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 What is a Radio System? Radio systems normally come with a transmitter (the controller), a receiver, and two servos. Servos go inside the car to control the steering and a mechanical speed control, and are linked to the receiver. Some radio systems are offered with one servo, or one servo and an electronic speed control (ESC). High-end radios are typically sold with just the transmitter and receiver permit the racer to purchase the rest of the system for his needs. Transmitter Basics When buying your first radio system, you'll want to know that the transmitter has the features that are right for your kind of vehicle. The word channel is used two different ways when talking about radio control equipment. First, a car radio is typically a two-channel radio. This means that it controls two functions on the car. The first function is the steering and the second function is throttle (for both forward and reverse travel). Secondly the word "channel" also refers to the actual radio frequency in Megahertz or (MHz) which the radio transmits. There are several frequencies legal to use for RC and each one has been assigned a channel number for simplicity. The same way each TV station transmits on a certain frequency but is referred to by a channel number. Frequencies There are two separate frequency bands, 27MHz and 75MHz. There are thirty-six total channels, or radio frequencies: 27MHz (channels 1 through 6); and 75 MHz (channels 61 through 90). Identical channels (or frequencies) cannot be operated at the same time. In other words, two radios on channel 68, regardless of radio type or signal type, cannot use their radios at the same time. Drivers of nitro powered RCcars prefer 27 MHz since it is more resistant to noise created by engine vibration. However, this band is limited to only six different channels. The 75-band offers 30 channels so it is less likely that someone will be on your channel. It is possible to change your radio's frequency by changing the crystals in the transmitter and receiver. The crystal controls the frequency. Replacement crystals cost anywhere from $12 to $25 according to the brand and signal type. If you race, you really need at least one set of crystals on a different frequency. Be sure to use the correct brand crystals or the performance of your radio will suffer greatly! Transmitter Features The following features can be found on many economically priced radios: Servo Reversing With any given radio installation, control inputs may end up backwards. This may be due to the linkage design of the car or the individual servo's rotation. For example, when you move the transmitter wheel to the right, the car's wheels steer left. To remedy this, transmitters have servo reversing switches. Just flip the switch and everything will move the right way. Steering Dual Rate This function lets you electronically limit the amount of steering your car will have. At the press of a button or the throw of a switch you can have two steering rates--full throw or limited low. Usually the limited throw rate has an adjustment knob or "pot" for fine tune adjustments. Dual rate is important for on-road cars because it helps prevent the rear wheels from sliding out (caused by "over steer," a skittish, hard-to-control condition). Throttle ATV ATV stands for adjustable travel volume. This function limits the amount of servo movement needed for brake and throttle on a nitro-burning car. It eliminates extra stress on the servo. On an electric remote control car you can use it to limit the amount of power from the speed control. This is especially nice when learning how to drive or passing the controls to a less experienced driver. The following features are usually found on more advanced radios: End Point Adjustment EPA allows each direction of movement to have different throw. For example, if your car turns more to the left, turn down the left steering EPA dial until the car turns the same amount in both directions. Turning down the amount of left steering will not change the amount of steering to the right. Sometimes, this feature is called steering "balance." Exponential Sometimes called adjustable rate control, ARC or EXPO. This feature can be used to smooth the car's responses without changing the overall amount of steering or throttle necessary for good control. Some cars need a maximum amount of steering at low speed. However, when that same car is at high speed, steering can become overly sensitive. Exponential changes the relationship between the wheel and the steering servo. One way of viewing exponential throw is to call it soft-center steering. At high speed, you want less steering throw around the neutral or straight-ahead steering position of the wheel. With exponential in use, at full steering wheel throw, full steering is achieved. The same principle applies to throttle trigger and actual throttle response. Steering Sub-Trim This is a handy feature that allows you to quickly and very accurately adjust steering neutral when running your RC car for the first time or any time. It works in addition to, and in the same way as, the regular steering trim knob found on the outside of the transmitter. It's a great way to keep the external trim knob (or tab) in its neutral position for full left and right throw potential. Radio Receivers The receiver is your vehicle's brain. This little "black box" is installed in your car. It receives the transmitter's radio signal with its encoded control inputs right out of thin air, translates and separates the code and sends commands to the servo(s) or speed control. For best reception, receivers must be mounted as far away from battery and motor wires as is practical. Not doing this may cause radio interference. Typically, this is the most common mistake first time racers will make. Never let your receiver get wet! If you have a nitro car which ejects fuel residue (most do), or if you run your gas or electric car where it's a little damp (e.g. wet grass), tuck the receiver inside a big latex rubber balloon or in a protective cover to keep it dry. Servos Servos either make the car steer or make the mechanical speed control move when you move the controls on your transmitter. They come in all sizes, speeds, and strengths. Choosing the right servo depends on the demands of the car and driver. To get the most response for your off-road truck you'll want "monster" torque. For a 1/10th-scale, on-road pan car, you'll want lightning speed. Some drivers find a slower servo helps them corner with smoother control. Damaged servos can be easily repaired with factory replacement parts. So, don't throw them away because for a few dollars, you may be able to make them as good as new. Next tip |
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