The Basic Radio System


There are many modern radio systems from which the beginner can choose. There are several common brands including Futaba, Airtronics, JR, Hitec, and Ace. Each of these offers a wide range of options from a simple 2 - channel to a computer assisted 8 - channel system. The buyer is limited only by his budget. A beginner should discuss his choice of systems with his intended instructor. There are several reasons for doing this, the primary reason being that the student's systems must be compatible with the instructor's system if it will be used as a buddy box. This issue will be covered in more detail later.

All basic radio systems consist of four (4) basic components.

Transmitter - The unit which takes the input from the user through the gimbals or sticks, encodes it, and sends it to the aircraft
Receiver - The unit that receives the signal, decodes it, and routes it to the appropriate servo
Servos - The device that converts the decoded signal to mechanical force to operate a control surface
Batteries - The device that provides power for the other devices to operate

There are specific frequencies assigned by the Federal Communications Commission (FCC) for use with airborne R/C models. A beginner must ensure that the system that he chooses is tuned to one of these frequencies. Most radio system manufacturers place a sticker on the outside of the carton that says, "For airborne use only".

The radio that is chosen must meet the 1991 specifications for narrow band receivers. The actual requirements of these specifications need not be known by the beginner because the systems are required to be 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.

The radio system may transmit and receive on either an AM frequency or an FM frequency. The FM frequencies are less prone to interference than the AM frequencies although those using AM frequencies seldom have problems with interference. Some radio systems use one of two types of internal systems to help to nullify interference. These are called PPM and PCM. Each has its advantage but they are only available in more expensive radio systems and should not concern the beginner.

Regardless of the brand of system, the number of channels, or the price, all transmitters have the same basic components. Transmitters may have additional switches, slides, and displays depending on the functions they perform but the basic components remain the same.

Typical Transmitter

Antenna - The telescoping tube that transmits the signal
Batteries - The device that provides power to the transmitter
Battery Meter - The device used to monitor the strength of the transmitter batteries
Crystal - The device that sets the radio frequency of the transmission
Gimbal (or Stick) - The device that allows the user to input desired control movements into the transmitter
Handle - The device for carrying the transmitter
Power Switch - The switch used to apply battery power to the internal components of the transmitter
Trainer Switch - The switch used to allow an instructor to give control of a model to the student
Trim Lever - Slides used to adjust control surfaces during flight

There are two (2) primary modes of operation, meaning the way the gimbals are set up for operation. Ther are unsettled debates as to which mode is the easiest to use and best for a beginner. The modes of operation have become switched between the United States and most European countries. Mode I is primarily used in Europe while Mode II is used in the United States.

Mode 1

Mode I started in the days of reed actuated proportional systems. The transmitters were uniformly set up in this manner. The thought was that the elevator and rudder or ailerons were the primary controls and each should be operated by an opposite hand for precision control. Later this carried over into the more modern proportional systems since this was the mode used by most modelers.

Mode 2

In later years, the thinking changed to the Mode II configuration. More modelers believed that it was easier to control the primary surfaces effectively with the same hand. Mode II grew in popularity and is used almost exclusively in the USA. A beginner does not have to be concerned about which mode he should select since most manufacturers install the gimbals according the most widely used mode for the nation to which the radio system is being shipped.

There have been discussions over the years involving the number of channels with which a beginner should start. Some people say that only three (3) channels should be used; rudder, elevator, and throttle. The argument here is that it is easier for a beginner to only be concerned with using the rudder to make turns and not be concerned with the ailerons. Others contend that four (4) channels should be used; rudder, ailerons, elevator, and throttle. The contention in this argument is that by not using ailerons, a beginner must go through a second phase of beginner training that being learning how to use ailerons. A four (4) channel system offers better control of the model during takeoffs and landings in cross wind conditions. If a beginner chooses to use only three channels, he can set up the trainer so that the ailerons are not used initially and then add them later. The four (4) channel approach to training is more widely accepted today.

A beginner might consider buying one of the more advanced six (6) channel systems to get some of the features that are not available in the basic system such as dual rate controls. This feature allows the user to reduce the sensitivity of the sticks thereby reducing the chance of over controlling. If the beginner is relatively sure of future goals that involve the use of a six (6) channel system, he can consider this an investment in his future modeling and therefore save money. A lot must be determined before the initial purchase and should be discussed at length with experienced modelers, especially the intended instructor, before the purchase is made.