TRANSATLANTIC RADIO TELEPHONY 327 



^here 



Ilg = Effective height of the wave-antenna referred to the char- 

 acteristic impedance (kilometers) 



E' = The potential gradient of the vertical component of the 

 impressed field (volts per kilometer) 



Ek = The electromotive force introduced in series with the char- 

 acteristic impedance at the initial end of thewave-antenna 

 producing the same cuirent at the distant end as the 

 impressed field (volts) 



4. Quasi-tilt Angle and Ground Resistivity. The measured effective 

 height of a wave-antenna is a function of four constants: 



1. The length of the antenna; 



2. The height of the antenna; 



3. The propagation constant of the antenna; 



4. The ratio of the component of the electric wave parallel to the 



surface over which the antenna is constructed to the vertical 

 component of the electric wave. 



In general, the first three of these constants are different in value for 

 antennas constructed at different locations, but they may be varied 

 over a limited range by changing the construction and dimensions of 

 the wave-antenna. The comparison of effective heights, therefore, 

 does not readily yield information regarding the relative suitability 

 of various locations for wave-antenna systems. The ratio of the 

 horizontal component to the vertical component of the impressed 

 field is, however, a constant whose value is dependent solely upon the 

 ground conditions at the location (assuming a fixed frequency for the 

 comparison). 



In case the time phase between the horizontal component and the 

 vertical component of the impressed field were zero, the ratio of these 

 two components would represent the tangent of the angle of forward 

 inclination of the propagated wave front. In general, the phase angle 

 between the two components is not zero, so that such a simple relation 

 does not hold. It is convenient, however, to call the ratio ot the two 

 components of the impressed field the tangent of the "quasi-tilt 

 angle," where the "quasi-tilt angle" becomes the real tilt angle in 

 the limiting case. 



In terms of the effective height, the antenna constants, and the 

 vertical component of the impressed field, the current produced at the 

 far end of the wave-antenna is (using the nomenclature of Appendix 1 

 and to the same degree of approximation as equation (12)): 



