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BELL SYSTEM TECHNICAL JOURNAL 



phenomena were studied in both directions between a fixed location 

 on a- building and the mobile laboratory. 



Apparatus 



Both terminals employed vertical half-wave antennas which were 

 connected to balanced circuits by means of symmetrical two-wire 

 transmission lines. At the fixed locations unloaded antennas were 

 used ; at the mobile terminal, in order to limit their heights to eight 

 feet above the ground and maintain the symmetry the antennas were 

 loaded so that their lengths were reduced to about a quarter of a 

 wave-length (Fig. 1). 



. \±i&-imi^mumM^^. 



Fig. 1 — Mobile receiving equipment. 



The transmitter consisted of an electric oscillator employing two 

 75-watt tubes operating in push-pull relationship. At the fixed 

 location, where ample power was available, the transmitter was capable 

 of producing one ampere ^ of 100 per cent modulated carrier in its 

 antenna without undue distortion. The mobile transmitter which 

 used a dynamotor for tube plate supply was capable of producing the 

 same current in its antenna. This corresponds to about six decibels 

 less power due to the shorter antenna length. 



The measuring set was of the double detection type with balanced 



high-frequency circuits, push-pull first detector and calibrated inter- 



2 The current was measured b>' a Weston t)pc 425 thernioammeter at the current 

 niaxinmm. 



