Radio/Receivers

Introduction

If the heart of a RC is the motor, the brain would be the radio and receiver. The radio and receiver are the items that everything else in the vehicle need so that they will know how and when to operate. Without it your truck or car is nothing more than just a showpiece sitting on a shelf.

Pistol Grip vs. Stick Radios

There are two types of radios currently being used in RC today. The pistol-grip radio and the stick radio. Most people use the pistol grip radios for cars and trucks, but there are a few people who prefer to use the stick radios with them. The radio system contain two main parts, the radio and the receiver. The radio is what you hold to your hand to control the model. The receiver is a small rectangular or square-shaped box that fits on the model itself. Both pieces will usually have a frequency crystal on them somewhere so that the signals can pass from the radio to the receiver.

Receiver and Servos

The receiver itself can be powered by batteries, or in the case of an electric RC vehicle, it can be powered by the Electronic Speed Control (ESC) provided both the ESC and the receiver have a provision for this that's called a Battery Eliminator Circuit (BEC). The BEC is a common feature, and all but the cheapest components will have it. The BEC allows the standard battery pack that's used to power the car, to also power the receiver. In nitro or other applications where a ESC is not used, a receiver pack will provide the power. The receiver pack can be rechargeable batteries or AA batteries. Depending on the power source used, the voltage may vary some which can affect how fast or slow the servos will operate. To some people this may not matter, but to others it may be very important. It's also the reason that servos specifications have speed and torque details listed at a couple different voltage levels.

There is one other item that may come with your radio receiver kit, the servos. The servo is what turns the signal into an action. The most common purpose would be steering. However a servo can be used for many things, including gear selection and throttle control. In an electric car or truck, an ESC will often take the place of a servo and Mechanical Speed Control (MSC) for handling the motor's operations, but the steering would still be controlled by a servo.

Radio Modulation

The act of transferring information from the radio to the receiver is called Radio Modulation. There are three types of Radio Modulation that radios use to transmit signals to the receiver. They are AM, FM, and PCM.

AM Radios

AM stands for Amplitude Modulation. It sends it signals by varying the amplitude of the signals. AM is the most common form of radio found in RTR kits, and provides a cheap way to control an RC vehicle. You can buy an AM radio/receiver combo starting around the $45.00 range and go up from there. However AM's drawback is it's susceptibility to interference. The signal from an AM radio can be affected by a multitude of things, from overhead power lines to CB radios. Even a large electrical disturbance such as a lightning storm 40 or 50 miles away can affect an AM signal. If you've ever listened to an AM radio station while driving, you've probably noticed how much interference AM is prone to receiving.

FM Radios

FM stands for Frequency Modulation. It sends it signals by varying the frequency of the signals. FM radios are a common upgrade from the cheap AM beginner radios, and the ones found in most RTR kits. FM radio/receiver combos start out around $80 and quickly go up from there. An FM radio is immune from all but the worst interference, and therefore it's commonly used as the equipment for many experienced hobbyists. Spending a little more money on a FM radio/receiver makes a whole lot of sense as you begin to have more money invested in your RC vehicle. After you spend several hundred dollars in upgrades on top of the price of the kit to begin with, do you really want to trust it all to a $50.00 AM radio?

PCM Radios

PCM stands for Pulse Code Modulation. It digitizes the signal as binary code to provide an extremely accurate signal. PCM radios are considered high end units and start around $250 and can easily hit $1500 for the top of the line models. PCM radios are more common among professional racers or those who fly planes. For the hobbyist, an FM radio would probably be the better choice when weighing reliability and cost.

DSM Radios

DSM stands for Digital Spectrum Modulation. This form of data transmission for land-based RC vehicles was thrown into the public spotlight around the beginning of 2005. Data is transmitted in the 2.4GHz range which is well above the frequency range of standard AM and FM units at 27 and 75MHz.

This high of a frequency range has one main benefit. That is the fact that the signal is transmitted well above the frequency ranges that would be affected by common sources of glitching such as the electronics or metal rubbing on the chassis. In the end, this means you get a signal cleaner than anything that our hobby has seen prior to this technology.

Part One:	Introduction
Part Two:	Deciphering the Specifications
Part Three:	Radio Adjustment Tips
Part Four:	Frequency Charts
Part Five:	Recommended Radio/Receiver Combos