The Heart of Radio Control!

The radio control (R/C) system is the heart of our hobby. This magic box can turn a lifeless pile of balsa into a graceful soarer, a flashy acrobat or a snarling 150-mph pylon racer. Which radio is right for you? Read on as we lead you through the maze of features and technical jargon that make up the modern R/C system. Once you understand what all those buttons on the transmitter do, it will be easier for you to decide which radio and features meet your needs.

Control Channels

The first thing you need to decide is how much you want your model to do. For each control function, you need one channel of control. The usual uses for control channels are:
Radio Controls

Control Channel Usage


  • Control Channel*.....Rudder
  • Cars/Boats..............Throttle, steering.
  • Control Channels....Rudder or aileron, elevator, throttle.
  • Control Channels....Rudder, aileron, elevator, throttle.
  • Control Channels....Rudder, aileron, elevator, throttle, flaps or retracts.
  • Control Channels....Rudder, aileron, elevator, throttle, flaps or retracts.
  • * When a powered model does not have a throttle, it flies at full throttle until it runs out of fuel. The model is then glided-in for a landing.
When you have more than 6 control channels, you can add such features as bomb drops, dive brakes, parachute drops, sliding canopies or other operating parts to your model. The most common number of control channels used on a powered aircraft model is 4. Sailplanes, cars, and boats usually use 2-3 channels. Four-channel control gives you full acrobatic capability and will enable you to fly most airplane models.

Mode 1 / Mode 2

Refers to the stick configuration of an aircraft transmitter's control sticks. Mode 1 has the aileron/throttle on the right stick and the rudder/elevator on the left. Mode 1 is popular in Europe and Asia. Mode 2 is the USA standard and has the elevator/aileron on the right stick and the rudder/throttle on the left. Almost all radios used in the USA, Canada, Central and South America are Mode 2. All 4-channel and above aircraft radios sold by Tower Hobbies are Mode 2 unless otherwise noted.

Radio Modulation

AM: Stands for Amplitude Modulation which transmits by a variation in the amplitude of signals, it is subject to interference more than FM.

FM: Stands for Frequency Modulation which transmits signals by variations in frequency, reduces the risk of "glitches" due to signal interference.

PCM: Stands for Pulse Code Modulation uses binary code to digitize the signal, providing the most accurate signal possible.

2.4GHz: Simply by pushing a button, you link the receiver to a single transmitter -- each 2.4GHz FASST transmitter has been assigned a unique ID code at the factory. Once that link is set, the receiver responds only to that one transmitter. In addition, the 2.4GHz systems never stay on a single frequency for more than two milliseconds. You never have to worry about signal conflicts, and never need to wait for an open frequency

Secure Link Technology™ (SLT™)

 To get the most out of your model you need confidence in your radio, and that's where Secure Link Technology (SLT) shines. It's proven reliable, eliminating virtually any possibility of interference. An SLT transmitter encodes its signal, and then sends it using true frequency-hopping technology. Only the companion SLT receiver, linked by the push of a button, can capture the signal, decode its commands and relay them to your model.

Secure Link Technology is the protocol used by Transmitter-Ready™ (Tx-R™) aircraft – today's fastest-growing aircraft category. SLT makes it easy to fly dozens of aircraft with the same radio. That's why SLT transmitters are popular with Receiver-Ready Rx-R™ pilots, too!

Servos

Tower Hobbies ServoA servo contains an electric motor and is the "muscle" that moves the rudder, elevator, or other control surfaces. For each channel of control, you need a servo. Most 4 or more control channel radios come with 2-4 servos. There is a wide variety of servo types depending upon their intended use. If your 4-channel radio only comes with 3 servos and you wish to fly a "full-house" airplane (one that has 4 controllable features) you'll want to purchase one additional servo.

2.4GHz Spread Spectrum Technology

2.4GHz Spread Spectrum Technology is among the most common ways to transmit radio signals. It's the fastest, smoothest, most reliable control possible; that's why it's ideal for R/C use.
One common way that 2.4GHz systems operate is by hopping between frequencies, preventing same-channel interference. Secure Link Technology, or SLT, is among today's most popular 2.4GHz Spread Spectrum protocols. SLT is used in Tactic radio systems, along with select transmitters from Tower Hobbies and Hitec. SLT can also be found in the receivers of all Transmitter-Ready (Tx-R) models, as well as the Tactic AnyLink 2.4GHz Adapter.
SLT systems feature fast, easy push-button linking…a feature that's also found in Futaba protocols. S-FHSS/FHSS, FASST™ and FASSTest are among their most popular. S-FHSS and FHSS are used in Futaba sport systems. FASST systems offer additional measures to improve dependability. The first is Continuous Channel Shifting, which switches broadcast channels several times per second. FAST systems also feature Dual Antenna Diversity, as well as exclusive Pre-Vision, which detects and corrects signal errors before they reach the receiver. FASSTest, the newest Futaba protocol, is the most sophisticated protocol of all – yet it can be used with S-FHSS and FASST electronics!

