REFLEX OSCILLATORS 



609 



the thermal time constant of the grids, then the peak power input to the 

 oscillators may be increased over the continuous limit by the duty factor, 

 provided that the voltages applied are consistent with the insulation limits 

 of the tubes and that the peak currents drawn from the cathode are not in 

 excess of its capacity. 



An application for a pulsed oscillator arose in the AN/TRC-6 radio 

 system/'' This was an ultra-high frequency military communication system 

 using pulse position modulation to convey intelligence. With the high gain 

 which may be achieved with antennas in the centimeter range, the power 

 necessary in the transmitter for transmission over paths limited by Hne of 

 sight is of the order of a few watts peak. In beating oscillator applications 

 the power output is of secondary importance to electronic tuning, so that 

 the reflex oscillators previously described were designed to operate with a 

 drift time in the repeller space such as to provide the desired tuning. In a 



REPELLER --■»■ 



\ INNER"RESONATOR" 



\ -- -^ DECOUPLING SECTION^ J 



'OUTER NON-CRITICAL PORTION OF RESONATOR^ 



Fig. 98. — The resonator and repeller structures of the oscillator shown in Fig. 97. 



pulsed transmitter electronic tuning is unnecessary and indeed undesirable, 

 since it leads to frequency modulation on the rise and fall of the pulse. In 

 section III it is shown that for maximum efficiency with a given resonator 

 loss there will be an optimum value for the drift time. If there were no 

 resonator loss this time would be f cycles, which is the minimum possible. 

 By utilizing the optimum drift angle and taking advantage of the higher 

 peak power inputs permitted by pulse oscillator it was possible to obtain 

 peak power outputs of the order of several watts using the same structure 

 as employed for the beating oscillators previously described without exceed- 

 ing the power dissipating capability of such a structure. From the stand- 

 point of military convenience this was a very desirable situation for reasons 

 of simplicity of tuning and ease of installation. 



^^ A Multi-channel Micro-wave Radio Relay System, H. S. Black, W. Beyer, T. J. 

 Grieser, and F. \. Polkinghorn, Electrical Engineering Vol. 65, No. 12, pp. 798-806, Dec. 

 1946. 



