TOPOGRAPHY OK SITING 



117 



= 0.2'.) , 

 = 16°10'. 

 Since <i> — 6 is positive, fi is the bearing from the south. 

 The bearing is west of south since fJ is positive (p.m.). The 

 azimuth of the sun is 



180° + 16°10' = 19610'. 



A quicker solution may be obtained from a book 

 Azimuths of the Sun, H. O. 71, published by the 

 U. S. Navy, Hydrographic Office. The equation of 

 time may be obtained from a current copy of The 

 American Nautical Almanac, United States Naval 

 Observatory, Washington, D. C. 



This method will be illustrated by the data from 

 Example 1. The LAT is obtained as before. Between 

 September 23 and March 21 the sun is in south 

 declination and since the latitude in this case is 

 north, the second part of the book labeled "Declina- 

 tion Contrary Name to Latitude" is used. For 

 latitude 40° an interpolation is made between 12:40 

 and 12:50 obtaining 164°. The table is marked "the 

 angular departure of the sun west of north" for 

 readings in the afternoon, and the tabular value is 

 therefore subtracted from 360°, giving 196° as the 

 azimuth of the sun. It is usually more convenient 



to plot a curve of azimuth against time for the hours 

 during which it is expected that the observation will 

 be made. Such a curve may be used for several days 

 without much error. 



A method that is less convenient but requires no 

 calculation is the equal altitude method. This con- 

 sists in measuring the horizontal angles between the 

 sun and a mark, when the sun is at the same altitude 

 on both sides of the meridian of the observer. The 

 bisector of the horizontal angle between the two 

 equal altitude positions of the sun during the obser- 

 vations is very close to true south, and the azimuth 

 of the mark may be determined. 



A horizontal radiation pattern should be obtained 

 to determine whether the electrical and mechanical 

 axes of the antenna coincide and to discover any 

 abnormalities in the main or secondary lobes. Defec- 

 tive patterns should be corrected by appropriate 

 maintenance. 



15.3.5 



Visibility Problems 



It is frequently necessary to estimate the effect on 

 rays of intervening obstacles or the curvature of the 



Hi => 



Si 



Ul 



z 



-1 o 

 o 



+ 24 

 + 20 

 + 16 

 + 12 

 + 8 

 +4 





 -4 

 -8 

 -12 

 -16 

 -20 

 -24 



1 II 21 31 10 20..2 12 22 (II 21 I 



> y 1 i — , " » . ' ' y 



JAN FEB MAR APR MAY 



21 31 10 20 30 10 20 30 9 19 29 8 18 28 8 18 28 7 17 27, 7 17 27 



JUN 



JUL 



AUG 



SEP 



OCT 



NOV 



DEC 



SUN DATA FROM NAUTICAL ALMANAC 1945 



Figure 1. Sun data from nautical almanac, 1945. 



