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1/3/45
WAR MARKS BIG STEP FORWARD IN DEVELOPING RADIOSONDES
This country, our allies and our enemies, in order not to be at a serious disadvantage in fighting the war, check the weather in the stratosphere by means of radiosondes. For America the U. S. Army Signal Corps is, of course, charged with this responsibility, as a part of its meteorological service.
Enemy radiosondes have been captured and carefully studied and this provides interesting comparisons between our own and those of Germany and Japan. In general it may be said that German and Japanese radiosondes give fewer readings than those developed by America and therefore are less accurate. They are well built and well designed, and are smaller in size and lighter in weight than American instruments. In one notable way they are inferior to ours. Neither the German nor the Japanese instruments are designed for mase production as ours are. Their mercury thermometers and manometers are not suited for mass production since certain component parts can be made only by hand, and at least two pre calibrations are necessary.
German and Japanese radiosondes make use of techniques and measuring elements similar to those used in American instruments, but they differ in the types of such elements employed and in the method of varying the transmitted signal.
The Germans have two types of radiosondes in general use. The first type employ wet and dry bulb mercury in glass thermometers for measuring temperature and relative humidity, and a mercury fill¬ ed glass manometer for the determination of pressure. These glass tubes have metallic coils on the outside distributed through the operating length of the mercury columns within the glass tubes. Two transmitters are used, and two radio frequencies and two antennas are required. It is probable that constant tracking of the signals at the ground station is required to operate this set. The Germans also use chronoraetric radiosondes that employ bimetallic elements to measure temperature, and hair hygrometers to measure humidity. Tem¬ perature contacts are made twice a minute, humidity contacts once a minute.
The Japanese use radiosondes very similar to the German. Pressure is determined in much the same way as in the chronometric instrument of the Germans; however, there are only seven contacts.
The Jap radiosondes have the same defect as the German, that they must operate on two radio frequencies, requiring two transmitters, two antennas, and constant tracking at the ground station.
The American radiosonde operates with one transmitter. The carrier frequency is audio modulated and variation in audio modula¬ tion can be translated into meteorological data. The signal is received and graphically recorded on a chart. The number of con¬ tacts can be counted and the pressure read. Then the elevation is determined. Some American radiosondes have 80 contacts; others 95.
All three countries use a battery for their radiosonde pow¬ er supply. The foreign instruments use vibrators and transformers to obtain desired voltages and alternating currents. American instru¬ ments use batteries with the correct plate voltage and tap only cer¬ tain components of the battery for the correct filament voltages.
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