A heterodyne is a signal frequency that is created by combining or mixing two other frequencies using a signal processing technique called heterodyning, which was invented by Canadian inventor-engineer Reginald Fessenden. Heterodyning is used to shift signals from one frequency range into another, and is also involved in the processes of modulation and demodulation. The two input frequencies are combined in a nonlinear signal-processing device such as a vacuum tube, transistor, or diode, usually called a mixer.
In the most common application, two signals at frequencies f1 and f2 are mixed, creating two new signals, one at the sum of the two frequencies f1 + f2, and the other at the difference between the two frequencies f1 ? f2. The new signal frequencies are called heterodynes. Typically, only one of the heterodynes is required and the other signal is filtered out of the output of the mixer. Heterodyne frequencies are related to the phenomenon of "beats" in acoustics.
A major application of the heterodyne process is in the superheterodyne radio receiver circuit, which is used in virtually all modern radio receivers.
Rife and Gallart suggest that we review this idea:
2. Heterodyning Light
We will first explain the term “heterodyne” and then show its application to light as developed by Rife. It is an observed fact in physics, and a principle constantly used in radio and in work with sound, that when two different frequencies of vibration are produced, they inter-act upon each other to produce two new frequencies- one of them is the sum of the two original or fundamental frequencies: The other is the difference between the two originating or fundamental frequencies. Suppose, for example, that in the range of sound, a tone of 400 cycles per second and another tone of 600 cycles per second is produced. The resulting frequencies will then be 200 cycles, the difference between 400 and 600 cycles, and 1,000 cycles for the other new tone, the sum of 400 and 600 cycles.
So far as is known, Rife was the first individual to apply this principle to the field of light.
[Mark L. Gallert, The Royal Rife Report]
See Also
Additive and Subtractive Synthesis
Beat
Power of Beat Harmonics