Radio Control Systems the Real Basics

ast month I introduced the subject of
learning model aviation “from the
ground up.” As the name implies, this is
a beginner series that will be devoted to
people at the entry point of our
wonderful hobby. The sequence of
articles planned for this series follows a
logical order to allow you to enjoy the
learning process. After all, it is a hobby
and it is supposed to be fun.
Since approximately 90% of modelflying
enthusiasts resort to Radio
Control (RC) systems for flight control,
this was judged the best starting place.
The article has literally been developed
from square one. If you already have
some knowledge of RC devices, you
might consider our presentation too
basic. We will try to describe all aspects
of RC for the benefit of the entry-level
hobbyist.
What Does an RC System Do? The
basic idea is that you—the pilot—stand
on the ground holding a radio
transmitter. The transmitter operates as
any broadcasting-type device, except in
this instance voice is not transmitted; a
coded signal is sent to the model aircraft
up in the air.
Onboard that aircraft is a radio
receiver that receives these coded
signals without the need for
interconnecting wires. The received
signal is decoded or processed then
passed on to individual motor-driven
actuators (servos)
that physically
move the aircraft
control surfaces and
adjust (or change)
the engine speed
settings (known as
throttling). The
radio transmitter
(which the pilot
holds) and the
receiver/servos in
the model are
powered by
batteries. So as a
newcomer, you
must become
familiar with the RC
system and the
batteries that power
it.
The entire thrill
of RC flying is the
ability to control the
model’s attitude in
flight, sometimes at
distances of several
hundred feet away, maneuvering the
airplane and landing it close by, just like
a full-scale aircraft. Judgment,
experience, and skill development enter
the equation when it comes to the model
aircraft’s flight.
The First Thing You Should Do:
Before you purchase anything, you owe
it to yourself to visit a local RC flying
field. A hobby dealer in your area
should be able to steer you in the right
direction. A referral to a local RC club
can also prove helpful. The idea is to get
you and possibly other family members
out to see these models in flight
firsthand.
You may be able to talk with some
Radio Control
L
New Hitec RCD Neon three-channel FM RC is interesting
concept; buy basic system, then buy add-on features as
flying skills improve. Transmitter is in background;
charger is on left; receiver and battery box are in center;
two servos are on right. This system, as a basic offering,
comes with two servos and battery box that can hold
four alkaline-type nonrechargeable batteries.
Hitec Neon three-channel FM airborne components (that go inside model). Receiver is at
top; below is four-cell battery box intended for nonrechargeable alkaline cells; two HS-
81 miniature servos are at right. This type of lightweight RC system is intended for small
glow-powered models (.049-.15) and park-flyer electric-powered models.
Typical RC system—Hitec Laser 6 (sixchannel
function transmitter with four
servos)—as it arrives in Styrofoam
shipping container. Transmitter is at
bottom; four servos are at top. Included
are receiver, battery charger.
54 MODEL AVIATION
04sig2.QXD 1.24.03 8:52 am Page 54
of the experienced fliers and get a rough idea
of what is involved. These same people
should be able to make initial
recommendations concerning types of RC
systems, popular system brand names, model
aircraft suitable for initial flight instructions,
engines to power the airplanes, and the
necessary supporting equipment to get you
started. All of these elements will be
discussed in-depth as this series grows month
by month.
How Are RC Systems Classified? RC
systems in the most basic sense provide
control of the aircraft rudder (for steering left
and right), elevator (for pitch control or up
and down motion), and engine throttle
(control engine speeds from idle up through
full power). Each of these basic flight-control
functions is classified as a channel function
(rudder, elevator, and throttle). Keeping that
in mind, RC systems are classified by the
number of channel functions offered—two,
three, four, and in the cases of the most
advanced systems, upward of eight to 10.
When you go out to shop for your first
new RC system, you will see a few basic
two-channel systems (rudder and elevator);
they are only suitable for flying model gliders
or sailplanes, where engines are not
employed, therefore a throttle is unnecessary.
Since two-channel function control is limited
in application, the initial point of
consideration when buying your first radio is
a three-channel-function RC system.
A three-channel RC system provides basic rudder, elevator, and
engine control (sometimes called throttle). Several manufacturers,
including Futaba and Hitec, make excellent, easy-to-use threechannel
RC systems which are also inexpensive. Since so much can
be done with a three-channel RC system, it will probably never
become obsolete. Many of us who fly sophisticated radio systems
still own and regularly use three-channel systems because they are
easy to operate.
Looking ahead, there are four-channel RC systems which
comprise the most popular category. With four channel functions, the
added control is ailerons, which are located on the wing and permit
the model to bank in flight. By adding aileron control to rudder,
elevator, and engine control, you have essentially the same form of
control as used on full-scale aircraft. As you progress in the RC
hobby, you will sooner or later want to expand your horizons and use
all four basic channel functions.
Your first choice for an RC system should be a three-channelfunction
radio. That will hold your initial investment to a minimum.
If you enjoy the hobby and want to grow with it, it would be best if
your second radio system were what we call a “full four-channel”
system.
RC-System Operating Frequencies: After selecting the number of
channel functions, your next choice is what frequency to operate on.
This discussion is most important because it involves a basic safety
requirement you must always observe as an RC pilot.
Years ago the model-aircraft hobby was granted a series of 50
April 2003 55
Systems ■ Bob Aberle
Pen points to three-channel RC transmitter’s control stick. Side-to-side motion provides
rudder steering control; fore-and-aft motion controls model’s pitch (up and down).
Comparison of RC receiver, servo sizes. Top left: Hitec RCD
eight-channel receiver capable of controlling models up to large
sizes—1⁄4 scale and up. Top right: Typical- or average-size Hitec
HS-422 servo can easily control models with up to 60-size glow
engines. (These are components from Hitec Laser 6 system.)
Bottom left: Hitec Electron 6 receiver weighs slightly more than
1⁄2 ounce! Companion miniature HS-81 servo is at bottom right.
This receiver, servo is ideal for smaller glow-powered models
and small electric park flyers. (These components are from Hitec
Neon three-channel FM RC system.)
The Real
Basics
04sig2.QXD 1.24.03 9:04 am Page 55
specific frequencies for RC use by the
Federal Communications Commission
(FCC). Just as the FCC assigns radio and
television stations, it has assigned our
frequencies which exist in a band that runs
from 72.000 megahertz (MHz) to 73.000
MHz. Each of the 50 FCC-approved
frequencies (such as 72.010 MHz, 72.030
MHz, etc.) has been assigned a “channel
number” for easy identification purposes.
The term “channel number” has nothing
to do with the channel control functions I
just discussed. I mention this because that
point has caused initial confusion for many
beginners.
Each RC channel (number) is
essentially the same as a radio-station
number or call sign. If you purchase an RC
system on channel 11, it will broadcast a
signal on that exact channel (or frequency).
In this regard, channel number and
frequency are one in the same.
When you purchase your radio system,
there will probably be a label on the box
containing the frequency (expressed in
MHz, such as 72.010 MHz) and its
equivalent channel number (in this case
CH11). When you open the box, the RC
transmitter and receiver will probably be
stamped with the operating frequency and
the channel number.
Keeping this in mind, RC receivers on
the same frequency/channel can receive the
same signal. This is important. If you own
an RC system that operates on CH11 and
another modeler shows up at the flying
field with the same channel number, you
can’t operate or fly at the same time.
Attempting to do so will lead to possible
radio interference and could result in one or
both models crashing. This is your first
safety lesson as an RC pilot.
If two modelers show up at the field
using the same channel, each must wait his
or her turn so that only one model is
operated at a time. To simplify the control
of these RC channel numbers, a two-digitnumbered
flag is supplied with every RC
system. That flag must always be
Pen points to the rudder trim lever, which is explained in the text.
Rear of Hitec three-channel transmitter shows two servo-reversing switches. This
system’s third, or throttle, channel function doesn’t have servo-reversing capabilities.
Pen points to third channel lever, on rear
of Hitec three-channel transmitter. Index
finger of left hand moves this lever. It
controls engine speed (throttle control).
This crystal controls RC transmitter operating frequency; it is located at rear of case.
