Abstracts of Technical Articles from Bell System Sources 



Receiver Band-Width and Background Noise} C. B. Aiken and 

 G. C. Porter. In doubling the band-width of a radio receiver, it 

 might be supposed that the apparent noise level would increase about 

 3 db since the noise energy brought in should be doubled. However, 

 the high-frequency components of noise may be very much more 

 troublesome from the standpoint of the listener than the low-frequency 

 components. An experimental study shows that this is actually the 

 case. Thus, if the noise level is low, as it should be whenever an effort 

 is made to employ high fidelity reception, the dependence of the 

 signal-to-noise ratio upon band-width is very apparent. While there 

 are many variables involved, it seems safe to conclude that in doubling 

 received band-width, the required increase in field strength may even 

 be as much as 8 to 10 db. 



Cable Sheath Corrosion — Causes and Mitigation} J. B. Blomberg 

 and NoRVEL Douglas. The causes and mitigation of telephone 

 cable sheath corrosion are dealt with in this paper, which describes 

 particularly a method of applying a counter potential to the cable 

 sheath for the mitigation of corrosion from localized currents. This 

 method, although not new, has had but limited application. It may 

 find extensive future use for controlling corrosion on intercity toll 

 cables, and in localities where street railways have been abandoned. 

 In addition to a unique application of this method, there is also de- 

 scribed the method of correcting by current drainage a particularly 

 bad case of corrosion from stray current. 



The Detection of Frequency Modulated Waves} J. G. Chaffee. 

 The comparative ease with which pure frequency modulation can 

 be produced in electron oscillators at ultra-high frequencies has led 

 to an examination of the problem of detecting a frequency modulated 

 wave. In this region of frequencies the high ratio of frequency shift 

 to modulating frequency gives rise to a very large number of side 

 bands in the spectrum representing the modulated wave. Detection 

 is usually accomplished by distorting the spectrum by means of a 



' Radio Engg., Mav, 1935. 

 2£/ec. Etigg., April, 1935. 

 ^Proc. I. R. E., May, 1935. 



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