Frequency Oscillator

 A frequency oscillator is an active RF component with a sole purpose to produce a perfect sine wave at a predetermined frequency.

Variable-frequency oscillator

VFO is an acronym for Variable Frequency Oscillator.

A variable frequency oscillator is needed in any radio receiver or transmitter that works by the superheterodyne principle, and which can be tuned across various frequencies. Altering the frequency of the VFO will control the frequency to which the radio is tuned.


Why do radios need a VFO?
In a simple superhet radio receiver, incoming radio frequencies from the antenna are made to mix (or multiply) with an internally generated radio frequency from the VFO in a process called mixing.

The mixing process can produce a range of output signals:

at all the original frequencies,
at frequencies that are the sum of each two mixed frequencies
at frequencies that equal the difference between two of the mixed frequencies
at other, usually higher, frequencies.
If the required incoming radio frequency and the VFO frequency were both rather high (RF) but quite similar, then by far the lowest frequency produced from the mixer will be their difference. In very simple radios, it is relatively straightforward to separate this from all the other spurious signals using a filter, to amplify it and then further to process it into an audible signal. In more complex situations, many enhancements and complications get added to this simple process, but this mixing or heterodyning principle remains at the heart of it.

There are two main types of VFO in use: analogue and digital.

Use of  Frequency Oscillator

High-frequency oscillators are used in communications equipment to provide tuning and signal-detection functions. Radio and television stations use precise high-frequency oscillators to produce transmitting frequencies.

Simple audio-frequency oscillators are used to create tones in push-button telephones. Audio tones generated by oscillators are also found in alarm clocks, radios, electronic organs, computers, and warning systems. High-frequency oscillators are used in communications equipment and by radio and television stations to produce transmitting frequencies.

Also Read: YIG Oscillator, RF Oscillator, Harmonic Oscillator, Crystal Oscillator Circuit, Frequency Oscillator, Transistor Oscillator, Electronic Oscillator, Quartz Oscillator, Microwave Oscillator, Quartz Crystal Oscillator, Yig Filter