Abstract
AN article on this subject by I.E. Fair (Bell Lab. Rec., £\ 21, No. 8; April, 1943) points out that stability is one of the major requirements for oscillators controlling the frequency of radio transmitters. In ultra-high-frequency transmitters it assumes particular importance because a very small percentage change hi the frequency of the controlling oscillator may shift the transmitted band many thousands of cycles. At 100 me., for example, a 0-01 per cent change in frequency means a change of 10 kc., which is as much as the entire width of a broadcast band. Stability in oscillators is secured by some form of toned circuit. The reactance of such a circuit changes slowly with frequency except over a narrow band in the region of resonance, where a small change in frequency is accompanied by a very large change in reactance, this latter enabling the resonant circuit to act as a frequency stabilizing element. Quartz crystals are eminently suited to control in this way because of their very sharp resonance, which is due to their low values of coupling and dissipation. Their characteristics change only slightly with variations in temperature and voltage, and thus high stability under all conditions is more easily obtained with them than with elements having higher dissipation or greater sensitiveness and voltage.
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HIGH CRYSTAL HARMONICS FOR OSCILLATOR CONTROL. Nature 152, 363–364 (1943). https://doi.org/10.1038/152363b0
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DOI: https://doi.org/10.1038/152363b0