THE BRIDGE STABILIZED OSCILLATOR 



583 



Experiment 



The circuit diagram of an experimental bridge stabilized oscillator is 

 shown in Fig. 3, and its photograph in Fig. 4. The amplifier unit 

 consists of a single high-mu tube Fi with tuned input and output 

 transformers T\ and Ti and the usual power supply and biasing 

 arrangements. The crystal, mounted in the cylindrical container at 

 the left end of the panel, is one having a very low temperature coeffi- 

 cient of frequency at ordinary ambient temperatures. In Fig. 4 it is 

 shown without provisions for temperature control. A high Q is 

 obtained by clamping the crystal firmly at the center of its aluminum- 



TO 

 8 < LOAD 



Fig. 3 — Circuit of experimental bridge oscillator. 



coated major faces between small metal electrodes ground to fit, and by 

 evacuating the container. 



Some of the circuit parameters are listed below : 



Ri = Tungsten-filament lamp, 



Ri = 100 ohms, 



i?3 = 150 ohms, 



Zi = 100 kc. crystal. 



Characteristics at resonance : 

 Ri = 114 ohms, 

 Xl = Xc = 11,900,000 ohms, 

 Q = 104,000, 

 R5 = Re — 150 ohms (approx.), 

 Ri = 500 ohms, 

 Rs = 200 ohms, 

 \n\ = 422 (52.5 db voltage gain from e to E). 