Note reference to channel number (CH38), operating frequency (72.550 MHz).
Photos courtesy the author Graphic Design by Lydia Whitehead
56 MODEL AVIATION
04sig2.QXD 1.23.03 1:23 pm Page 56
April 2003 57
Channel-number flag or placard is attached to lower portion of
transmitter antenna. Flag must always be displayed at flying field
for channel-identification purposes—a primary safety rule!
Pen points to transmitter power switch. This is how you turn
transmitter on, off. Directly above switch are three colored lightemitting-
diode (LED) indicators that tell battery status. If top
green LED is glowing, battery is okay. If middle yellow LED
lights, recharge or charge batteries soon. If red is glowing, do
not fly until you tend to batteries. Sometimes colored indicators
are replaced by meter or LCD (Liquid Crystal Display)-screen
voltage readout on more sophisticated transmitters.
Same information as above is posted on Hitec RC transmitters.
Excellent placard on side of Hitec receiver gives channel
number, operating frequency, and clearly states that it’s not for
surface use, such as cars and boats.
prominently displayed on the transmitter antenna for all to see. More
will be written about flying-field safety procedures, but for now I
want you to know about the basic controls that are usually in effect
throughout our country.
Each RC flying field usually has a display board that contains a
group of numbered clothespins or clips. There will be 50 of these
pins or clips running from CH11 to CH60. The drill is simple; when
you want to turn on your RC transmitter at the field, you must first
go to this channel-control board. If the clip for your channel is on the
board, that means it is not in use. Remove that clip and attach it to
the transmitter antenna. At this point you may turn on the power to
that transmitter for test or flying purposes.
While you are “on the air,” if any other modeler intends to
operate on the same channel number and goes to the board, the
missing clip will alert him or her that that RC channel is in use. That
person must wait until you are finished flying, have turned off your
Hitec three-channel, single-stick transmitter operates on AM
mode (details in text). Grip transmitter case with left hand. Index
finger of left hand operates throttle on top rear of case. Right
hand grips single control stick for steering, elevation control
(rudder, elevator).
04sig2.QXD 1.23.03 1:25 pm Page 57
transmitter, and have returned the channel clip to the control board.
It’s a simple drill, but if followed faithfully it will prevent any chance
of interference or model crashes. There are more detailed subtleties to
these procedures, but I will leave that until later.
FM, PCM, and AM Modes of Transmission: Since we are dealing
with “radio,” you should be familiar with the terms “AM,” or
Amplitude Modulation, and “FM,” or Frequency Modulation, when it
comes to listening to broadcast radio stations. Except for the station
numbers or call signs, you can usually receive both broadcast modes
on the same radio, and for the most part they sound the same. Sure
there are subtle differences, but the bottom line is that they serve the
same purposes.
In the RC hobby we can use AM, FM, and a special form of FM
called “PCM,” or Pulse Code Modulation. The most popular
operating mode today is FM—much like in broadcasting. The
majority of RC systems sold are FM; it has been that way for the last
20 years. FM provides good, reliable control and can be purchased at
reasonable prices. Few RC systems are still offered on AM.
Some sophisticated RC systems are offered on a special PCM
mode. It adds a proprietary digital code on top of the FM signal, such
that it can offer more protection from outside interference. PCM-type
modulation is only found on the more advanced and more costly
systems.
As a beginner, the one important thing you must keep in mind is
that you can’t mix modulation types between a transmitter and
58 MODEL AVIATION
RC systems come with servo-mounting hardware, extra output
arms (a bag for each servo supplied), frequency-flag set
(bottom).
Typical four-channel airborne RC system goes into average- to
larger-size model. Top: Aileron extension cable, switch harness,
four servos. Bottom left: receiver. Bottom right: four-cell Ni-Cd
rechargeable battery pack. Components weigh roughly 12
ounces; will fly 20- to 60-powered and medium to large electricpowered
models.
Hitec RCD Laser 6 is full four-channel RC system—a step ahead
of basic or beginner’s radio. Transmitter has six-channel
capability; receiver has at least six channel functions. System
comes with four servos to cover four basic flight-control
functions. It costs less than $200 and will serve well for many
years as you progress from beginner through expert!
Standard RC-system dual-output battery charger. Wall-plug
transformer goes in 115VAC outlet. Output cable at left plugs into
transmitter charging jack; cable on right goes to charging jack or
connector on model.
04sig2.QXD 1.23.03 1:26 pm Page 58
April 2003 61
receiver. An FM transmitter will only
operate an FM receiver, and only if both are
on the same frequency (or channel number).
You will never be able to have an FM
transmitter operate an AM receiver or vice
versa.
Taking this a step further, PCM RC
systems must be of the same type and
manufacturer. Each manufacturer employs
different digital codes. Even within a
manufacturing company, several codes
relating to control resolution might be
indicated (such as the expression 512 PCM
and 1024 PCM). For now let’s concentrate
on regular FM, which is in the majority.
Remainder of RC System Components: So
far we have discussed only the RC
transmitter. When you purchase a full RC
system, included in the box will be what we
call the “airborne components” (the
equipment that must go in your model) and
supporting equipment necessary to make the
system operate.
Airborne RC equipment includes the
receiver, a set of servos (usually one for each
channel control function), a battery pack, a
switch harness—usually with a charging
jack—and an aileron extension cable.
A four-channel-function RC system will
usually be supplied with four servos. On
some economy-priced systems, you might
see a four-channel transmitter with only
three servos supplied. This would allow you
to start with three channel functions at a
slightly lower price, then you could purchase
that fourth servo later. I mention this
marketing technique so you are not surprised
when you open your first system box.
The aileron extension cable is supplied
because in most cases the aileron servo is
mounted in the wing structure. The receiver,
located in the model’s fuselage, may be
farther away than the regular servo cable
length. The extension cable comes in handy
for this application. Almost all RC systems
include servo-mounting hardware and extra
output arms (for different applications).
In addition to the airborne components,
you will receive an all-important dual-output
battery charger. Some basic, inexpensive RC
systems are supplied for use with alkaline,
nonrechargeable batteries. Although these
systems work well, this can cost more
money in the long run. For that reason, most
RC systems are supplied with nickelcadmium
(or Nickel Metal Hydride)
rechargeable batteries.
Generally, eight cells are installed inside
the transmitter and four more are used inside
the model. Systems that include rechargeable
batteries also provide the necessary charger.
Most chargers are wall-plug devices. You
plug the transformer (black box) into a
115VAC electric outlet. Two cables exit the
charger; one goes to the transmitter and the
other goes to a charging jack, which you
may be able to locate externally on the side
of the aircraft fuselage. Leaving this charger
plugged in overnight will completely charge
both battery packs.
The other RC-system supporting items
include the frequency or channel-number
identification flag (already discussed) and
hopefully a well-written (most are) operating
instruction manual.
Sizing RC-System Components to the
Expected Size of Your Model: Another
choice when buying an RC system is the size
of the airborne components. In RC we can
have Giant Scale models that weigh upward
of 20-40 pounds and we can have what we
classify as “park flyers”: models weighing
roughly 6-10 ounces. The larger models can
employ larger and heavier receivers, servos
with strong outputs to move the large control
surfaces, and battery packs of high capacity
that can cope with the required extra power.
Large RC components such as this might
weigh 20 ounces or more; that would be
twice the weight of an entire park flyer. The
size of the airborne RC components must be
geared toward your specific model
requirements. The average RC system
generally includes airborne components that
weigh approximately 10-12 ounces which
are capable of flying average models ranging
from 20-size engine power upward of 60-
size engine power.
If you are interested in starting with parkflyer-
size models, your hobby dealer or
04sig2.QXD 1.23.03 1:26 pm Page 61
distributor should be able to steer you to
substantially lighter-weight equipment for
that application. The purpose of this
discussion is to make sure you don’t
accidentally end up the first time with a 20-
ounce airborne radio that is intended to fly
a 10-ounce total-weight park flyer.
Dual-Stick Transmitter Control:
Throughout the years the popular means of
imparting control-signal commands from
the RC transmitter has been through
“control stick assemblies.” These control
sticks provide two-axis type control; we can
obtain two discrete controls from one stick.
