PROPAGATION IN S AND X BANDS IN LOW-LEVEL OCEAN DUCTS 



35 



fliglits and a guy rigging nmniiig from tlie water's 

 edge to 10 ft above the top of the tower. Detailed 

 soundings in the first 100 ft were tlien taken by slid- 

 ing the measuring instruments up and down the 

 rigging. Since the duct conditions important in this 

 investigation were alwavs below 100 ft. onlv ocea- 



A typical procedure was to align tlie ship at a point 

 about 6 miles off shore (closer ranges were impossible 

 Ijecause of reefs lying off the northeastern coast of 

 the island) and commence a run on a prescribed 

 bearing away from the tower. This bearing was pre- 

 deternnned by ship oliservations of the current wind 



20 



40 



60 



80 



100 



120 



140 



160 



FiGUHE 2. S-band run in, March 19 to 21, 1945. Signal strengths of various antenna combinations compared to free 

 space level. 



sional kite soundings (two to three a day) were made 

 to check the higher levels. Most of the data accumu- 

 lated were taken on the tower rigging where detailed 

 soundings could be made. Wind speeds at the surface 

 and 100 ft levels were recorded hourly. Hygrother- 

 mographs were placed at the antenna levels and con- 

 tinuous records taken to determine the diurnal varia- 

 tion of temperature and relative humidity, if any. 



and sea direction. The receiving antennas were 

 aligned to maximum signal strengths recorded by the 

 receivers and secured in this position by clamping to 

 the deck. The ship operating speed was usually around 

 10 knots, depending on the current sea conditions. 

 While the ship was moving on the course, antenna 

 changes on the receivers were made every 15 minutes 

 for some runs, while antenna heights on the trans- 



