transmitting direction. The transducer is a Navy-type QBG crystal 

 unit, which, because of its size, shows directional characteristics 

 and power gain. It was chosen because of these characteristics, and, 

 although its resonant point lies at about 26 kc., it wa3 thought that 

 sufficient energy would be radiated over the desired range (21 to 

 36 kc.) if it were fed at 150 ohms impedance. The 26 kc. high- 

 efficiency point would be near the proposed optimum operating depth 

 (100 fathoms). 



Waveforms 



A reproduction of two polaroid oscilloscope photographs are shown 

 in figures 3 and 4. The first photograph (fig. 3) shows modulated 

 waveforms j the second photograph (fig. 4) shows carrier and modulating 

 waveforms. 



Fig, 3» Sample modulated wave— Fig, 4* 



form signals . 



Carrier waveform signal 

 (above) modulating wave 

 form signal below. 



The top modulated waveform (fig, 3) was taken at point D, the 

 driver grid, and measured 9»5 volts peak-to-peak. The second modu- 

 lated waveform (fig. 3) was taken at point E, across the secondary 