Fail Safe(FS)

This feature automatically returns a servo or servos to neutral or a preset position in case of a malfunction or interference.

Dual Rates

A dual rate switch on the transmitter can reduce the amount of servo travel. This makes the controls less sensitive. The aileron and elevator control channels are the most common channels with this feature, although some radios will also have a rudder dual rate switch. Select low rate, and an over responsive model can be made easier to control. Since beginners tend to over-control the model, low rate can also tame their models.

NiCd (Nickel-Cadmium) Batteries

The most common and economical type of battery. The voltage of a typical NiCd (or NiMH) cell is 1.2V.

NiMH (Nickel-Metal Hydride) Batteries

While about the same size and weight as NiCd cells, NiMH cells offer a wider range of capacities. NiMHs are also more environmentally friendly, requiring neither cycling or recycling.

LiPo (Lithium-Polymer) Batteries

More costly than NiCd or NiMHs, LiPos also offer higher performance due to lighter weight (about half that of NiCds or NiMHs) and higher voltage (3.7V, or 4.2V for balanced cells.)

LiFe (Lithium-Ferrite Phosphate) Batteries

Lithium-based LiFe cells are flat and thin like LiPos, but offer less volatility and slightly lower voltage.

Trainer System

Some trainer systems – like those found on select Futaba transmitters – connect two separate transmitters by means of a trainer cord. This way, the instructor can pass control over to the student's transmitter so that he can fly. If the student gets into trouble, the instructor can regain control instantly. Wireless trainer systems – like those found on select Tactic transmitters – act the same way, connecting a teacher's transmitter to a student's. The only difference is that a trainer cord isn't necessary, since the wireless connection is built into the transmitter.

Servo Reversing

This feature allows you to reverse servo rotation. If a channel operates opposite of its intended direction, a simple flick of a switch corrects the problem.

Adjustable Travel Volume(End Point Adjustments)

ATV allows you to preset the maximum travel of a servo to either side from its neutral position. Such settings help tailor control action to suit your flying or driving style.

Exponential Rate(Adjustable Rate Control)

This feature smoothes responses between stick or wheel and the controlling servo movement.

Direct Servo Control(DSC)

This feature permits you to check servo operation without broadcasting a radio signal. A cable connects the transmitter to the receiver. Direct servo control is very useful for on-the-ground control checks.

Mixing(Coupling)

Two control channels can be coupled together so that they move together when only one control channel is activated. Many 1/4 scale models require a combination of aileron and rudder to turn. Mixing does this electronically at the transmitter. V-tailed models, where the two halves of the V-tail must move not only together but independently, are another use of control mixing.

Programmable or Computer Radios

These high-tech radios are not inexpensive but allow a full set of programmable transmitter features like multiple plane memory, preprogrammed maneuvers (rolls, loops, etc. at the touch of one button) and much more.

Airplanes/Sailplanes

  We suggest that you get a 4-channel radio with NiCds to start with. Even if you are only flying 2-channel airplanes and sailplanes, NiCd batteries are worth the extra money. Other useful features you’ll want to consider are servo reversing and a trainer system. Select from the other features to suit your future needs. You might not use them to start, but they will be there when you are ready. Be sure to match the radio system to the aircraft you intend to fly. Since there is such a large range of model types, you should select the type of radio to suit your particular tastes. If you’re going to be flying a .40-.60 sized trainer, a basic 4-channel radio with standard servos will be fine. You could easily buy more radio than what you’ll need, but save your money for things like fuel, glue and field equipment.

In a sailplane, space and weight are very important. Choose a radio with smaller size servos for all but the largest of sailplanes. Since most sailplanes use only 2 channels, a 2-channel radio is all that is needed. A sailplane with a 2-channel radio is just about the least expensive way to get into the hobby of R/C flying. If your budget allows, go ahead and get a 4-channel now and just install only two of the servos. This will give you the safety and convenience of rechargeable NiCd batteries as a bonus.

