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BELL SYSTEM TECHNICAL JOURNAL 



Radio Receivers 

 Both receivers were high fidehty (7000 cycles) units of the tuned 

 radio frequency type. One of these was modified so that either man- 

 ual or automatic volume control could be used, and the level impressed 

 upon the detector was reduced so that it would function as a strictly 

 square law device. The cathode resistor which normally furnishes 

 a grid bias for the detector tube was replaced by a battery. This was 

 necessary in order to prevent straightening out of the characteristic 

 by degeneration at very low frequencies. In Fig. 3 is shown a plot of 



5 10 20 30 40 50 100 200 300 500 



IMPRESSED ALTERNATING VOLTAGE IN ARBITRARY UNITS 



Fig. 3 — -Characteristic of radio frequency amplifier and square law detector. 



the change in detector space current as a function of the impressed 

 voltage. It will be observed that for increments of less than 200 ^A 

 the characteristic has a slope of two to one. All observations were 



