RADIO TRANSMISSION SYSTEM FOR TELEVISION 



647 



of two diamonds placed side by side with the corners just touching. 

 Images "out of frame" along the vertical axis are frequently seen on 

 the motion picture screen. 



The explanation is fairly obvious. The present more or less 

 generally accepted view of fading is that it is a manifestation of 

 transmission along two or more paths, at least one of which is variable, 

 producing a continually changing phase relationship between the 

 components and a corresponding waxing and waning of the resultant 

 signal. In the present case, the major image was probably produced 

 by the so-called "ground wave." The secondary images probably 

 resulted from components which were transmitted upward at a 

 relatively sharp angle and turned back to the receiving station from 

 the Heaviside layer, the difference in framing being due to the longer 

 time of transmission. 



n 



m 



V 



T^^ 



TELEVISION 

 SIGNAL 



TRANSMITTED 

 RADIO SIGNAL 



:^;;:u:^ 



ut^Jt^ 



■GROUND WAVE RECEIVED 



- REFLECTED WAVE 3,^^^^ 



/two components, 

 (envelopes only 



ryrvcr^prz 



rectified 

 signal 

 (radio components 

 v in phase 



RECTIFIED 

 SIGNAL 



/radio componentsN 



OUT OF phase 



F"ig. 8 — Production of positive and negative secondary images due to 

 multi-path transmission 



The production of negative secondary images is a most interesting 

 phase of the phenomena. This effect may be explained quite easily 

 by means of a series of signal diagrams such as is shown in Fig. 8. 

 42 



