Diversity Receiving System of R.C.A. Communications, Inc., for Radiotelegraphy

The early problems confronting the users of short wavelengths for communications are enumerated. Chief of these were fading and noise level. The phenomenon of fading is explained and the known methods of counteracting it are given. The most outstanding of these is the diversity principle. The various forms of this method are described and reasons developed for the choice of the particular form now in common use. The apparatus in general use is described in detail. In this system three spaced antennas are connected to three separate receivers. The output of each is rectified. The d-c outputs of all three receivers are combined in a common resistor, the drop in which is used to actuate means for controlling a locally generated tone which may be transferred to the receiving operator over a wire circuit. Since fading is not simultaneous in all three of the spaced antennas, a material reduction in the effects of fading is obtained. An aperiodic form of directive receiving antenna is described. Polar diagrams showing its directivity are presented. A series of measurements indicate a gain in signal-to-noise ratio of the order of 32 db for the European circuits as compared to a horizontal doublet. The effects of echo and cosmic disturbances are briefly discussed.