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About remote control model transmitters and resceivers
In order to control a RC mode� vehicle there must be a transmittor that is used to perform the controle operations. The transmittor sends commandoes to the vehicle, and it resceives feedback from the vehicles about the state of the vehicle.
There must also be a resceiver inside the vehicle. The resceiver resceives commands from the transmittor, it sends back information about the state of the vehicle and it sends signals out to the stearing components of the vehicle and the motor to performs actions.
The transmitter and resceiver together is often called a controller.
The signals going between the transmittor and the resceiver can be analog or digital. By digital units, both the resceiver and transmittor can have a whole computer inside, and can thus send and resceive a lot more complex commandos than analog transmitters and resceivers.
The commands and state signals going between resceiver and transmittor are carried by radio waves. The frequency used varies, but have to abide to govermet regulations regardig use of radio frequencies for different types of use. In USA frequencies around 72 MHz is often used. The way of modulating the radio wave to give meaningful information can be AM or FM.
There a several types of actions to be controlled. In a car, there is the actions of the steraing wheels and the actions of the motor. In a helicopter, there are the actions of the motor, the foreward-backward actions of the main rotor, the idewise action of the main rotor, and the actions of the tail rotor, for example. A model can also have extra equipment that must be controlled, foe example video cameras.
The parts or functions in the resceiver and transmittor that is dedicated to each type of action is called a channel. The more channels a RC vehicle has, the more advanced combinations of action can it perform.
The radiotransmission for the different channels must be held apart. This can be done by using slight different frequencies for each channel. If however the control signals are digitally coded, the contol signals can be sent as packages, and in each package there will be infomation about what action types the command regards.
It is important that the controle signal are not blended with signals to controle other vehicles in use. Therefore the person controlling a vehicle must be aware of other transissions going on around the same place, and their frequences. The he must choose another frequency. This can be done in some units by the use of replaceable crystals. More advanced unit use syntisizer tchnology, called Phace Locked Loop, that can modulate the wanted frequency.
Som modern types of controllers use spred spectrum technology. In this thecnology used by the transmittor and resceiver variates in a cyclic manner all the time. Then it is little chance that two vehicles use exact the same frequency at any given time slot.
USA and Canada reserved radio frequencies
European reserved radio frequencies
Australian reserved radio frequencies
New Zealand reserved radio frequencies
Amateur Radio License reserved radio frequencies