534 BELL SYSTEM TECHNICAL JOURNAL 



which controls the dielectric and piezoelectric properties, for these lie on 

 smooth curves that do not change slope as the transition temperature is 

 approached. It is suggested that two separate and independent hydrogen 

 bond systems are involved in ADP. The transition temperature and 

 specific heat anomaly appear to be connected with hydrogen bonds between 

 the nitrogens and the oxygens of the PO4 ions, while the dielectric and 

 piezoelectric properties are controlled by the H2PO4 hydrogen bonds. 



Nonlinearity in Frequency-Modulation Radio Systems due to MuUipath 

 Propagation.'^ S. T. Meyers. A theoretical study is made to determine 

 the effects of multipath propagation on over-all transmission characteristics 

 in frequency-modulation radio circuits. The analysis covers a simplified 

 case where the transmitted carrier is frequency-modulated by a single mod- 

 ulating frequency and is propagated over two paths having relative delay and 

 amplitude differences. Equations are derived for the receiver output in terms 

 of the transmitter input for fundamental and harmonics of the modulating 

 frequency. Curves are plotted and discussed for various values of relative 

 carrier- and signal-frequency phase shift and relative amplitude difference 

 of the received waves. 



The results show that a special kind of amplitude nonlinearity is produced 

 in the input-output characteristics of an over-all frequency-modulation 

 radio system. Under certain conditions, sudden changes in output-signal 

 amplitude accompany the passage of the input-signal amplitude through cer- 

 tain critical values. Transmission irregularities of this type are proposed 

 as a possible explanation of so-called "volume bursts" sometimes encoun- 

 tered in frequency-modulation radio circuits. In general, it appears that 

 amplitude and frequency distortion are most severe where the relative delay 

 between paths is large and the amplitude difference is small. 



Propagation of 6-Millifneter W'aves.^ G. E. Mueller. One step in the 

 exploration of a new band of frequencies for communications purposes is a 

 study of the transmission properties of the medium involved. This paper 

 describes the methods and results of measurements of attenuation due to 

 rainfall and atmospheric gases at a wavelength of 0.62 centimeter. 



The one-way attenuation due to moderate rains at 0.62 centimeter is 

 roughly 0.6 decibel-per-mile per millimeter-per-hour. The gas attenuation 

 is probably less than 0.2 decibel per mile. 



Vicalloy — -I Workable Alloy for Permanent Magnets.'' E. A. Xesbitt. 

 Alloys in the region of 30 to 52 per cent iron, 36 to 62 per cent cobalt, and 4 



TProc. I. R.E., May 1946. 

 »Proc. I. R.E., April 1946. 

 9 Metals Technology, February 1946, 



