 For example, to pick up a signal at 1500 kHz the local oscillator would be tuned to 1450 kHz.Mixing the two created an intermediate frequency of 50 kHz, which was well within the capability of the tubes.The name "superheterodyne" was a contraction of "supersonic heterodyne", to distinguish it from receivers in which the heterodyne frequency was low enough to be directly audible, and which were used for receiving "continuous wave" (CW) Morse code transmissions (not speech or music).