10 



PROPAGATION OF RADIO WAVES 



"\ATiich contour actuallj^ represents the limit of 

 detection for a given radar depends on the power 

 output of the transmitter, the minimum power 

 detectable by the receiver, the antenna gains, and 

 the radar cross section of the target. For com- 

 munication sets, the same cjuantities, except the 

 target cross section, apply. 



1* ORGANIZATION OF THIS VOLUME 



1.4.1 



Arrangement of ^Material 



This volume is composed of two classes of material. 

 One class, comprising Chapters 2, 5, and 6, is de- 

 voted primarily to the major problem of calculating 



the field strength, while the other class discusses 

 collateral problems of importance if these calcula- 

 tions are to be utilized for obtaining the most 

 effective use of radar and communication sets. 



Chapter 2 is devoted to a presentation of basic 

 relationships such as the definition of radio gain, 

 the transfer of power between doublet antennas in 

 free space, antenna gain, receiver sensiti\T.ty and 

 noise, and the definitions of radar gain and cross 

 section. 



The problem of computing the field strength or 

 radio gain at any point in the atmosphere is given at 

 length in Chapter 5, and Chapter 6 extends this 

 material to the calculation of co\'erage diagrams. 

 In Chapter 7 these calculations are related to the 



50 



Kilomelors 



Frequency 3000 Mc 

 Vertical Pdoriza-tioo 

 Antenno Height 9 meters 

 K=4/3 



Figure 11. Contours of constant radio gain factor for vertical polarization on 3000 mc over sea water. 



-lOODB 



6 3 



Kilometers 



Frequency 100 

 Horizontql Polo 

 Antenna Height 



Figure 12. Contours of constant radio gain factor for horizontal polarization on 100 mc over sea water. 



