An Oscillation Source for Radio Receiver Investigations

A source of long-wave, sustained oscillations, for use in connection with investigations on radio receivers, and providing standard controllable signals of the same character as those due to actual radio signals, is considered. Heretofore, such sources have had the disadvantages that they necessitated the measurement of small "received currents," and also, that considerable interference was caused by stay electric and magnetic fields emanating from the elements composing the oscillation circuit. The latter makes it difficult to carry on numerous researches in the same room on the same range of wave length; while the former cannot be accomplished with present-day apparatus for the minute currents occurring in trans-oceanic reception. The source described provides an emf. of known magnitude, rather than a current, which is exactly what occurs under operating conditions. In order to devise methods of reducing the intensity of stray fields from the source, a number of preliminary experiments are made and suitable methods of shielding and construction of oscillator elements are determined. A practical source utilizing these principles is described and construction and calibration data given. Finally, the use of this type of source in connection with transmission measurements on long distance radio communication is proposed, to replace the ordinary audibility measurements.