Abstracts of Technical Articles by Bell System Authors 



Experimental Determination of Helical-Wave Properties} C. C. Cutler. 

 The properties of the wave propagated along a hehx used in the traveling- 

 wave amplifier are discussed. A description is given of measurements of 

 field strength on the axis, field distribution around the helix, and the velocity 

 of propagation. It is concluded that the actual field in the helix described 

 is slightly weaker than would be predicted from the relations presented by 

 J. R. Pierce for a hypothetical helical surface. 



Results of Microwave Propagation Tests on a 40-Mile Overland Path? A. L. 

 DuRKEE. This paper gives the results of a series of microwave radio prop- 

 agation tests over an unobstructed 40-mile overland path. The purpose of 

 the tests was to investigate the transmission characteristics of such a path 

 at centimeter wavelengths over a long period of time. Statistics on the 

 transmission results at wavelengths ranging from 1.25 to 42 cm. are given. 

 The tests extended over a period of about two years. 



A Tunable Vacuum-Contained Triode Oscillator for Pulse Service? C. E. 

 Fay* and J. E. Wolfe. A tunable push-pull triode oscillator is described 

 in which the vacuum-tube components and the entire r.f. portion of the 

 oscillator circuit are contained in an evacuated metallic envelope. A 

 terminal is provided for coaxial output into a 50-ohm transmission Hne. 

 The oscillator was developed for the frequency range of 390 to 435 Mc. 

 and is tunable by mechanical means continuously through this range. Pulse 

 power of above J megawatt is obtained with pulse voltages of 15 to 17 

 kilovolts applied. 



A Proposed Loudness-Eijlciency Rating for Loudspeakers and the Deter- 

 mination of System Power Requirements for Enclosures} H. F. Hopkins and 

 N. R. Stryker. Experimental and computed data relating to the loudness 

 contribution of various ranges of the frequency spectra of speech and music 

 are correlated with the corresponding energy distribution. A relatively 

 simple measurement of sound pressure and a knowledge of certain acoustic 

 radiation phenomena are applied to this correlation to form the basis of a 



1 Proc. I. R. E., February 1948. 



2 Proc. I. R. E., February 1948. 



3 Proc. I. R. E., February 1948. 

 * Of Bell Tel. Labs. 



4 Proc. I. R.E., March 1948. 



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