If you’re looking for a high-quality, 4-channel airplane radio, then look no further than Futaba’s own 4YF 2.4GHz FHSS Computer Radio. It has all of the features you’ll need. It's perfect for sailplanes, electrics and park flyers.


What comes with an Air Radio System?

Most Aircraft Radio Systems come with: Transmitter (Tx) - The hand-held radio controller. This is the unit that sends out the commands that you input.

Receiver (Rx) - The radio unit in the airplane which receives the transmitter signal and relays the control to the servos. This is somewhat similar to the radio you may have in your family automobile, except the radio receiver in the airplane perceives commands from the transmitter, while the radio in your car perceives music from the radio station.

Servo - The electromechanical device which moves the control surfaces or throttle of the airplane according to commands from the receiver. The radio device which does the physical work inside the airplane.

Batteries - 2 and 3 channel systems generally do not come with batteries and extra Alkaline "AA" batteries will be required. However most 4 or more channel radio systems will come with NiCd rechargeable battery packs for your receiver and transmitter and will include a charger. Check the requires section of the radio system you have chosen to make sure what is included and what is not.

Even though surface systems are used for boats, motorcycles, cars and trucks, we suggest the same thing for all: a 2-channel radio. And here, you have a choice between stick and pistol (wheel) styles.   Stick radios are square and flat and named for their primary control. In addition to (generally) lower prices, stick fans also note that 2-stick flight systems and 2-stick surface systems require the same skills — a plus if you plan to become a pilot down the road.   Despite those facts, pistol radios are far more popular. The trigger finger on the hand that holds the pistol (usually the left) controls the throttle and brake. The thumb and fingers on the free hand steer the wheel. Fans claim that pistols are easier to hold and less tiring to use. Extras: NiCds, a high-torque steering servo (for larger vehicles); BEC receiver and ESC (for electrics); and steering dual rates, exponential and ABS braking. Here's another: a 3-channel radio, which may allow you to adjust or remote-start an engine, shift gears or control a timer.


Pistol-Grip Radios

The pistol-grip radio with steering wheel offers the unique feeling of real driving control and is the more popular option for cars, trucks and boats. Turning the wheel of the transmitter duplicates the steering techniques of full-size automobiles and boats. The shape of the transmitter is similar to that of a pistol; the wheel is located on the right side of the radio and the throttle is controlled by the left index finger in the trigger position. It's a very comfortable and convenient method of control.

2-Stick Radios

The two-stick radio is easy to use in cars and boats - even though they aren't controlled by a steering wheel. The two-stick radio helps you develop the same automatic reflexes for steering and throttle as with airplane radios. This enables you to make an easier transition if you choose to fly airplanes later on. (With a pistol-grip radio, some relearning will be required.) In addition, the two-stick radio is also the least expensive of the two types of car/boat radios.

Q: Aside from the obvious, what are the differences between an airplane and a heli radio? They look practically identical.

A: Though heli radios look like airplane radios, there are some very basic differences. For instance, most heli-capable radios include special mixing functions to simplify set-up, perform aerobatics and fine-tune performance. But the bigger difference between them is the number of control channels. Some sailplanes require just two; many airplanes can get by with four. Most helis, however, require at least five and sometimes six.

Q: When people talk about radios, I keep hearing all these terms – PCM, 2.4GHz, Spread Spectrum and so on… What do they mean?

A: All of these terms are related to the radio's signal transmission, including how secure and interference-resistant the signal will be over today's crowded airwaves. PCM stands for Pulse Code Modulation. Many high-end radios are PCM-based because they're less likely to have issues with interference. PCM radios are also compatible with a wide range of receivers and include Fail-Safe. 2.4GHz/Spread Spectrum systems shift signals hundreds of times per second, virtually eliminating any chance for interference to occur. 2.4GHz systems are also more convenient, finding frequencies without the use of frequency pins or crystals. Users no longer have to worry if someone else is operating on their frequency. They just have to go to the field, turn on their radio and start flying! If there are more R/C terms you'd like to know about, be sure to check out Tower Hobbies' R/C Dictionary!

2.4GHz – also Spread Spectrum. The newest radio band available for R/C use. Operates at higher frequencies than noise to reduce signal interference. It requires no crystal or channel selection allowing an almost unlimited number of modelers to operate at the same time.

AM (Amplitude Modulation) — AM radios control a model by varying the amplitude (height) of a radio signal. AM radios are the least costly, but the most affected by interference. See also FM (PPM) and PCM.

