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English: Diagram of an Armstrong oscillator circuit using a FET as the active device. The Armstrong oscillator, invented by Edwin Armstrong in 1913, was one of the earliest oscillator circuits. It is an LC oscillator, in which the frequency is determined by a tuned circuit consisting of the inductor L1 and capacitor C.
The Armstrong oscillator [1] (also known as the Meissner oscillator [2]) is an electronic oscillator circuit which uses an inductor and capacitor to generate an oscillation. The Meissner patent from 1913 describes a device for generating electrical vibrations, a radio transmitter used for on–off keying. Edwin Armstrong presented in 1915 some ...
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For AM reception, the gain of the loop is adjusted so it is just below the level required for oscillation (a loop gain of just less than one). The result of this is to greatly increase the gain of the amplifier at the bandpass frequency (resonant frequency), while not increasing it at other frequencies.
The Armstrong method generates a double sideband suppressed carrier signal, phase shifts this signal, and then reinserts the carrier to produce a frequency modulated signal. Frequency modulation generates high quality audio and greatly reduces the amount of noise on the channel when compared with amplitude modulation .
A voltage-controlled crystal oscillator (VCXO) is used for fine adjustment of the operating frequency. The frequency of a voltage-controlled crystal oscillator can be varied a few tens of parts per million (ppm) over a control voltage range of typically 0 to 3 volts, because the high Q factor of the crystals allows frequency control over only a ...
All these early technologies were superseded by the vacuum tube feedback electronic oscillator, invented in 1912 by Edwin Armstrong and Alexander Meissner, which used the triode vacuum tube invented in 1906 by Lee de Forest. [1] Vacuum tube oscillators were a far cheaper source of continuous waves, and could be easily modulated to carry sound ...
Pearson-Anson oscillator circuit. The Pearson–Anson effect, discovered in 1922 by Stephen Oswald Pearson [1] and Horatio Saint George Anson, [2] [3] is the phenomenon of an oscillating electric voltage produced by a neon bulb connected across a capacitor, when a direct current is applied through a resistor. [4]