Modulation is the Method the transmitter uses to send the data containing

the position of the sticks to the receiver.

Although there are several types of transmission system The signal transmitted to the servos has not changed since the early days of R/C

Each servo channel consists of a pulse which is varied by the stick associated

with that channel. This pulse varies from 1 millisecond to 2 millisecond (1.5 being centre position)

This is repeated for each servo channel every 20 ms (50 times a second)



                                   Modulation Methods

AM: Stands for Amplitude Modulation which transmits by a variation in the

         amplitude of signals. In R/C it basically switches the transmitted signal

        off and on. It is subject to interference more than FM. Mostly found

        on 27 MHz sets.

                              AM transmitter output

FM: Stands for Frequency Modulation which transmits signals by varying

        the  frequency of the transmitted signal ,this  reduces the risk

        of "glitches" due to signal interference making it preferable to AM.

The 2GHz transmitters use a different Transmission  system (see 2GHz system) although the output to the servos is the same as the previous systems