1070 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1952 



300 400 

 FREQUENCY 



600 800 1000 2000 



MEGACYCLES PER SECOND 



Fig. 1 — Median values of received signal power at suburban locations. (As- 

 sumes the same power at all frequencies radiated from a dipole and received on a 

 quarter-wave whip.) 



OVER-ALL RESULTS 



The results of many measurements of path loss between a land radio 

 transmitter and a mobile receiver establish a trend of loss increasing 

 with frequency. This is illustrated in Fig. 1 by the "crosses" which show 

 the strengths of the received signal at higher frequencies as compared 

 with those at 150 mc. The derivation of the values given by the crosses 

 will be discussed in a later section. In the other direction of transmission 

 it appears justified, based upon reciprocal relationships, to assume that 

 path losses from mobile transmitter to land receiver will follow the 

 same trend. 



However, although the received signal is seen to decrease with fre- 

 quency, the amount of received signal which is required to produce 

 satisfactory communication also changes with frequency. The median 

 level of signal required at a mobile or land receiver at various frequencies 

 to override RF noise is given in Fig. 2. The dots here represent the 

 average of many measurements. 



