HIGH ACCURACY HETERODYNE OSCILLATORS 419 



by the modulator and amplifier; and the top by the power pack. Per- 

 forations in the oscillator cover provide ventilation to reduce warm- 

 ing-up effects. A close-up giving the details of the scale mechanism 

 and the shielding is shown on Fig. 5. 



Fig. 5 — Details of the scale mechanism. 



Tests on the oscillator show that the overall frequency accuracy 

 throughout its range can be maintained to dz 25 cycles. The har- 

 monics are down 40 db from the fundamental at 100-milliwatt output. 

 With the full output of one watt the harmonics are 30 db down. The 

 total output variation with frequency is shown on Fig. 3. 



This oscillator has found a wide range of applications as an accurate 

 source of frequency in the communications field. 



List of Symbols 



F output frequency of the heterodyne oscillator 

 Fo standard frequency used to check the oscillator at the 

 low end of the scale 



