. The Bell System technical journal . mple vertical rod antenna was thrust out of the airplane cabinceiling. This limited the maximum range which was attained, but an-tennas of greater effective height were difficult to construct. Thisplane was the Laboratories Ford trimotor, and we are indebted to M. Ryan and his staff for their cooperation in this work. Themanual recorder already mentioned was used throughout the runs,which were made by flying directly from Beers Hill to Easton, Pa., and ULTRA-SIIORT-WAVE TRANSMISSION PHENOMENA 217 then veering slightly to the left to follow the main N
. The Bell System technical journal . mple vertical rod antenna was thrust out of the airplane cabinceiling. This limited the maximum range which was attained, but an-tennas of greater effective height were difficult to construct. Thisplane was the Laboratories Ford trimotor, and we are indebted to M. Ryan and his staff for their cooperation in this work. Themanual recorder already mentioned was used throughout the runs,which were made by flying directly from Beers Hill to Easton, Pa., and ULTRA-SIIORT-WAVE TRANSMISSION PHENOMENA 217 then veering slightly to the left to follow the main New York-to-Chicago airplane route. Flights were made at 8000, 5000, 2500, and1000 feet (2440, 1525, 763, and 305 meters) above sea level, and theresults are given in Figs. 15 to 20 inclusive. Fig. 21 gives a map ofthe country. In these figures the experimental curves are supplemented by the-oretical ones, these latter being calculated by assuming the earth at thereflection point to be equivalent to a plane surface medium of a dielec-. 10 20 30 40 SO 60 70 80 90 100 110 120 130 140 150MILES FROM TRANSMITTER Fig. 17—Flight from transmitter. Altitude—5000 feet;wave-length— meters, June 29, 1931. trie constant 10 and a resistivity of 10,000 ohms per cm. cube and 100feet (30 meters) above sea level. This point, for the outermost deepminimum, varied in location from miles out, for the 1000-foot flight,to 2 miles out, for the 8000-foot flight, with corresponding angles ofincidence of 88 and degrees. The area involved is fairly level andopen. The earths curvature is taken into account and refraction cor-rections are applied using the Schelleng, Burrows, and Ferrell shown in Fig. 15 the fit at the extreme distances is considerably im-proved by this latter correction, thus indicating its validity. The deep 218 BELL SYSTEM TECHNICAL JOURNAL and outermost minimum is due to the middle distance reflection with a540-degree phase difference. It is unmistakable and
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