Y 



ULTRA-SHORT-WAVE TRANSMISSION PHENOMENA 111 



small loop antenna is mounted in the neighborhood of the set, pre- 

 cautions being taken to keep ground reflected fields down in intensity. 

 From loop current and physical dimensions and the oscillator-receiver 

 spacing the resultant field is calculated and compared with the field to 

 be measured. 



3. Modihed short-wave method. This is the method we have chiefly 

 used and which appears at the moment to be most promising. From a 

 knowledge of the impedances of antenna and receiver input circuits, the 

 voltage transfer ratio from effective antenna input to resultant grid 

 input can be calculated for optimum power transfer conditions, and to 

 a good degree of accuracy. This factor, together with the antenna 

 effective height and overall set gain, permits a measurement of the 

 field intensity. In effect this is a variation of the Friis and Bruce 

 method. 