If you grip the stick with the fingers of one
hand and rock it side to side, you can obtain
left or right rudder or possibly left or right
aileron control on the model end. Moving
the stick fore and aft at the same time will
prompt elevator or pitch control, making
the model move up or down.
If you purchase a three-channel RC
system, the transmitter will have a single
two-axis control-stick assembly. This will
provide rudder or aileron control along with
elevator control. A small lever on the front,
side, or rear of the transmitter case will
allow you to operate engine throttle on the
model.
A four-channel RC transmitter will have
two two-axis control-stick assembles. With
this popular configuration you grasp the
transmitter case with both hands such that
each thumb rests on the top of a stick. Each
stick will move in two directions. As you
will soon learn, moving a control stick to a
corner will impart a certain amount of
control to two channels at the same time.
The control will be in proportion to the
amount you displace or move the control
stick. That is why it has always been
referred to as dual, simultaneous
proportional control.
The four-channel transmitter usually has
what we call a Mode II control-stick
configuration. It is safe to say that 99% of
all RC-system transmitters sold are with
that configuration. With respect to the two
control-stick assemblies, the right-side
assembly controls aileron (left or right) and
elevator (up and down). The left-side stick
assembly controls rudder (left and right)
and engine throttle (up and down, or
actually low throttle at the bottom and full
throttle at the top position).
The throttle stick does not have a spring
return to the neutral position, as do the
other three-channel functions. Instead it has
a soft detent effect that makes a clicking
sound as you slowly advance or retard the
throttle. When you take your finger off the
throttle stick, it will stay where you left it.
If you bought a full four-channel RC
transmitter at the start, you could initially
use it to control only three airborne control
functions. In that case the right stick
assembly would operate the rudder and
elevator, and the left stick would only
control the throttle. The fourth channel
function would be ignored.
At your local hobby shop or in RCsystem
catalogs, you may see that certain
transmitters do not have control sticks; they
have steering wheels. These radios have
been designed expressly to control surface
vehicles such as RC cars and boats. Per
FCC regulations, they do not operate on the
50 channels (CH11 to CH60) which have
been set aside for model aircraft. These
surface vehicles operate on channels 61
through 75, along with some other channels
in another band.
You should never use one of these
steering-wheel RC transmitters to operate a
model aircraft. Likewise, you should never
attempt to use a dual-stick transmitter,
operating on CH11 to CH60, to control a
surface vehicle. This is a federal law!
Trim Levers: One of the basic controls
you must learn early on involves the use of
trim levers. There is usually one for each
channel number. These trim levers are
located close to the transmitter control
sticks. They usually follow the same path as
the control stick. On the right stick
assembly below the stick there will be a
small protruding lever that moves left or
right, duplicating the same motion as the
rudder-control stick. This lever will be tied
to the left-to-right steering action which
62 MODEL AVIATION
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The IMAA is an international organization was formed April 10,
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of LARGE radio controlled model aircraft throughout the world.
We are the largest Academy of Model Aeronautics (AMA) Special
Interest Group and as such, are committed to representing the
interest of our members in AMA related matters.
Members enjoy the privilege of
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Don’t wait. Join today! For complete
membership details, visit our web site
(www.fly-imaa.org) or give us a call
toll free at – 866 366-4622.
High-Flight,
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all members. High-Flight is
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the activities of IMAA Chapters
and individuals around the world.
04sig2.QXD 1.23.03 1:26 pm Page 62
April 2003 63
might be rudder or aileron, depending on
your application.
When you move this lever, the neutral
position of the rudder control surface
shifts slightly. Full excursion of a trim
lever generally imparts a total of 15% of
the normal control throw. The idea of
using trim is to be able to “zero out” your
aircraft’s attitude in flight so that it will
track straight and level with your hands off
the control stick. Full-scale aircraft have
the same type of trim control.
Most beginner and basic sport-type RC
transmitters use a basic mechanical-type
trim function. The levers have a light
detent action that helps hold the last trim
position. The lever’s position can usually
give you an idea of how much trim is
being employed and to which side (left or
right, up or down, etc.). Some newer RC
transmitters employ a digital-type trim
function. You probably won’t see this on a
basic system, so I’ll leave that discussion
for another chapter.
Servo-reversing switches are another basic
control feature. In subsequent installments
you will read about many extra control
features. Some are even available on basic
radio systems, but we want to give you this
information gradually so you can absorb
everything.
Servo reversing can be found on almost
any RC transmitter, and it can be a real
convenience. Somewhere on your
transmitter case—in the lower front
(exposed or under a flip cover), at the rear,
or even under the battery pack—you will
find a series of tiny switches—one for each
channel function. Flipping one of these
switches will reverse the direction of a servo
located inside your model.
Why is this important? When you make
that initial control installation in your
model, the first time you power up the
system you might find that your left rudder
is actually going right and vice versa. If
you have servo-reversing switches, you
can flip the switch for the channel
involved and the servo will switch
directions. Then when you apply left
rudder at the control stick, the rudder will
move for left control on the aircraft. There
will be more about this later.
That concludes this installment. As basic
as all this may sound, I’m sure you will
have many good questions. We learn from
asking questions and getting the right
answers. This sort of thing is done on
Web-site chat groups; that kind of service
may be offered eventually. In the
meantime, write your specific questions to
“From the Ground Up” in care of Bob
Hunt, Box 68, Stockertown PA 18083; Email:
[email protected].
Along with the monthly articles in this
series I hope to publish product reviews
covering items that would especially be of
interest to the RC beginner. This would
include such things as basic RC systems,
ARF (Almost Ready-to-Fly) training
models, basic model engines, personalcomputer
simulators, training programs,
field-support equipment, etc.
As this series progresses, Model Aviation
hopes to publish articles about constructing
models from kits. Later it expects to go
further and publish construction articles for
simple aircraft trainer designs so the
beginner can get the thrill and experience of
building a model from raw materials (like
from scratch!).
The photos accompanying this article
were taken with equipment in my
possession. The fact that a particular brand
is not shown should not be construed as a
“rating” on my part. At the end I have listed
all the RC manufacturers, their addresses,
and their Web sites when available. All the
RC systems work well and are easily on par
with one another. Your purchasing
decisions will likely be predicated on your
personal requirements rather than the brand
name.
Next month I will get into RC-system
installations, system operation, and briefly
discuss some of the more advanced systems.
I also expect to cover purchasing
aftermarket-type RC components to be able
to operate more than one aircraft from one
transmitter. MA
Bob Aberle
Sources:
Airtronics Inc.
1185 Stanford Ct.
Anaheim CA 92805
(714) 978-1895
[email protected]
www.airtronics.net
FMA Direct
5716A Industry Ln.
Fredrick MD 21704
Sales: (800) 343-2934
Tech/service: (301) 668-7615
Fax: (301) 668-7619
[email protected]
www.fmadirect.com
Futaba Corporation of America:
Distributed exclusively in the US, Canada,
and Mexico by Great Planes Model
Distributors
Box 9021
Champaign IL 61826
www.futaba-rc.com/index.html
GWS:
Balsa Products
122 Jansen Ave.
Iselin NJ 08830
(732) 634-6131
balsapr.com
Hitec RCD
12115 Paine St.
Poway CA 92064
(858) 748-6948
www.hitecrcd.com
JR Remote Control/Horizon Hobby Inc.
4105 Fieldstone Rd.
Champaign IL 61822
(217) 355-9511
Maxx Products International, Inc.
815 Oakwood Rd. Unit D
Lake Zurich IL 60047
(847) 438-2233
Ordering only—toll free: (800) 416-MAXX
(6299)
Fax: (847) 438-2898
www.maxxprod.com/
Multiplex USA—now Royal Hobby
Distributors
8295 Tujunga Ave.
Sun Valley CA 91352
(818) 771-1003
www.multiplexrc.com
Polk’s Hobbies/LMP, Inc.
