ULTRA-SIIORT-WAVE TRANSMISSIOX PHENOMENA 



209 



striking reradiation phenomena. Nearby planes gave field variations 

 up to two decibels in amplitude, and an airplane flying over the 

 Holmdel laboratory and towards this landing field was detected just as 

 the Holmdel operator announced "airplane overhead." These were 

 all fabric wing planes. If the reradiation field to which such an air- 

 plane is exposed is of inverse distance amplitude type while the 

 directly received ground fields are of more nearly inverse distance 

 square type, as in Fig. 2, it is easy to see that at five miles an overhead 

 airplane is exposed to a field intensity about ten times (20 decibels) 

 that existing at the ground, and for ordinary airplane heights a high 

 energy transformation loss in the reradiation process can occur and 

 still give marked indications in the receiver meter. This airplane 

 reradiation was noticed at various subsequent times, sometimes when 

 the airplane itself was invisible. A set of theoretical beat frequency 

 versus distance curves are given in Fig. 7. 



Air-Line Transmission 



While ordinary ultra-short-wave transmission is complicated by 

 local reradiations and diffraction phenomena these should become 

 relatively innocuous for favored locations such as hilltop-to-hilltop 

 transmissions with the air-line path between them clearing all inter- 

 vening obstacles. Here the presence of fading, day-to-night changes in 

 transmission, amount of static interference, and the role of the earth- 

 reflected radiations should be determinable. After some days of rough 

 surveying such a pair of hilltops was found 39 miles (63 kilometers) 

 apart. We would have preferred a greater distance but none such 

 could be located with certainty, with one of the hills necessarily local. 



The transmitter was mounted on this local hilltop, Beer's Hill, two 

 miles (3.2 kilometers) air line to the north northwest of the laboratory. 

 The apparatus consisted of a 40-foot (12.2-meter) lattice mast with 

 nonmetallic guys, mounting a half -wave linear antenna which could be 

 rotated between a vertical and a horizontal position. A low im- 

 pedance (246-ohm) transmission line, similar to the one earlier de- 

 scribed, carried the ultra-short-wave current from the generator 

 shack at the foot of the mast to the antenna itself. The termination 

 and method of antenna current indication were as described for the 

 Holmdel laboratory transmitter. The hilltop altitude (U. S. Bench 

 Mark) was 343 feet (104.6 meters) and the antenna was thus 383 feet 

 (116.8 meters) above sea level. 



The receiver site was located on a hill spur on the P. K. McCatharn 

 farm 2| miles north of Lebanon, N. J., and at an altitude of 750 feet 

 (228.5 meters). Taking the altitudes from the New Jersey geological 



