What Comes With Your Radio System?
Generally you will get just about everything you need
when you purchase your radio system. As an example, most aircraft and helicopter systems
(of four or more channels) come with transmitter, receiver, three or more servos,
rechargeable NiCad batteries for both the transmitter and receiver, battery charger,
switch harness, servo trays, aileron extension, frequency flag and extra servo control
arms. I mention this because these account for the bulk of the systems on the market
today. Next comes the surface radio systems. Some surface radio systems do not
usually come with batteries or charger and only have two servos. For a given radio system, there are usually several different packages
available, each for an intended purpose.
transmitter is the control box which you hold that converts your human control movements
into electrical impulses and sends them via radio waves to the receiver in your model.
receiver is the small electronic unit in your model which converts the radio signal from
your transmitter into electrical control signals which can be sent to your servos.
Servos Servos are
the devices in the model which actually produce the control movements. They convert the
electrical signals from your receiver into physical movement to control your model. A
different servo is required for each control function or radio channel.
Batteries Two and
three channel radio systems, for the most part, do not come with batteries and additional
Alkaline (AA-type) cells are required. Again, these systems are generally used in surface
vehicles. Virtually all 4 channel and greater systems come complete with NiCad
rechargeable battery packs (for both transmitter and receiver) and charger.
Types of Radio Modulation
When shopping for a radio, you will find that people refer to different types of
modulation. They are referring to the way the electronic control information is sent from
your transmitter to the receiver over radio waves. The types being AM,
FM and PCM.
The following is a list of other
functions and features which may be available on various radio systems. Most of
these are for aircraft radios, but I have included them because you may need this
information later. Plus, it's good reading.
This feature allows the modeler to reverse a servo's rotation direction at the flip of a
switch. Servos can be mounted in the most convenient way without concern for their
rotation direction. The proper movement can then be selected when the installation is
Dual Rates (D/R)
Dual Rate allows the modeler to choose between two different control sensitivities. With
the dual rate switch in the "OFF" position, 100% servo throw is available for
maximum control response. In some more sophisticated systems this "OFF" position
may be adjusted to provide anywhere from 30% to 120% of normal full throw. In the
"ON" position, servo throw is reduced and the control response is effectively
desensitized. The amount of throw in the Dual Rate "ON" position is usually
adjustable from 30% to 100% of total servo movement. The modeler can tailor the
sensitivity of his model to his own preferences.
Exponential Rate is where the servo movement is not directly proportional to the amount of
control stick movement. Over the first half of the stick travel, the servo moves less than
the stick. this makes control response milder and smoothes out level flight and normal
flight maneuvers. Over the extreme half of the stick travel, the servo gradually catches
up with the stick throw, achieving 100% servo travel at full stick throw for aerobatics or
Variable Trace Rate (VTR)
This radio function is similar to exponential except it uses two linear responses
to determine the servo sensitivity on the first and second half of the control stick
Fail Safe (FS) An
Electronically programmed mechanism in most PCM radios which automatically returns a servo
or servos to neutral or a preset position in case of radio malfunction or interference.
Adjustable Travel Volume
(ATV) Frequently referred to as End Point Adjustment, ATV lets you
independently preset the maximum travel of a servo either side of neutral.
||Adjustable Function Rate (AFR) Similar to ATV, AFR allows end point
adjustment independent of Dual Rate or Exponential settings.
Sub Trim A radio function which allows very
precise electronic centering of servos.
Direct Servo Controller (DSC)
Allows full function of an aircraft's servos via an umbilical cord. This permits
adjustment of radio functions without switching on the RF portion of a transmitter.
Electronic coupling of one channel to another. This one control input will yield
output to two different servos.
Adds rudder control when aileron is input from the transmitter aileron stick.
V-Tail Mixing Used
when there is a V-Tail on the aircraft rather than the conventional elevator and rudder.
Each control surface of the V is connected to a separate servo. Operating the elevator
control stick will move both surfaces up for back stick or both surfaces down for forward
stick. Moving the rudder control stick left will move the left surface of the V down and
the right surface up. Moving the rudder control stick to the right will move the left
surface of the V up and the right surface down.
Mixes the Flap and Aileron functions so that when each aileron is connected to a separate
servo (one servo plugged into the aileron channel and the other plugged into the flap
channel), the surfaces will act as both ailerons and flaps, depending on the position of
Mixes the Elevator and Aileron functions, especially useful for delta-wing models where
the elevator and ailerons are the same control surfaces. Each surface is connected to a
separate servo (one servo plugged into the aileron channel and the other plugged into the
elevator channel), the surfaces will act as both ailerons and elevator, depending on the
position of the controls.
Couples the Flaps and Elevators such that when the flaps are lowered, the elevator
will be automatically adjusted to prevent pitching of the model.
Couples the Elevators and Flaps such that when control is input to the elevators,
the flaps will move in the opposite direction. This permits the model to perform tighter
maneuvers in the pitch attitude.
Primarily used in gliders for spoiler action by mixing the flaps and ailerons. It is
necessary for the ailerons to be using separate servos, plugged into separate channels and
the flap servo to be independent of both aileron channels. Upon applying Crow Mixing, the
flaps go down while both ailerons go up.
This type of mixing is accomplished by having separate servos on each aileron,
plugging one into the aileron channel and the other into another unused channel. The two
channels can be programmed to both operate from the aileron control stick, however the
travel volume for each aileron may be adjusted separately giving more deflection in one
direction (usually up) than in the other.
Mode I The control
stick configuration with the rudder and elevator being controlled by the left stick while
the right stick controls the throttle and ailerons.
Mode II The
control stick configuration with the ailerons and elevator being controlled by the right
stick while the left stick controls the rudder and throttle.
Mode III The
control stick configuration with the rudder and elevator being controlled by the right
stick while the left stick controls the ailerons and throttle.
Dual Conversion refers to the method in which the receiver processes the incoming signal.
Generally a Dual Conversion receiver is less prone to outside interference and is the
preferred type of receiver.
Trainer System The
trainer system feature allows two transmitters of similar design to be connected together
via a cord (trainer cord) so that one transmitter may be used by an instructor and the
second one by a student when teaching to fly. The instructor simply has to hold a switch
on his transmitter to give the student's transmitter full control. If the student gets
into trouble, the instructor can release the switch and he has full control of the model.
Snap Roll Button
This feature is found on more complex radios and is used to perform a snap roll maneuver
by simply pressing one button. The function is usually programmable to give a combination
of rudder, elevator and aileron control.