698 S. 21st St.
Irvington NJ 07111
(973) 351-9800
Fax: (973) 351-9700
www.polkshobby.com
Tower Hobbies
Box 9078
Champaign IL 61826
(800) 637-6050
www.towerhobbies.com
04sig2.QXD 1.23.03 1:26 pm Page 63

ast month I introduced the subject of
learning model aviation “from the
ground up.” As the name implies, this is
a beginner series that will be devoted to
people at the entry point of our
wonderful hobby. The sequence of
articles planned for this series follows a
logical order to allow you to enjoy the
learning process. After all, it is a hobby
and it is supposed to be fun.
Since approximately 90% of modelflying
enthusiasts resort to Radio
Control (RC) systems for flight control,
this was judged the best starting place.
The article has literally been developed
from square one. If you already have
some knowledge of RC devices, you
might consider our presentation too
basic. We will try to describe all aspects
of RC for the benefit of the entry-level
hobbyist.
What Does an RC System Do? The
basic idea is that you—the pilot—stand
on the ground holding a radio
transmitter. The transmitter operates as
any broadcasting-type device, except in
this instance voice is not transmitted; a
coded signal is sent to the model aircraft
up in the air.
Onboard that aircraft is a radio
receiver that receives these coded
signals without the need for
interconnecting wires. The received
signal is decoded or processed then
passed on to individual motor-driven
actuators (servos)
that physically
move the aircraft
control surfaces and
adjust (or change)
the engine speed
settings (known as
throttling). The
radio transmitter
(which the pilot
holds) and the
receiver/servos in
the model are
powered by
batteries. So as a
newcomer, you
must become
familiar with the RC
system and the
batteries that power
it.
The entire thrill
of RC flying is the
ability to control the
model’s attitude in
flight, sometimes at
distances of several
hundred feet away, maneuvering the
airplane and landing it close by, just like
a full-scale aircraft. Judgment,
experience, and skill development enter
the equation when it comes to the model
aircraft’s flight.
The First Thing You Should Do:
Before you purchase anything, you owe
it to yourself to visit a local RC flying
field. A hobby dealer in your area
should be able to steer you in the right
direction. A referral to a local RC club
can also prove helpful. The idea is to get
you and possibly other family members
out to see these models in flight
firsthand.
You may be able to talk with some
Radio Control
L
New Hitec RCD Neon three-channel FM RC is interesting
concept; buy basic system, then buy add-on features as
flying skills improve. Transmitter is in background;
charger is on left; receiver and battery box are in center;
two servos are on right. This system, as a basic offering,
comes with two servos and battery box that can hold
four alkaline-type nonrechargeable batteries.
Hitec Neon three-channel FM airborne components (that go inside model). Receiver is at
top; below is four-cell battery box intended for nonrechargeable alkaline cells; two HS-
81 miniature servos are at right. This type of lightweight RC system is intended for small
glow-powered models (.049-.15) and park-flyer electric-powered models.
Typical RC system—Hitec Laser 6 (sixchannel
function transmitter with four
servos)—as it arrives in Styrofoam
shipping container. Transmitter is at
bottom; four servos are at top. Included
are receiver, battery charger.
54 MODEL AVIATION
04sig2.QXD 1.24.03 8:52 am Page 54
of the experienced fliers and get a rough idea
of what is involved. These same people
should be able to make initial
recommendations concerning types of RC
systems, popular system brand names, model
aircraft suitable for initial flight instructions,
engines to power the airplanes, and the
necessary supporting equipment to get you
started. All of these elements will be
discussed in-depth as this series grows month
by month.
How Are RC Systems Classified? RC
systems in the most basic sense provide
control of the aircraft rudder (for steering left
and right), elevator (for pitch control or up
and down motion), and engine throttle
(control engine speeds from idle up through
full power). Each of these basic flight-control
functions is classified as a channel function
(rudder, elevator, and throttle). Keeping that
in mind, RC systems are classified by the
number of channel functions offered—two,
three, four, and in the cases of the most
advanced systems, upward of eight to 10.
When you go out to shop for your first
new RC system, you will see a few basic
two-channel systems (rudder and elevator);
they are only suitable for flying model gliders
or sailplanes, where engines are not
employed, therefore a throttle is unnecessary.
Since two-channel function control is limited
in application, the initial point of
consideration when buying your first radio is
a three-channel-function RC system.
A three-channel RC system provides basic rudder, elevator, and
engine control (sometimes called throttle). Several manufacturers,
including Futaba and Hitec, make excellent, easy-to-use threechannel
RC systems which are also inexpensive. Since so much can
be done with a three-channel RC system, it will probably never
become obsolete. Many of us who fly sophisticated radio systems
still own and regularly use three-channel systems because they are
easy to operate.
Looking ahead, there are four-channel RC systems which
comprise the most popular category. With four channel functions, the
added control is ailerons, which are located on the wing and permit
the model to bank in flight. By adding aileron control to rudder,
elevator, and engine control, you have essentially the same form of
control as used on full-scale aircraft. As you progress in the RC
hobby, you will sooner or later want to expand your horizons and use
all four basic channel functions.
Your first choice for an RC system should be a three-channelfunction
radio. That will hold your initial investment to a minimum.
If you enjoy the hobby and want to grow with it, it would be best if
your second radio system were what we call a “full four-channel”
system.
RC-System Operating Frequencies: After selecting the number of
channel functions, your next choice is what frequency to operate on.
This discussion is most important because it involves a basic safety
requirement you must always observe as an RC pilot.
Years ago the model-aircraft hobby was granted a series of 50
April 2003 55
Systems ■ Bob Aberle
Pen points to three-channel RC transmitter’s control stick. Side-to-side motion provides
rudder steering control; fore-and-aft motion controls model’s pitch (up and down).
Comparison of RC receiver, servo sizes. Top left: Hitec RCD
eight-channel receiver capable of controlling models up to large
sizes—1⁄4 scale and up. Top right: Typical- or average-size Hitec
HS-422 servo can easily control models with up to 60-size glow
engines. (These are components from Hitec Laser 6 system.)
Bottom left: Hitec Electron 6 receiver weighs slightly more than
1⁄2 ounce! Companion miniature HS-81 servo is at bottom right.
This receiver, servo is ideal for smaller glow-powered models
and small electric park flyers. (These components are from Hitec
Neon three-channel FM RC system.)
The Real
Basics
04sig2.QXD 1.24.03 9:04 am Page 55
specific frequencies for RC use by the
Federal Communications Commission
(FCC). Just as the FCC assigns radio and
television stations, it has assigned our
frequencies which exist in a band that runs
from 72.000 megahertz (MHz) to 73.000
MHz. Each of the 50 FCC-approved
frequencies (such as 72.010 MHz, 72.030
MHz, etc.) has been assigned a “channel
number” for easy identification purposes.
The term “channel number” has nothing
to do with the channel control functions I
just discussed. I mention this because that
point has caused initial confusion for many
beginners.
Each RC channel (number) is
essentially the same as a radio-station
number or call sign. If you purchase an RC
system on channel 11, it will broadcast a
signal on that exact channel (or frequency).
In this regard, channel number and
frequency are one in the same.
When you purchase your radio system,
there will probably be a label on the box
containing the frequency (expressed in
MHz, such as 72.010 MHz) and its
equivalent channel number (in this case
CH11). When you open the box, the RC
transmitter and receiver will probably be
stamped with the operating frequency and
the channel number.
Keeping this in mind, RC receivers on
the same frequency/channel can receive the
same signal. This is important. If you own
an RC system that operates on CH11 and
another modeler shows up at the flying
field with the same channel number, you
can’t operate or fly at the same time.
Attempting to do so will lead to possible
radio interference and could result in one or
both models crashing. This is your first
safety lesson as an RC pilot.
If two modelers show up at the field
using the same channel, each must wait his
or her turn so that only one model is
operated at a time. To simplify the control
of these RC channel numbers, a two-digitnumbered
flag is supplied with every RC
system. That flag must always be
Pen points to the rudder trim lever, which is explained in the text.
Rear of Hitec three-channel transmitter shows two servo-reversing switches. This
system’s third, or throttle, channel function doesn’t have servo-reversing capabilities.
Pen points to third channel lever, on rear
of Hitec three-channel transmitter. Index
finger of left hand moves this lever. It
controls engine speed (throttle control).
This crystal controls RC transmitter operating frequency; it is located at rear of case.
