AMPLITUDE MODULATION (A.M.)

The modulation of the amplitude of an R.F. wave or Carrier wave (having a higher frequency), based on the amplitude of the A.F, (having lower frequency) is termed as Amplitude Modulation.

The superimposing of both waves is generally by mixing the two waves and their values in the form of either

R.F. + A.F.

or

R.F. -A.F.

Since the value of R.F./Carrier freq. is always greater than A.F.

The changes to wave due to modulation is always carried out on the upper side band, but to increase the efficiency, a component is used which generates a mirror image of the upper side band, thus creating a double side band wave.

For example: The H.F. channel used in aircraft uses Single side band & the VHF channel uses Double Side band.