Radio-frequency mixing explained
Audio mixers (as used in recording studios and radio broadcast stations) are used to add or ‘balance’ the signals from various sources such as microphones, CD players, etc. These have nothing whatsoever to do with radio-frequency (RF) mixers, and should never be confused with them.
RF mixers and beat frequencies
Instead of adding signals (as in the audio mixer), the RF mixer multiples them together. As you might expect, this has an entirely different effect. The two signals entering ...