174 BELL SYSTEM TECHNICAL JOURNAL 



the pitch of a musical tone due to the changes of overtone structure 

 are described. 



OvervoUages on Transmission Lines} C. L. Gilkeson and P. A. 

 Jeanne. Observations of Hne-to-ground voltages have been made 

 under routine operating conditions on an isolated neutral system, a 

 Petersen coil system, 3 neutral resistance grounded systems, and 2 

 directly grounded systems. Results of these observations are given 

 in this paper. Measurements were made with oscillographs supple- 

 mented, on all but 2 systems, by surge recorders. 



An Acoustic Spectrometer.^ C. N. Hickman. A series of tuned 

 reeds are mounted so that they may be electromagnetically driven. 

 Each reed carries a small concave mirror with which light from an 

 illuminated slit is brought to a focus on a screen. These slit images 

 are lined up in the order of the reed frequencies. When a current 

 having a complex wave, such as the speech current from a microphone, 

 is passed through the electromagnet, the reeds and in consequence the 

 slit images on the screen will oscillate. The driving system and the 

 reeds are so designed that the amplitude of oscillation of each image is 

 proportional to the strength of the corresponding harmonic component 

 in the driving current. Therefore, by observing or photographing the 

 slit image amplitudes, the frequencies and the relative energy content 

 of the components of a complex current may be determined. A spec- 

 trometer of this type covering a small frequency range (50 to 3109 

 cycles) was built for demonstration purposes. The range of such an 

 instrument can be extended to higher and lower frequencies. 



The Measurement of Harmonic Power Output of a Radio Transmitter r' 

 P, M. HoNNELL and E. B. Ferrell. A method of determining the 

 harmonic power output of a high-frequency radio transmitter is 

 described. It is a method for measuring the power delivered by the 

 transmitter to the antenna system, as distinguished from the more 

 common method of measuring harmonic field strengths at specified 

 locations. It is essentially a comparison method. The unknown 

 harmonic power, present with the fundamental, is compared by means 

 of a sufficiently selective receiving set with a known comparison power 

 which is supplied in the absence of the fundamental. The method in 

 practice seems to be accurate within about one decibel. It is appli- 

 cable to the measurement of power other than harmonic power. 



^ Elec. Engg., September, 1934. 



'' Jour. Acous. Soc. Am., October, 1934. 



'- Proc. /. R. E., October, 1934. 



