478 THE BELL SYSTEM TECHNICAL JOURNAL, APRIL 1951 



Test of 450-Megacycle Urban Area Transmission to a Mobile Receiver* 

 A. J. AiKENS^ and L. Y. Lacy.i I.R.E., Proc, v. 38, pp. 1317-1319, Nov., 

 1950. 



Abstract — Measurements were made of mobile radio- telephone trans- 

 mission at 450 Mc in New York City using frequency modulation. Compari- 

 son was made with transmission at 150 Mc using identical speech modula- 

 tion. Effective radiated powers were about equal. Direct comparison tests 

 were made with the receivers installed in a moving automobile. The trans- 

 mitter and the receiver used at 450 Mc were developed especially for the 

 job. The receivers used at the two frequencies had substantially the same 

 noise figures. The tests permitted estimates of the relative magnitudes of the 

 shadow losses at the two frequencies and included measurements of r^ noise. 

 Subjective tests of circuit merit comparing the two frequencies were made 

 by a number of observers. 



Pressure Broadening of the Ammonia Inversion Line by Foreign Gases: 

 Quadrupole-Induced Dipole Interactions* P. W. Anderson.^ Phys. Rev., 

 V. 80, pp. 511-513, Nov. 15, 1950. 



Abstract — ^The broadening of the 3,3 line of the inversion spectrum of 

 ammonia by foreign gases which are not expected to have dipole or quadru- 

 pole moments has been measured accurately by Smith and Howard. This 

 broadening is greater than that previously computed by the author using 

 the interaction of the molecule's dipole moment with the induced dipole 

 on the foreign gas atom. In this paper the broadening is explained quanti- 

 tatively using the interaction of the induced dipole on the foreign gas atom 

 with the quadrupole moment of ammonia. It is concluded that a model of 

 the ammonia molecule using bond dipoles of the appropriate size to give 

 the known dipole moment, or a model with point charges at the atoms, 

 again adjusted to give the correct dipole moment, both give quadrupole 

 moments which explain the broadening cross sections with good accuracy. 



Antenna Systems for Multichannel Mobile Telephony* W. C. Babcock^ 

 and H. W. Nylund.^ LR.E., Proc, v. 38, pp. 1324-1329,. Nov., 1950. 



Abstract — This paper describes an arrangement whereby several antennas 

 may be mounted on a single mast at the transmitting site of a multichannel 

 system operating in the 152- 162-megacycle band. The antennas are so dis- 

 posed as to minimize shadowing effect of the mounting structure, while 

 keeping intertransmitter coupling to a tolerable minimum. Measurements 

 of the electrical characteristics are presented for arrangements of 6 antennas 

 mounted on a 62-foot steel mast. These measurements on a full-scale struc- 



* A reprint of this article may be obtained on request to the editor of the B. S. T. J. 



