Abstracts of Technical Articles from Bell System Sources 



Shared Channel Broadcasting} C. B. Aiken. This paper deals 

 with the experimental studies made on the character and causes of 

 interference noticeable in shared channel broadcasting, such as hetero- 

 dyning, flutter, sideband interference and wobbling. Valuable data are 

 included on the characteristics of square-law and linear detectors anent 

 to interference. 



The Determination of Dielectric Properties at Very High Frequencies.^ 

 J. G. Chaffee. A simple method of determining the dielectric con- 

 stant and power factor of solid dielectrics at frequencies as high as 20 

 megacycles, with an accuracy which is sufficient for most purposes, 

 is described. The major sources of error are discussed in detail, and 

 several precautions which should be observed are pointed out. 



Measurements of the dielectric properties at 18 megacycles of a 

 number of commonly used materials have shown that in general the 

 power factor and dielectric constant are not widely different from those 

 which obtain at frequencies of the order of one megacycle. 



In addition, the results of an investigation of the input impedance of 

 vacuum tube voltmeters at high frequencies are described as an illus- 

 tration of the further application of this method of measurement. 



Optical Factors in Caesium- Silver-Oxide Photoelectric Cells.^ H. E. 

 Ives and A. R. Olpin. This paper describes an investigation of the 

 part played by the angle of incidence and state of polarization of the 

 exciting light in producing the enhanced or selective emission of photo- 

 electrons in the red region of the spectrum which is characteristic of 

 photoelectric cells made by treating a silver surface with oxygen and 

 caesium vapor (Fig. 1). This question is one which has been raised in 

 connection with all types of photoelectric cells having composite sur- 

 faces and which exhibit spectrally selective emission. It has thus been 

 an open question whether the selective peaks in the spectral response 

 curves exhibited by the alkali hydride cells are to be ascribed to an 

 enhanced effect of the perpendicular vector of obliquely incident 



^ Radio Engineering, June, 1934. 



2 Proc. I. R. E., August, 1934. 



* Jour. Op. Soc. Am., August, 1934. 



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