128 BELL SYSTEM TECHNICAL JOURNAL 



lated waves is first reviewed in order to ascertain specifically the desired 

 performance capabilities for a commercial transmitter circuit. The factors 

 which influence or limit these performance capabilities in the two methods 

 available for the generation of frequency-modulated waves, compensated 

 phase modulation, and direct frequency modulation, are then explored. 

 It is found that each method possesses desirable fundamental characteris- 

 tics not present in the other, but with the circuits now generally em- 

 ployed with either method the modulation characteristics and carrier 

 frequency stability are interrelated so that one has a limiting effect upon the 

 other. 



A new circuit is described in which these two important characteristics 

 are independent of each other. Owing to this independence and to other 

 circuit refinements the modulation capabilities are unrestricted with low 

 distortion over an exceedingly wide range. 



A balanced electric oscillator operating at one-eighth the radiated fre- 

 quency is modulated by balanced reactance-control tubes and negative 

 feedback is used to minimize amplitude modulation and harmonic distor- 

 tion. A system of frequency division is employed together with a crystal- 

 controlled oscillator and synchronous motor in such a manner as to control 

 mechanically the mean frequency of the modulated wave with the same 

 stability as that of the crystal-controlled oscillator. The carrier, or mean, 

 frequency stability is that of a single crystal-controlled oscillator and is 

 independent of any other circuit variations. A carrier frequency stability 

 of 0.0025 per cent is possible without the use of temperature-controlled 

 crystals or apparatus. 



Neutron Studies of Order in Fe-Ni Alloys? F. C. Nix, H. G. Beyer and 

 J. R. Dunning. Neutron transmission measurements are used to study 

 order in Fe-Ni alloys. The difference in neutron transmission between 

 fully annealed and quenched alloys when plotted against the nickel content 

 displays a broad peak around NisFe and falls to vanishingly small values 

 near 35 atomic per cent Ni and pure Ni. The higher the degree of order 

 the greater the neutron transmission. The substitution of 2.3 atomic 

 per cent Mo or 4.1 atomic per cent Cr for Fe in the annealed 78 atomic 

 per cent Fe-Ni alloy caused a decrease in the neutron transmission, relative 

 to the annealed 78 atomic per cent Fe-Ni alloy, of 15.6 and 21.2 per cent, 

 respectively. The cold working of an annealed binary 75 atomic per cent 

 Ni alloy, a treatment known to produce disorder, gave rise to a decrease of 

 20.6 per cent in neutron transmission. These results demonstrate that 

 neutron techniques serve as a useful tool to study order in Fe-Ni alloys, and 

 suggest that they can be extended to study other solid state phenomena. 



"> rhys. Rev., December 15, 1940. 



