198 



GLOSSARY 



r. 1) Distance from center of antenna to a point in 



space (usually replaced by d in applications) 



2) Height wavelength factor 



3) Pattern or chart parameter 



4) Path length of reflected ray 

 rd. Path length of direct ray 



R. 1) Resistance 



2) Plane-earth reflection coefficient = pe"-'* 



3) Path-difference parameter = {kaA)/{hidT) 

 /?„. Resistive component of antenna impedance 

 RH. Relative hvmiidity in per cent 



Ri- Resistive component of load impedance 



Rr. Radiation resistance of an antenna 



s. 1) Spacing between dipoles in an antenna array 



2) C'oefficient of distance for shadow factor 



3) Dimensionless coordinate = di/d 

 S. 1) Scattering cross section 



2) Area 

 S,S{u). Imaginary part of Fresnel's integral 



t. 1) Time 



2) Pulse width 



3) Degrees centigrade 

 T. Absolute temperature 



u. Dimensionless ooorilinate = ho/hi 



V. 1) Velocitj' of wave propagation = c/n 



2) Argument of Fresnel's integral 



3) Dimensionless parameter = d/dx 

 V. Voltage 



V,f Xoise voltage 



W. Power per unit area 



Wi. Incident power per unit area 



Wr- Scattered power per unit area at the receiver 



z. Amplitude of ratio of diffracted field to free-space 



field 

 Z. Impedance 



Za- Antenna impedance 



Zi. Load impedance 



a. 1) Attenuation constant, real part of propagation 



constant y 

 2) Angle made by ray with the horizontal 

 ai,a2. Angle of elevation of diffracting edge as seen from 



transmitter, receiver 

 ;8. 1) Bearing of the sun 



2) Phase constant, imaginary part of propagation 

 constant y 

 Pifii. Angle between ray from transmitter, receiver, and 



horizontal at diffracting edge 

 y. 1) Propagation constant = a -\- jfi 



2) Angle between horizontal at base of transmitter 

 and line joining transmitter base to receiver 

 7i. Angle between the direct ray and the horizontal at 



the transmitter 



Ap. 



A(Ap). 



A/. 



V- 



MO. 

 Mr- 



4>. 



4'd. 



1 ) Declination of the sun 



2) Angle of phase retardation due to path-length 



difference between direct and reflected rays 



3) Ground parameter depending on complex dielec- 



tric constant 

 Path-length difference between direct and reflected 



rays = r — r^ 

 = {2hihi)/d 



Correction factor for Ap 

 Bandwidth 



Variable used in diffraction region 

 Dielectric constant of free space 



= 8.854 X 10-1= ^ 10-9 



SGtt 

 Complex dielectric constant = tr ~ j H 

 Imaginary part of dielectric constant = (iOo-X 

 Real part of dielectric constant 



1) Phase-angle lag due to diffra(^tion 



2) Dimensionless distance variable for curved-earth 



diffraction 



1) Angle between horizontal at transmitter base 



and horizontal at point of reflection 



2) Angle of tilt of scattering cylinder 

 Wavelength 



Permeability of free space = 47rlO"' 

 Permeability relative to free space 



Angle between reflected ray an(J horizontal at trans- 

 mitter 



1) Radius of curvature 



2) Amplitude of reflection coefficient 



1) Conductivity 



2) Railar cross section 



1) Complex mode numbers 



2) Half beam-width angle 



1) Phase angle of reflection coefficient 



2) Latitude 



= 4> — IT = phase angle of reflection coefficient 



relative to a perfect reflector 

 Distance function for the first mode 



1) Phase-angle difference between currents in 



dipole-antenna arraj' 



2) Angle between direct or reflected ray and the 



horizontal at the reflection point 



3) Height variable in the diffraction region 

 Angle between direct ray aufl horizontal at reflec- 

 tion point 



Angular velocity = 2Trf 



Total phase lag between direct and reflected rays 

 = (/)' + 5 =4> — IT + 8 