Note reference to channel number (CH38), operating frequency (72.550 MHz).
Photos courtesy the author Graphic Design by Lydia Whitehead
56 MODEL AVIATION
04sig2.QXD 1.23.03 1:23 pm Page 56
April 2003 57
Channel-number flag or placard is attached to lower portion of
transmitter antenna. Flag must always be displayed at flying field
for channel-identification purposes—a primary safety rule!
Pen points to transmitter power switch. This is how you turn
transmitter on, off. Directly above switch are three colored lightemitting-
diode (LED) indicators that tell battery status. If top
green LED is glowing, battery is okay. If middle yellow LED
lights, recharge or charge batteries soon. If red is glowing, do
not fly until you tend to batteries. Sometimes colored indicators
are replaced by meter or LCD (Liquid Crystal Display)-screen
voltage readout on more sophisticated transmitters.
Same information as above is posted on Hitec RC transmitters.
Excellent placard on side of Hitec receiver gives channel
number, operating frequency, and clearly states that it’s not for
surface use, such as cars and boats.
prominently displayed on the transmitter antenna for all to see. More
will be written about flying-field safety procedures, but for now I
want you to know about the basic controls that are usually in effect
throughout our country.
Each RC flying field usually has a display board that contains a
group of numbered clothespins or clips. There will be 50 of these
pins or clips running from CH11 to CH60. The drill is simple; when
you want to turn on your RC transmitter at the field, you must first
go to this channel-control board. If the clip for your channel is on the
board, that means it is not in use. Remove that clip and attach it to
the transmitter antenna. At this point you may turn on the power to
that transmitter for test or flying purposes.
While you are “on the air,” if any other modeler intends to
operate on the same channel number and goes to the board, the
missing clip will alert him or her that that RC channel is in use. That
person must wait until you are finished flying, have turned off your
Hitec three-channel, single-stick transmitter operates on AM
mode (details in text). Grip transmitter case with left hand. Index
finger of left hand operates throttle on top rear of case. Right
hand grips single control stick for steering, elevation control
(rudder, elevator).
04sig2.QXD 1.23.03 1:25 pm Page 57
transmitter, and have returned the channel clip to the control board.
It’s a simple drill, but if followed faithfully it will prevent any chance
of interference or model crashes. There are more detailed subtleties to
these procedures, but I will leave that until later.
FM, PCM, and AM Modes of Transmission: Since we are dealing
with “radio,” you should be familiar with the terms “AM,” or
Amplitude Modulation, and “FM,” or Frequency Modulation, when it
comes to listening to broadcast radio stations. Except for the station
numbers or call signs, you can usually receive both broadcast modes
on the same radio, and for the most part they sound the same. Sure
there are subtle differences, but the bottom line is that they serve the
same purposes.
In the RC hobby we can use AM, FM, and a special form of FM
called “PCM,” or Pulse Code Modulation. The most popular
operating mode today is FM—much like in broadcasting. The
majority of RC systems sold are FM; it has been that way for the last
20 years. FM provides good, reliable control and can be purchased at
reasonable prices. Few RC systems are still offered on AM.
Some sophisticated RC systems are offered on a special PCM
mode. It adds a proprietary digital code on top of the FM signal, such
that it can offer more protection from outside interference. PCM-type
modulation is only found on the more advanced and more costly
systems.
As a beginner, the one important thing you must keep in mind is
that you can’t mix modulation types between a transmitter and
58 MODEL AVIATION
RC systems come with servo-mounting hardware, extra output
arms (a bag for each servo supplied), frequency-flag set
(bottom).
Typical four-channel airborne RC system goes into average- to
larger-size model. Top: Aileron extension cable, switch harness,
four servos. Bottom left: receiver. Bottom right: four-cell Ni-Cd
rechargeable battery pack. Components weigh roughly 12
ounces; will fly 20- to 60-powered and medium to large electricpowered
models.
Hitec RCD Laser 6 is full four-channel RC system—a step ahead
of basic or beginner’s radio. Transmitter has six-channel
capability; receiver has at least six channel functions. System
comes with four servos to cover four basic flight-control
functions. It costs less than $200 and will serve well for many
years as you progress from beginner through expert!
Standard RC-system dual-output battery charger. Wall-plug
transformer goes in 115VAC outlet. Output cable at left plugs into
transmitter charging jack; cable on right goes to charging jack or
connector on model.
04sig2.QXD 1.23.03 1:26 pm Page 58
April 2003 61
receiver. An FM transmitter will only
operate an FM receiver, and only if both are
on the same frequency (or channel number).
You will never be able to have an FM
transmitter operate an AM receiver or vice
versa.
Taking this a step further, PCM RC
systems must be of the same type and
manufacturer. Each manufacturer employs
different digital codes. Even within a
manufacturing company, several codes
relating to control resolution might be
indicated (such as the expression 512 PCM
and 1024 PCM). For now let’s concentrate
on regular FM, which is in the majority.
Remainder of RC System Components: So
far we have discussed only the RC
transmitter. When you purchase a full RC
system, included in the box will be what we
call the “airborne components” (the
equipment that must go in your model) and
supporting equipment necessary to make the
system operate.
Airborne RC equipment includes the
receiver, a set of servos (usually one for each
channel control function), a battery pack, a
switch harness—usually with a charging
jack—and an aileron extension cable.
A four-channel-function RC system will
usually be supplied with four servos. On
some economy-priced systems, you might
see a four-channel transmitter with only
three servos supplied. This would allow you
to start with three channel functions at a
slightly lower price, then you could purchase
that fourth servo later. I mention this
marketing technique so you are not surprised
when you open your first system box.
The aileron extension cable is supplied
because in most cases the aileron servo is
mounted in the wing structure. The receiver,
located in the model’s fuselage, may be
farther away than the regular servo cable
length. The extension cable comes in handy
for this application. Almost all RC systems
include servo-mounting hardware and extra
output arms (for different applications).
In addition to the airborne components,
you will receive an all-important dual-output
battery charger. Some basic, inexpensive RC
systems are supplied for use with alkaline,
nonrechargeable batteries. Although these
systems work well, this can cost more
money in the long run. For that reason, most
RC systems are supplied with nickelcadmium
(or Nickel Metal Hydride)
rechargeable batteries.
Generally, eight cells are installed inside
the transmitter and four more are used inside
the model. Systems that include rechargeable
batteries also provide the necessary charger.
Most chargers are wall-plug devices. You
plug the transformer (black box) into a
115VAC electric outlet. Two cables exit the
charger; one goes to the transmitter and the
other goes to a charging jack, which you
may be able to locate externally on the side
of the aircraft fuselage. Leaving this charger
plugged in overnight will completely charge
both battery packs.
The other RC-system supporting items
include the frequency or channel-number
identification flag (already discussed) and
hopefully a well-written (most are) operating
instruction manual.
Sizing RC-System Components to the
Expected Size of Your Model: Another
choice when buying an RC system is the size
of the airborne components. In RC we can
have Giant Scale models that weigh upward
of 20-40 pounds and we can have what we
classify as “park flyers”: models weighing
roughly 6-10 ounces. The larger models can
employ larger and heavier receivers, servos
with strong outputs to move the large control
surfaces, and battery packs of high capacity
that can cope with the required extra power.
Large RC components such as this might
weigh 20 ounces or more; that would be
twice the weight of an entire park flyer. The
size of the airborne RC components must be
geared toward your specific model
requirements. The average RC system
generally includes airborne components that
weigh approximately 10-12 ounces which
are capable of flying average models ranging
from 20-size engine power upward of 60-
size engine power.
If you are interested in starting with parkflyer-
size models, your hobby dealer or
04sig2.QXD 1.23.03 1:26 pm Page 61
distributor should be able to steer you to
substantially lighter-weight equipment for
that application. The purpose of this
discussion is to make sure you don’t
accidentally end up the first time with a 20-
ounce airborne radio that is intended to fly
a 10-ounce total-weight park flyer.
Dual-Stick Transmitter Control:
Throughout the years the popular means of
imparting control-signal commands from
the RC transmitter has been through
“control stick assemblies.” These control
sticks provide two-axis type control; we can
obtain two discrete controls from one stick.
