The radio control (RC) system is the heart of any radio-controlled plane. But, like model kits, there are a vast array of options available. So how do you decide which radio is right for you? Well, let's start with the basics and find out what each part of the radio is, then we'll look at some of the features you might want on your first radio.

What comes with a radio?
A typical R/C aircraft radio set comes with a transmitter, a receiver, several servos, rechargeable battery packs for the transmitter and receiver, a charger (usually this is an "overnight charger" that takes around 10 hours to charge the batteries) and an "on-off" switch for the receiver.

The Transmitter

The transmitter is the link between you and your model. It converts movement on the control sticks into electrical pulses and send them to your model's receiver. Each pulse represents a channel on the model's receiver, and the width of the pulse tells the receiver what the position of the servo should be. The transmitter's frequency is determined by a crystals that plugs into the back of the transmitter. In Australia, there are two frequency bands for R/C models - one for aircraft on 36 Megahertz (MHz), and one for cars and boats on 29 MHz.
The Receiver
The receiver is somewhat similar to the radio you may have in your car, except the receiver in your plane perceives commands from the transmitter and relays them to the servos, while the radio in your car perceives music from a radio station. The frequency of the receiver is again determined by a crystal. The receiver is normally powered by a rechargeable battery pack plugged into the battery slot, but electric models use a different method which is described on the Guide to Electric Power page.
Servos
Servos convert electrical signals from the receiver into the physical movement needed to move the model's control surfaces (such as the rudder or elevator). This movement is in the form of the rotation of a nylon "output" arm or wheel that protrudes from the top of the servo. The output arm pushes or pulls a pushrod that is connected to the control surface. Radio sets usually include several standard-size servos, but mini or micro servos may be more suitable depending on the size of the model.

Radio Options
Now you know how the radio works, we can explain some of the different features and options available, starting with the most important decision - how many control channels you need.

Number of Channels
For each control on your plane, you need one channel on your radio to control it. Basic aircraft radios have four channels (usually for ailerons, elevator, rudder and throttle). Even if you don't use all of the channels on your first model, a radio with at least four channels is often the cheapest option in the long run as you won't need to keep upgrading your radio as you become interested in more advanced models. Also beware that two channel sets are generally only available on radio controlled car frequencies (for which there is no frequency control), so there's an increased chance of your new plane being shot down!

The most common uses for control channels are:

When an electric model does not have a throttle, it flies at full throttle until its batteries cut out. The model is then glided in for a landing.

Frequency
If you're really organised you might like to ask about commonly used frequencies at the club you're a member of or you intend to join. That way you won't have to share your frequency with other flyers, and there's less chance of being shot down by somebody on your frequency!

Servo Reversing
Servo reversing allows you to change the servo's direction of rotation, so that if a channel operates opposite of its intended direction, a simple flick of a switch corrects the problem.

Buddy Box capability
If you're new to radio controlled flying, you might consider buying a radio with buddy box capability. This allows your transmitter to be connected to a compatible transmitter by a cable called a trainer cord. In use, the student only has control over the model when the instructor holds down a button on his transmitter. If the student gets into trouble, the instructor can take over the controls instantly by releasing the button.

Computer Radios
Computer radios provide a set of programmable transmitter features. For example, you could couple two control channels together so that they both move when only one control channel is activated. This has many applications, such as in models which require a combination of aileron and rudder to turn. Computer radios also provide many other very useful features, such as the ability to adjust the centre position and the amount of movement of each control surface from the transmitter.

Which radio?
Now that you understand the basics of radio systems, which radio is right for you? That depends on what you're going to use it for, and of course, your budget. If you just want something simple to get started with and don't need any extra features, then a basic four channel radio is an excellent choice. Or if you're thinking of getting into scale or more advanced models at some stage, a simple computer radio might be a better choice. But like any hobby, you can spend as little or as much as you want!

Introduction | Electric Flight | Thermal Soaring | Slope Soaring Introduction: Welcome | What you'll Need | Your first Model | Radio Systems