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BELL SYSTEM TECHNICAL JOURNAL 



which is necessary for the changing of wavelengths, very unhandy, and 

 hence the crystal control and amplifier system, except the last stage 

 is provided in duplicate, one side being used for the longer and the other 

 for the two shorter waves. Wave changing, except for the output 

 circuit of the power stage, is then accomplished by connecting the 

 proper amplifier to the power stage. 



The quartz plates used in the crystal control system are circular, 

 being approximately one inch in diameter, and are clamped rigidly in 

 the holder. This clamping serves to prevent any change of frequency 

 with mechanical vibration. The holder with its crystal is mounted in 

 a small oven, the temperature of which is held constant at 50 deg. cent, 

 to better than ±0.1 deg. cent. The thermal system of this oven is so 



CRYSTAL 

 AND OVEN 



5 WATT 

 OSCILLATOR 



7j WATT 

 AMPLIFIER OR 

 HARMONIC GENERATOR 

 LJ 



50 WATT 

 AMPLIFIER 



500 WATT 

 POWER AMPLIFIER 



Fig. 1 1 — Ship transmitter's schematic diagram. 



designed that the change of internal oven temperature with tempera- 

 ture changes of the surrounding air is negligible. 



As shown in the figure, the crystal is connected between the grid and 

 filament of a 5-watt vacuum tube which, together with the parallel 

 resonant circuit connected to the output of this tube, forms the crystal 

 oscillator. The radio-frequency voltage developed by the crystal oscil- 

 lator is applied directly to the grid of a 7>^-watt screen-grid tube which 

 can be used either as an amplifier or a frequency doubler. The output 

 of this tube, except in the case of the higher frequencies, is applied 

 directly to the grid of a 50-watt screen-grid amplifier. For the higher 

 frequencies a second frequency doubler can be switched into the circuit. 

 The output of the 50-watt tube is coupled through a balanced trans- 

 former to the final amplifier stage. The amplifier or frequency doubler 