If you grip the stick with the fingers of one
hand and rock it side to side, you can obtain
left or right rudder or possibly left or right
aileron control on the model end. Moving
the stick fore and aft at the same time will
prompt elevator or pitch control, making
the model move up or down.
If you purchase a three-channel RC
system, the transmitter will have a single
two-axis control-stick assembly. This will
provide rudder or aileron control along with
elevator control. A small lever on the front,
side, or rear of the transmitter case will
allow you to operate engine throttle on the
model.
A four-channel RC transmitter will have
two two-axis control-stick assembles. With
this popular configuration you grasp the
transmitter case with both hands such that
each thumb rests on the top of a stick. Each
stick will move in two directions. As you
will soon learn, moving a control stick to a
corner will impart a certain amount of
control to two channels at the same time.
The control will be in proportion to the
amount you displace or move the control
stick. That is why it has always been
referred to as dual, simultaneous
proportional control.
The four-channel transmitter usually has
what we call a Mode II control-stick
configuration. It is safe to say that 99% of
all RC-system transmitters sold are with
that configuration. With respect to the two
control-stick assemblies, the right-side
assembly controls aileron (left or right) and
elevator (up and down). The left-side stick
assembly controls rudder (left and right)
and engine throttle (up and down, or
actually low throttle at the bottom and full
throttle at the top position).
The throttle stick does not have a spring
return to the neutral position, as do the
other three-channel functions. Instead it has
a soft detent effect that makes a clicking
sound as you slowly advance or retard the
throttle. When you take your finger off the
throttle stick, it will stay where you left it.
If you bought a full four-channel RC
transmitter at the start, you could initially
use it to control only three airborne control
functions. In that case the right stick
assembly would operate the rudder and
elevator, and the left stick would only
control the throttle. The fourth channel
function would be ignored.
At your local hobby shop or in RCsystem
catalogs, you may see that certain
transmitters do not have control sticks; they
have steering wheels. These radios have
been designed expressly to control surface
vehicles such as RC cars and boats. Per
FCC regulations, they do not operate on the
50 channels (CH11 to CH60) which have
been set aside for model aircraft. These
surface vehicles operate on channels 61
through 75, along with some other channels
in another band.
You should never use one of these
steering-wheel RC transmitters to operate a
model aircraft. Likewise, you should never
attempt to use a dual-stick transmitter,
operating on CH11 to CH60, to control a
surface vehicle. This is a federal law!
Trim Levers: One of the basic controls
you must learn early on involves the use of
trim levers. There is usually one for each
channel number. These trim levers are
located close to the transmitter control
sticks. They usually follow the same path as
the control stick. On the right stick
assembly below the stick there will be a
small protruding lever that moves left or
right, duplicating the same motion as the
rudder-control stick. This lever will be tied
to the left-to-right steering action which
62 MODEL AVIATION
Big is Better and Safer too!
The IMAA is an international organization was formed April 10,
1980 to promote non-competitive, educational, safe, relaxed flying
of LARGE radio controlled model aircraft throughout the world.
We are the largest Academy of Model Aeronautics (AMA) Special
Interest Group and as such, are committed to representing the
interest of our members in AMA related matters.
Members enjoy the privilege of
participation in hundreds of Fly-ins
and Rallies each year – including
IMAA’s own Rally of Giants).
Don’t wait. Join today! For complete
membership details, visit our web site
(www.fly-imaa.org) or give us a call
toll free at – 866 366-4622.
High-Flight,
the publication of the IMAA, is
published quarterly and is sent to
all members. High-Flight is
dedicated to the advancement of
large r/c aircraft by concentrating
on new products, techniques, and
innovations developed through
the activities of IMAA Chapters
and individuals around the world.
04sig2.QXD 1.23.03 1:26 pm Page 62
April 2003 63
might be rudder or aileron, depending on
your application.
When you move this lever, the neutral
position of the rudder control surface
shifts slightly. Full excursion of a trim
lever generally imparts a total of 15% of
the normal control throw. The idea of
using trim is to be able to “zero out” your
aircraft’s attitude in flight so that it will
track straight and level with your hands off
the control stick. Full-scale aircraft have
the same type of trim control.
Most beginner and basic sport-type RC
transmitters use a basic mechanical-type
trim function. The levers have a light
detent action that helps hold the last trim
position. The lever’s position can usually
give you an idea of how much trim is
being employed and to which side (left or
right, up or down, etc.). Some newer RC
transmitters employ a digital-type trim
function. You probably won’t see this on a
basic system, so I’ll leave that discussion
for another chapter.
Servo-reversing switches are another basic
control feature. In subsequent installments
you will read about many extra control
features. Some are even available on basic
radio systems, but we want to give you this
information gradually so you can absorb
everything.
Servo reversing can be found on almost
any RC transmitter, and it can be a real
convenience. Somewhere on your
transmitter case—in the lower front
(exposed or under a flip cover), at the rear,
or even under the battery pack—you will
find a series of tiny switches—one for each
channel function. Flipping one of these
switches will reverse the direction of a servo
located inside your model.
Why is this important? When you make
that initial control installation in your
model, the first time you power up the
system you might find that your left rudder
is actually going right and vice versa. If
you have servo-reversing switches, you
can flip the switch for the channel
involved and the servo will switch
directions. Then when you apply left
rudder at the control stick, the rudder will
move for left control on the aircraft. There
will be more about this later.
That concludes this installment. As basic
as all this may sound, I’m sure you will
have many good questions. We learn from
asking questions and getting the right
answers. This sort of thing is done on
Web-site chat groups; that kind of service
may be offered eventually. In the
meantime, write your specific questions to
“From the Ground Up” in care of Bob
Hunt, Box 68, Stockertown PA 18083; Email:
[email protected].
Along with the monthly articles in this
series I hope to publish product reviews
covering items that would especially be of
interest to the RC beginner. This would
include such things as basic RC systems,
ARF (Almost Ready-to-Fly) training
models, basic model engines, personalcomputer
simulators, training programs,
field-support equipment, etc.
As this series progresses, Model Aviation
hopes to publish articles about constructing
models from kits. Later it expects to go
further and publish construction articles for
simple aircraft trainer designs so the
beginner can get the thrill and experience of
building a model from raw materials (like
from scratch!).
The photos accompanying this article
were taken with equipment in my
possession. The fact that a particular brand
is not shown should not be construed as a
“rating” on my part. At the end I have listed
all the RC manufacturers, their addresses,
and their Web sites when available. All the
RC systems work well and are easily on par
with one another. Your purchasing
decisions will likely be predicated on your
personal requirements rather than the brand
name.
Next month I will get into RC-system
installations, system operation, and briefly
discuss some of the more advanced systems.
I also expect to cover purchasing
aftermarket-type RC components to be able
to operate more than one aircraft from one
transmitter. MA
Bob Aberle
Sources:
Airtronics Inc.
1185 Stanford Ct.
Anaheim CA 92805
(714) 978-1895
[email protected]
www.airtronics.net
FMA Direct
5716A Industry Ln.
Fredrick MD 21704
Sales: (800) 343-2934
Tech/service: (301) 668-7615
Fax: (301) 668-7619
[email protected]
www.fmadirect.com
Futaba Corporation of America:
Distributed exclusively in the US, Canada,
and Mexico by Great Planes Model
Distributors
Box 9021
Champaign IL 61826
www.futaba-rc.com/index.html
GWS:
Balsa Products
122 Jansen Ave.
Iselin NJ 08830
(732) 634-6131
balsapr.com
Hitec RCD
12115 Paine St.
Poway CA 92064
(858) 748-6948
www.hitecrcd.com
JR Remote Control/Horizon Hobby Inc.
4105 Fieldstone Rd.
Champaign IL 61822
(217) 355-9511
Maxx Products International, Inc.
815 Oakwood Rd. Unit D
Lake Zurich IL 60047
(847) 438-2233
Ordering only—toll free: (800) 416-MAXX
(6299)
Fax: (847) 438-2898
www.maxxprod.com/
Multiplex USA—now Royal Hobby
Distributors
8295 Tujunga Ave.
Sun Valley CA 91352
(818) 771-1003
www.multiplexrc.com
Polk’s Hobbies/LMP, Inc.
