constant frequency of 2300 kilocycles or 130.5 metres.