Chapter 2 

 TRANSMISSION EXPERIMENTS NEAR SAN DIEGO 



2 1 ONE-WAY TRANSMISSION EXPERI- 

 MENTS OVER THE SEA BETWEEN 

 LOS ANGELES AND SAN DIEGO- 



ONE-WAY TRANSMISSION tcsts have beeii made by 

 two methods : over a fixed path and by means of 

 an airplane to sample vertical distribution of field 

 strength. The fixed path is a nonoptical over-water 

 path, §0 nautical miles in length from San Diego to 

 San Pedro near Los Angeles Harbor. No intervening 

 landscape is present at either end of the path. The c-w 

 transmitters are located at the San Pedro end of the 

 p)atli at 100-ft elevation and operate on frequencies 

 of 53, 100, 547, and 3,200 mc. The latter frequency 

 has just recently been added, and insufficient data 

 have been obtained to include in tins report. The trans- 

 mitters are quite conventional, the 53 mc being crystal 

 controlled and the other two being self-excited \uiits 

 in which adequate frequency stability has been ob- 

 tained by use of high-(? circuits. Monitors, which are 

 read periodically, are provided on each transmitter. 

 The receiver location, at 100-ft elevation, is located 

 on Point Loma, San Diego, near the laboratory. The 



'By L. G. Trolese, U. S. Navy Radio and Sound Labo- 

 ratory, San Diego, California. 



receivers are of standard construction incorporating 

 a balanced d-c amplifier and Esterline-Angus recorder 

 in the output circuit. Filament and plate voltages are 

 regulated. Detuning effects due to temperature changes 

 are minimized by temperature regulation in the re- 

 ceiver house. Receivers are calibrated at least once 

 each week. 



Four receivers have been installed in a PBY-5A 

 plane which is used to sample vertical sections of field 

 strength distribution at various distances up to 130 

 miles from the transmitters at 100-ft elevation. The 

 frequencies used ..are 63, 170, 5:24, and 3,350 mc. 

 Certain precautions wci'c found necessary to insure 

 correct orientation of transmitting antennas on the 

 ground and receiving antennas on the plane. Receiving 

 antennas on the ]ilane are fixed in position, and meas- 

 urements are taken only with the plane flying toward 

 the transmitters. The plane's orientation is controlled, 

 and the distance from transmitters determined, by 

 utilizing the plane's Type ASE (Admiralty Signal Es- 

 tablishment) radar to home on a beacon located near 

 the transmitters. All four transmitters and transmit- 

 ting antennas are installed on a single rotating mount. 

 A direction finder system also installed on the rotat- 

 ing assembly and operating on the plane's radar fre- 



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Figure 1. Maximum received signal versus atmospheric refraction. 



19 



