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



37 



Figures J, 'i, o, and -I: show the plots i'or one com- 

 plete run. It is apparent that the lower antenna com- 

 hinations on X band produced the highest signal level. 

 Signal strengths from higher antenna combinations 

 declined proportionately with height. On S band the 

 re\erse appeared to be true, the -16- to 94-ft antenna 



tion. This clearly shows that the highest combination 

 available with this setup produced the best results. 

 It can also be seen that the signal level is considerably 

 further below the free space value than is the X-band 

 signal for these ranges. 



In order to determine tlie effect on the siffnal 



20 



40 



60 



80 



100 



120 



140 



160 



FiGUKE 4. X-band run in, March 19 to 21, 1945. Signal strengths of various antenna combinations compared 

 to free space level. 



combination giving the highest average signal level. 



Figure 5 shows a composite presentation of 16-ft 

 transmitting antenna to 14-ft receiving antenna. The 

 average received signal with this antenna combina- 

 tion is 5 to 10 db below the 8- to 6-ft X-band antenna 

 combination. 



Figure 6 is a record of all the runs on the iG-ft 

 transmitting and 94-ft receiving antenna combina- 



strength of moving the anteniui inland, a mobile unit 

 consisting of an X-band receiver, test set, recorder, 

 and 18-in. parabolic dish were mounted in a truck 

 and operated from a gasoline-driven generator. Meas- 

 urements during several runs were recorded l^, Va, 

 and 1 mile inland from the tower. The antenna heights 

 above the sea surface were 35, 50, and 100 ft, respec- 

 tively. In one instance, the unit was placed behind a 