698 S. 21st St.
Irvington NJ 07111
(973) 351-9800
Fax: (973) 351-9700
www.polkshobby.com
Tower Hobbies
Box 9078
Champaign IL 61826
(800) 637-6050
www.towerhobbies.com
04sig2.QXD 1.23.03 1:26 pm Page 63

ast month I introduced the subject of
learning model aviation “from the
ground up.” As the name implies, this is
a beginner series that will be devoted to
people at the entry point of our
wonderful hobby. The sequence of
articles planned for this series follows a
logical order to allow you to enjoy the
learning process. After all, it is a hobby
and it is supposed to be fun.
Since approximately 90% of modelflying
enthusiasts resort to Radio
Control (RC) systems for flight control,
this was judged the best starting place.
The article has literally been developed
from square one. If you already have
some knowledge of RC devices, you
might consider our presentation too
basic. We will try to describe all aspects
of RC for the benefit of the entry-level
hobbyist.
What Does an RC System Do? The
basic idea is that you—the pilot—stand
on the ground holding a radio
transmitter. The transmitter operates as
any broadcasting-type device, except in
this instance voice is not transmitted; a
coded signal is sent to the model aircraft
up in the air.
Onboard that aircraft is a radio
receiver that receives these coded
signals without the need for
interconnecting wires. The received
signal is decoded or processed then
passed on to individual motor-driven
actuators (servos)
that physically
move the aircraft
control surfaces and
adjust (or change)
the engine speed
settings (known as
throttling). The
radio transmitter
(which the pilot
holds) and the
receiver/servos in
the model are
powered by
batteries. So as a
newcomer, you
must become
familiar with the RC
system and the
batteries that power
it.
The entire thrill
of RC flying is the
ability to control the
model’s attitude in
flight, sometimes at
distances of several
hundred feet away, maneuvering the
airplane and landing it close by, just like
a full-scale aircraft. Judgment,
experience, and skill development enter
the equation when it comes to the model
aircraft’s flight.
The First Thing You Should Do:
Before you purchase anything, you owe
it to yourself to visit a local RC flying
field. A hobby dealer in your area
should be able to steer you in the right
direction. A referral to a local RC club
can also prove helpful. The idea is to get
you and possibly other family members
out to see these models in flight
firsthand.
You may be able to talk with some
Radio Control
L
New Hitec RCD Neon three-channel FM RC is interesting
concept; buy basic system, then buy add-on features as
flying skills improve. Transmitter is in background;
charger is on left; receiver and battery box are in center;
two servos are on right. This system, as a basic offering,
comes with two servos and battery box that can hold
four alkaline-type nonrechargeable batteries.
Hitec Neon three-channel FM airborne components (that go inside model). Receiver is at
top; below is four-cell battery box intended for nonrechargeable alkaline cells; two HS-
81 miniature servos are at right. This type of lightweight RC system is intended for small
glow-powered models (.049-.15) and park-flyer electric-powered models.
Typical RC system—Hitec Laser 6 (sixchannel
function transmitter with four
servos)—as it arrives in Styrofoam
shipping container. Transmitter is at
bottom; four servos are at top. Included
are receiver, battery charger.
54 MODEL AVIATION
04sig2.QXD 1.24.03 8:52 am Page 54
of the experienced fliers and get a rough idea
of what is involved. These same people
should be able to make initial
recommendations concerning types of RC
systems, popular system brand names, model
aircraft suitable for initial flight instructions,
engines to power the airplanes, and the
necessary supporting equipment to get you
started. All of these elements will be
discussed in-depth as this series grows month
by month.
How Are RC Systems Classified? RC
systems in the most basic sense provide
control of the aircraft rudder (for steering left
and right), elevator (for pitch control or up
and down motion), and engine throttle
(control engine speeds from idle up through
full power). Each of these basic flight-control
functions is classified as a channel function
(rudder, elevator, and throttle). Keeping that
in mind, RC systems are classified by the
number of channel functions offered—two,
three, four, and in the cases of the most
advanced systems, upward of eight to 10.
When you go out to shop for your first
new RC system, you will see a few basic
two-channel systems (rudder and elevator);
they are only suitable for flying model gliders
or sailplanes, where engines are not
employed, therefore a throttle is unnecessary.
Since two-channel function control is limited
in application, the initial point of
consideration when buying your first radio is
a three-channel-function RC system.
A three-channel RC system provides basic rudder, elevator, and
engine control (sometimes called throttle). Several manufacturers,
including Futaba and Hitec, make excellent, easy-to-use threechannel
RC systems which are also inexpensive. Since so much can
be done with a three-channel RC system, it will probably never
become obsolete. Many of us who fly sophisticated radio systems
still own and regularly use three-channel systems because they are
easy to operate.
Looking ahead, there are four-channel RC systems which
comprise the most popular category. With four channel functions, the
added control is ailerons, which are located on the wing and permit
the model to bank in flight. By adding aileron control to rudder,
elevator, and engine control, you have essentially the same form of
control as used on full-scale aircraft. As you progress in the RC
hobby, you will sooner or later want to expand your horizons and use
all four basic channel functions.
Your first choice for an RC system should be a three-channelfunction
radio. That will hold your initial investment to a minimum.
If you enjoy the hobby and want to grow with it, it would be best if
your second radio system were what we call a “full four-channel”
system.
RC-System Operating Frequencies: After selecting the number of
channel functions, your next choice is what frequency to operate on.
This discussion is most important because it involves a basic safety
requirement you must always observe as an RC pilot.
Years ago the model-aircraft hobby was granted a series of 50
April 2003 55
Systems ■ Bob Aberle
Pen points to three-channel RC transmitter’s control stick. Side-to-side motion provides
rudder steering control; fore-and-aft motion controls model’s pitch (up and down).
Comparison of RC receiver, servo sizes. Top left: Hitec RCD
eight-channel receiver capable of controlling models up to large
sizes—1⁄4 scale and up. Top right: Typical- or average-size Hitec
HS-422 servo can easily control models with up to 60-size glow
engines. (These are components from Hitec Laser 6 system.)
Bottom left: Hitec Electron 6 receiver weighs slightly more than
1⁄2 ounce! Companion miniature HS-81 servo is at bottom right.
This receiver, servo is ideal for smaller glow-powered models
and small electric park flyers. (These components are from Hitec
Neon three-channel FM RC system.)
The Real
Basics
04sig2.QXD 1.24.03 9:04 am Page 55
specific frequencies for RC use by the
Federal Communications Commission
(FCC). Just as the FCC assigns radio and
television stations, it has assigned our
frequencies which exist in a band that runs
from 72.000 megahertz (MHz) to 73.000
MHz. Each of the 50 FCC-approved
frequencies (such as 72.010 MHz, 72.030
MHz, etc.) has been assigned a “channel
number” for easy identification purposes.
The term “channel number” has nothing
to do with the channel control functions I
just discussed. I mention this because that
point has caused initial confusion for many
beginners.
Each RC channel (number) is
essentially the same as a radio-station
number or call sign. If you purchase an RC
system on channel 11, it will broadcast a
signal on that exact channel (or frequency).
In this regard, channel number and
frequency are one in the same.
When you purchase your radio system,
there will probably be a label on the box
containing the frequency (expressed in
MHz, such as 72.010 MHz) and its
equivalent channel number (in this case
CH11). When you open the box, the RC
transmitter and receiver will probably be
stamped with the operating frequency and
the channel number.
Keeping this in mind, RC receivers on
the same frequency/channel can receive the
same signal. This is important. If you own
an RC system that operates on CH11 and
another modeler shows up at the flying
field with the same channel number, you
can’t operate or fly at the same time.
Attempting to do so will lead to possible
radio interference and could result in one or
both models crashing. This is your first
safety lesson as an RC pilot.
If two modelers show up at the field
using the same channel, each must wait his
or her turn so that only one model is
operated at a time. To simplify the control
of these RC channel numbers, a two-digitnumbered
flag is supplied with every RC
system. That flag must always be
Pen points to the rudder trim lever, which is explained in the text.