Analog — A radio that transmits control signals by changing voltage levels. Analog systems tend to cost less, which makes them ideal for beginners. See Digital.

ATL (Adjustable Throttle Limiter) — This actually affects the braking action on a pistol, by limiting how far forward the trigger can move (travel.) May be adjusted mechanically, electronically or (rare) both ways.

ATV (Adjustable Travel Volume) — See EPA.

Band — The wavelength on which a radio transmits, as measured in megahertz (MHz) or gigahertz (GHz). There are currently five legal bands for R/C use: 72MHz (for air use), 75MHz (for surface use) and 27MHz, 50MHz and 2.4GHz, which can be used for either air or surface systems.

BEC (Battery Eliminator Circuitry) — BEC eliminates the need (and weight) of a receiver battery, by allowing the receiver to draw power from the power battery.

Buddy Box — A “dummy” transmitter used in flight training. Once connected via a trainer cord to a master radio, it: 1) allows the student to control the model remotely through the instructor’s radio, and 2) allows an instructor to take control whenever necessary.

Channel (as in a “2-channel radio”) — In general, it takes 1 channel to control one R/C function. A 2-channel radio is a 2-function radio.

Channel (as in “Channel 72”) — Here, “channel” means a specific frequency. Channels are identified by a number or by a letter and number.

Crystal (also Xtal) — Crystals control the radio signal’s frequency. Transmitter and receiver crystals must be on the same frequency. The exception: synthesized radio systems. (See below.)

Digital — A digital R/C system that transmits control input as a computer code and not by voltage levels as analog systems do. Generally, digital systems offer more set-up versatility and data storage (memory).

DMSS (Dual Modulation Spectrum System) — A 2.4GHz protocol developed and use by JR. It uses variations of both DSSS and FHSS for a secure signal.

DSC (Direct Servo Control) — Allows you to link the transmitter and receiver with a cable, and check/adjust servo operation without broadcasting a signal. A high-end convenience.

DSSS (Direct Sequence Spread Spectrum) — A 2.4GHz radio system which selects one (or two) of the available “free” frequencies and transmits only on the one(s) chosen. Like FHSS (Frequency Hopping Spread Spectrum) systems, it is more resistant to electrical “noise” than AM, FM or PCM systems. It reduces the potential for same-channel or adjacent-channel interference by concentrating the transmitter’s signal and “diluting” any competing signal. See also FHSS.

D/R (Dual Rates) — This adjusts control sensitivity, or how far a servo will move with a given input. Low rates reduce it, slowing response — great for taming “skittish” models or helping newcomers avoid overcontrol. High rates speed and strengthen response.

EPA (Endpoint Adjustment. Also known as ATV) — Limits how far a servo arm can travel from the servo’s “center” or neutral position. EPA usually allows separate settings for either side of center. ATV may offer only one setting that affects both sides equally. Often found on throttle; also found on elevator and ailerons.

ESC (Electronic Speed Control) — Controls throttle electronically (through compact circuitry) rather than mechanically, with a heavier servo and linkage. Smoother and less complex, ESCs are available with reverse, brake or both.

Expo(nential) — Servo movement is usually linear, that is, in direct proportion to the input. A given input will always cause the same amount of movement. With exponential, a given input will cause different amounts of movement, depending on the control’s position. For example, a control surface can be set up to move at a lower rate near “center” stick, but at normal rates toward the “ends” of the stick.

Fail-safe — A safety feature. Automatically moves a servo (throttle or other) to a preset position when the signal to the receiver is lost.

FHSS (Frequency Hopping Spread Spectrum) — A 2.4GHz radio system that “hops” from one “free” frequency to another. Since it transmits on a different frequency every few milliseconds, the chances of same-channel or adjacent-channel interference are reduced to virtually zero.

Flight Pack — A package of on-board radio gear. Thrifty modelers buy flight packs that duplicate gear in an existing model, which allows them to use one radio with two (or more) models. Includes a receiver and servo(s), but may also include a NiCd and other items.

FM (Frequency Modulation) — FM radios control models by varying signal frequency. Though higher in price, they are much more interference-resistant.

Frequency Module (also RF Module) — Like a crystal, an RF module plugs into a transmitter and determines its frequency (channel).

GHz (GigaHertz) — A unit of measuring radio waves.

Glitch (also Hit) — A radio problem, most often caused by someone else transmitting on “your” channel (frequency).

Input — Short for control input. Input is using the features of your radio to control your model.

