REFLEX OSCILLATORS 



613 



originally intended to design this transducer so that all elements would be 

 fixed. It was found, however, that an adjustable back piston setting per- 

 mitted compensation for manufacturing tolerances in the tubes as well as 

 permitting the presentation of a better impedance to the oscillator over the 

 band than was attainable with a fixed transducer. This is illustrated in 

 Fig. 102 which shows the power output versus frequency for a typical 2K54 

 and a typical 2K55 as a function of frequency for three cases. In one case, 

 as shown by curve B, the power output is delivered at all frequencies into 

 the optimum impedance, i.e. the impedance into which the oscillator will 

 deliver maximum power. Curve A shows the power output delivered into 



■REQUIRED RANGE 



- REQUIRED RANGE 



4200 4300 4400 4500 4600 4700 4600 4900 



FREQUENCY IN MEGACYCLES PER SECOND 



fig. 102. — Peak power output vs frequenc\- for the 2K54 and 2K55 oscillators for sev- 

 eral load conditions. Curves A give the performance obtained when the tubes operate 

 into a characteristic admittance load threugh the coupling of Fig. 101 with the end plate 

 fixed so that the admittance presented to the tubes is constant to within 1 db over the 

 frequenc}- range. Curves B give the performance obtained when the optimum imjjedance 

 is presented to the oscillators throughout the band. Curves C give the performance ob- 

 tained when the tubes are coupled to a characteristic admittance load with the coupling 

 unit of Fig. 101 and with a back piston adjusted to the best value at each frequency. 



a transducer which has the back piston fixed at a distance from the probe, 

 so chosen that the impedance seen by the oscillator is fiat over the band to 

 within 1 db. Curve C shows the power output when the back piston of the 

 transducer is adjusted so that the tube delivers maximum power. It can 

 be seen that the performance obtained under the latter circumstances is very 

 nearly as good as that obtained when the optimum impedance is presented 

 to the oscillator. 



Froon Sections III and IX we would expect that, since the coupling system 

 is such as to give maximum power throughout the band, the sink margin 

 should be slightly greater than 2. Figures 103 to 106 give impedance per- 

 formance diagrams for 2K.S4 and 2K55 at the four transmitting frequencies 



