The Radio Control System
All standard radio systems consist of four (4) basic components. Transmitter - The unit that takes the control input from the pilot through the gimbal mounted sticks, encodes this input and sends it to the aircraft as a radio signal.
Receiver - The unit that receives the signal from the transmitter, decodes it and routes it to the appropriate servo.
Servos - These devices convert the decoded signals into a mechanical force that is directed via a linkage to the appropriate control surface.
Batteries - The component that provides the electrical supply enabling the other components to function.
Radio Control Transmission Frequencies The atmosphere surrounding the earth is filled with a myriad of radio signals providing information for thousands of different communication systems along with naturally occurring radio waves such a solar radiation. When you switch on your radio control transmitter you merely add to this information blitz. It is therefore essential that the signals you transmit do not coincide with other transmitted signals or are, at the very least, stronger than any other similar signal within the vicinity of your flying field. Your airborne receiver would otherwise have great difficulty deciding which signal to obey. Specific frequencies are assigned for use with airborne R/C models. A beginner must ensure that the system he chooses is tuned to one of these frequencies. Radio control system manufacturers usually place a sticker on the outside of the carton that says, "For airborne use only". There is a frequency reference chart available that lists the purposes of all of the frequencies that are assigned for R/C use. The radio system that is chosen must meet the 1991 specifications for narrow band receivers. It is the responsibility of the manufacturer to ensure the equipment is certified to this standard. The owner's manual for the system will note that the requirements are met and many of the transmitters and receivers will have a gold sticker to signify this fact.
Radio control systems may transmit and receive on either an Amplitude Modulated (AM) signal or a Frequency Modulated (FM) signal. Most modern aircraft control systems use FM frequencies as they are less prone to interference than the AM frequencies. Having said that, AM systems seldom have problems with interference. Some radio systems use an internal system, called PPM, to help to nullify interference.
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