Parallel-Network Oscillators

A parallel-network oscillator is a two-path oscillator with the gains of the two paths varied symmetrically about a mean value by means of control voltages. The result is a wide-range, electrically tunable, low-level oscillator. Design fundamentals and considerations relating to different types of such oscillators are discussed and analyses made of the two principal types. The tuning ratio of one of the types is limited to about two-to-one and that of the other is limited to a frequency coverage rather than any specific tuning ratio -up to about half the gain-bandwidth product of the tubes employed. The amplitude of oscillations is relatively constant over the major portion of the tuning characteristics. Stability, waveform, and noise are also discussed. Two examples are given, one of which makes use of a single twin-triode tube without amplitude stabilization which covers a range of about 15 to 24 mc. The second example uses four pentodes and covers a range of about 15 to 43.5 mc. Finally, some of the future possibilities of parallel-network oscillators are mentioned.