ULTRA-SIIORT-WA VE TRA XSMISSIOX PHENOMENA 



215 



lamp cord for it. In raising and lowering the antenna this transmission 

 line was simply permitted to pile up on the ground. The antenna 

 ammeter showed only small current variations as this coil was handled 

 or pushed about. We originally had some doubts as to whether this 

 hill would give a clean-cut reflection since the surface in the receiver 

 direction was somewhat undulating and had a gully with trees be- 

 ginning some 200 feet down the hillside. However, as the results 

 indicate, a fairly definite reflection component is produced. 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 



MILES FROM TRANSMITTER 



•Fig. 15— Flight from transmitter. Altitude — 8000 feet; 

 wave-length — 4.3 meters, June 24, 1931. 



The dots in Figs. 13 and 14 are observed values, the full lines are 

 theoretical curves. These latter were obtained by taking the hill con- 

 stants the same as for the McCatharn Hill, but the hill itself was not 

 assumed to be a plane. Instead, by graphical plotting from the hill 

 contour, the tangent plane for each antenna height was located and 

 used for the calculation for that height only. The resulting curve is a 

 somewhat better fit than is obtained by averaging the hill to a common 

 plane. 



This hill surface, as stated earlier, is a rather poor fit to a plane (the 

 profile cross section shows the hill up too favorably) and has quite a 



