| 摘要 |
A tuned transistor oscillator for use with an RF receiver includes a transistor amplifier having a tuned network coupled between the collector and base of the transistor. Feedback is provided by a capacitor coupled between the tuned network and the emitter of the transistor. The tuned network includes a transmission line, a variable capacitive reactance means in parallel therewith, a first variable capacitance diode in series with said reactance means, and a second variable capacitance diode serially connected to said line. The capacitance of said reactance means is varied to allow the oscillator to sweep the desired frequency range, and the first and second capacitance diodes are varied by a DC AFC (automatic frequency control) voltage provided by the discriminator of the RF receiver to prevent oscillator drift. Said first and second diode capacitances are arranged so that the first capacitance has its greatest effect at the lower end of the oscillator frequency range while the second capacitor has its greatest effect at the upper end of said range, thereby providing an AFC signal which varies the oscillator frequency by a substantially constant amount independently of the oscillator frequency.
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