LCD (Liquid Crystal Display) — Frequently used on programmable radios to display menus, show settings, or provide constant data updates.

LED (Light Emitting Diode) — Often used as status lights.

Mode I — A flight radio on which the elevator and rudder are controlled by the left stick and the throttle and aileron are controlled by the right stick.

Mode II - A flight radio on which the throttle & rudder are controlled by the left stick and the aileron and elevator are controlled by the right stick. Most stick radios in the U.S. are Mode 2 radios.

Mode III - A flight radio on which the throttle & rudder are controlled on the right stick and the elevator & aileron are controlled on the left stick.

Mode IV - A flight radio on which the elevator & rudder are controlled on the right stick and the throttle & aileron are controlled on the left stick.

MHz (Megahertz) — A unit of measurement for radio waves.

Mixing — A radio function which allows the user to combine the functions of different channels and control them through a single control.

Modulation - The actual coded signal that’s sent via radio waves.

NiCd (Nickel Cadmium) Battery — An easy, affordable alternative to alkaline batteries. Alkaline cells are cheap, but must be purchased when power runs low. NiCds can be recharged and used hundreds of times. “Full” NiCds means that transmitter and receiver NiCds are included.

PCM (Pulse Code Modulation) — PCM radios digitally encode signals, producing very strong, clear transmissions. Thought more expensive than AM or FM, PCM is far more interference-resistant.

Pistol (-Grip) Radio (also Wheel Radio) — A transmitter that has a pistol grip, a trigger for throttle and brake control and a wheel for steering.

PPM (Pulse Position Modulation) — see FM.

Proportional — A non-proportional control function offers only two choices: on or off, all or none. A proportional function provides a wide range of responses, based on the amount of input provided.

Receiver (also Rx) — An electronic device in the model that converts transmitter signals into electrical impulses for servos.

RF Module — See Frequency Module.

Runaway — A model that’s out of control. Whether it’s due to a glitch or a mechanical problem, it’s a danger to everyone.

Rx — Abbreviation for receiver.

S-BUS — Uses digital serial data communication technology to transmit control signals between your receiver and servos allowing for more servos to be connected to a single receiver.

Servo — The transmitter is the model’s brain. Servos are its muscles. The motor shaft in a servo rotates, which moves a servo arm. The arm is connected by linkages to a function. Control input makes the servo arm move and perform the function. As a rule, each function requires its own servo. Generally, systems include one or more servos. These may be analog or digital, and range in size from tiny Nanos™ to ¼ scale or “monster” types. Speeds, torque and features vary widely, depending on design and application.

Servo Center (also neutral) — The position a servo arm returns to when its control (stick, trigger, switch, etc.) is at its neutral position. (This depends on how a servo arm is installed.) Centering is how quickly and accurately a servo returns to center.

Servo Reversing — Reverses the way a servo rotates with the flip of a switch. A major convenience in servo mounting (installation).

Servo Tray — The place inside a model where servos are mounted (installed). Many also feature cutouts to speed mounting work.

Steering Trim — Adjusts the servo center on the steering channel of a surface radio so a constant input is not needed.

Subtrims — Allow you to adjust a servo's center point. This allows you to re-center the main trims without losing previous adjustments.

Sx — Abbreviation for servo.

Synthesis/Synthesized — A highly sophisticated alternative to crystals. Synthesized transmitters and receivers can be tuned to any channel (frequency) in a given radio band. Radios may include a synthesized transmitter, synthesized receiver or both.

Throttle Curve — A function which allows the user to slow or speed up throttle response in a specific part of the servo’s throw.

Throttle Trim — A function which allows the user to change the idle position/speed of a motor or engine.

Throw — A servo’s total range of travel.

Trainer System — With trainer system, an instructor can link his radio with a student’s radio (or buddy box) through a trainer cord. This allows the student to learn new skills, but also allows the instructor assume control to prevent crashes.

Transmitter (also Tx) — The hand-held part of a radio system. Stick transmitters are primarily for flight, robots and some scale models, while pistol (wheel) radios are common picks for cars, trucks and boats.

Trigger — The throttle and brake control on a pistol radio.

Trims — Adjust servo centering so you don’t have to hold a control input to make the model perform.

Triple Rates — A feature that allows you to create three (response) rates for a specific function or to adjust the “feel” of the model to your style.

Tx — Abbreviation for transmitter.

Xtal — See crystal.

Y-harness — Usually means wire and connectors that have already been assembled in a “Y” shape for a specific use.

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