Rear of Hitec three-channel transmitter shows two servo-reversing switches. This
system’s third, or throttle, channel function doesn’t have servo-reversing capabilities.
Pen points to third channel lever, on rear
of Hitec three-channel transmitter. Index
finger of left hand moves this lever. It
controls engine speed (throttle control).
This crystal controls RC transmitter operating frequency; it is located at rear of case.
Note reference to channel number (CH38), operating frequency (72.550 MHz).
Photos courtesy the author Graphic Design by Lydia Whitehead
56 MODEL AVIATION
04sig2.QXD 1.23.03 1:23 pm Page 56
April 2003 57
Channel-number flag or placard is attached to lower portion of
transmitter antenna. Flag must always be displayed at flying field
for channel-identification purposes—a primary safety rule!
Pen points to transmitter power switch. This is how you turn
transmitter on, off. Directly above switch are three colored lightemitting-
diode (LED) indicators that tell battery status. If top
green LED is glowing, battery is okay. If middle yellow LED
lights, recharge or charge batteries soon. If red is glowing, do
not fly until you tend to batteries. Sometimes colored indicators
are replaced by meter or LCD (Liquid Crystal Display)-screen
voltage readout on more sophisticated transmitters.
Same information as above is posted on Hitec RC transmitters.
Excellent placard on side of Hitec receiver gives channel
number, operating frequency, and clearly states that it’s not for
surface use, such as cars and boats.
prominently displayed on the transmitter antenna for all to see. More
will be written about flying-field safety procedures, but for now I
want you to know about the basic controls that are usually in effect
throughout our country.
Each RC flying field usually has a display board that contains a
group of numbered clothespins or clips. There will be 50 of these
pins or clips running from CH11 to CH60. The drill is simple; when
you want to turn on your RC transmitter at the field, you must first
go to this channel-control board. If the clip for your channel is on the
board, that means it is not in use. Remove that clip and attach it to
the transmitter antenna. At this point you may turn on the power to
that transmitter for test or flying purposes.
While you are “on the air,” if any other modeler intends to
operate on the same channel number and goes to the board, the
missing clip will alert him or her that that RC channel is in use. That
person must wait until you are finished flying, have turned off your
Hitec three-channel, single-stick transmitter operates on AM
mode (details in text). Grip transmitter case with left hand. Index
finger of left hand operates throttle on top rear of case. Right
hand grips single control stick for steering, elevation control
(rudder, elevator).
04sig2.QXD 1.23.03 1:25 pm Page 57
transmitter, and have returned the channel clip to the control board.
It’s a simple drill, but if followed faithfully it will prevent any chance
of interference or model crashes. There are more detailed subtleties to
these procedures, but I will leave that until later.
FM, PCM, and AM Modes of Transmission: Since we are dealing
with “radio,” you should be familiar with the terms “AM,” or
Amplitude Modulation, and “FM,” or Frequency Modulation, when it
comes to listening to broadcast radio stations. Except for the station
numbers or call signs, you can usually receive both broadcast modes
on the same radio, and for the most part they sound the same. Sure
there are subtle differences, but the bottom line is that they serve the
same purposes.
In the RC hobby we can use AM, FM, and a special form of FM
called “PCM,” or Pulse Code Modulation. The most popular
operating mode today is FM—much like in broadcasting. The
majority of RC systems sold are FM; it has been that way for the last
20 years. FM provides good, reliable control and can be purchased at
reasonable prices. Few RC systems are still offered on AM.
Some sophisticated RC systems are offered on a special PCM
mode. It adds a proprietary digital code on top of the FM signal, such
that it can offer more protection from outside interference. PCM-type
modulation is only found on the more advanced and more costly
systems.
As a beginner, the one important thing you must keep in mind is
that you can’t mix modulation types between a transmitter and
58 MODEL AVIATION
RC systems come with servo-mounting hardware, extra output
arms (a bag for each servo supplied), frequency-flag set
(bottom).
Typical four-channel airborne RC system goes into average- to
larger-size model. Top: Aileron extension cable, switch harness,
four servos. Bottom left: receiver. Bottom right: four-cell Ni-Cd
rechargeable battery pack. Components weigh roughly 12
ounces; will fly 20- to 60-powered and medium to large electricpowered
models.
Hitec RCD Laser 6 is full four-channel RC system—a step ahead
of basic or beginner’s radio. Transmitter has six-channel
capability; receiver has at least six channel functions. System
comes with four servos to cover four basic flight-control
functions. It costs less than $200 and will serve well for many
years as you progress from beginner through expert!
Standard RC-system dual-output battery charger. Wall-plug
transformer goes in 115VAC outlet. Output cable at left plugs into
transmitter charging jack; cable on right goes to charging jack or
connector on model.
04sig2.QXD 1.23.03 1:26 pm Page 58
April 2003 61
receiver. An FM transmitter will only
operate an FM receiver, and only if both are
on the same frequency (or channel number).
You will never be able to have an FM
transmitter operate an AM receiver or vice
versa.
Taking this a step further, PCM RC
systems must be of the same type and
manufacturer. Each manufacturer employs
different digital codes. Even within a
manufacturing company, several codes
relating to control resolution might be
indicated (such as the expression 512 PCM
and 1024 PCM). For now let’s concentrate
on regular FM, which is in the majority.
Remainder of RC System Components: So
far we have discussed only the RC
transmitter. When you purchase a full RC
system, included in the box will be what we
call the “airborne components” (the
equipment that must go in your model) and
supporting equipment necessary to make the
system operate.
Airborne RC equipment includes the
receiver, a set of servos (usually one for each
channel control function), a battery pack, a
switch harness—usually with a charging
jack—and an aileron extension cable.
A four-channel-function RC system will
usually be supplied with four servos. On
some economy-priced systems, you might
see a four-channel transmitter with only
three servos supplied. This would allow you
to start with three channel functions at a
slightly lower price, then you could purchase
that fourth servo later. I mention this
marketing technique so you are not surprised
when you open your first system box.
The aileron extension cable is supplied
because in most cases the aileron servo is
mounted in the wing structure. The receiver,
located in the model’s fuselage, may be
farther away than the regular servo cable
length. The extension cable comes in handy
for this application. Almost all RC systems
include servo-mounting hardware and extra
output arms (for different applications).
In addition to the airborne components,
you will receive an all-important dual-output
battery charger. Some basic, inexpensive RC
systems are supplied for use with alkaline,
nonrechargeable batteries. Although these
systems work well, this can cost more
money in the long run. For that reason, most
RC systems are supplied with nickelcadmium
(or Nickel Metal Hydride)
rechargeable batteries.
Generally, eight cells are installed inside
the transmitter and four more are used inside
the model. Systems that include rechargeable
batteries also provide the necessary charger.
Most chargers are wall-plug devices. You
plug the transformer (black box) into a
115VAC electric outlet. Two cables exit the
charger; one goes to the transmitter and the
other goes to a charging jack, which you
may be able to locate externally on the side
of the aircraft fuselage. Leaving this charger
plugged in overnight will completely charge
both battery packs.
The other RC-system supporting items
include the frequency or channel-number
identification flag (already discussed) and
hopefully a well-written (most are) operating
instruction manual.
Sizing RC-System Components to the
Expected Size of Your Model: Another
choice when buying an RC system is the size
of the airborne components. In RC we can
have Giant Scale models that weigh upward
of 20-40 pounds and we can have what we
classify as “park flyers”: models weighing
roughly 6-10 ounces. The larger models can
employ larger and heavier receivers, servos
with strong outputs to move the large control
surfaces, and battery packs of high capacity
that can cope with the required extra power.
Large RC components such as this might
weigh 20 ounces or more; that would be
twice the weight of an entire park flyer. The
size of the airborne RC components must be
geared toward your specific model
requirements. The average RC system
generally includes airborne components that
weigh approximately 10-12 ounces which
are capable of flying average models ranging
from 20-size engine power upward of 60-
size engine power.
If you are interested in starting with parkflyer-
size models, your hobby dealer or
04sig2.QXD 1.23.03 1:26 pm Page 61
distributor should be able to steer you to
substantially lighter-weight equipment for
that application. The purpose of this
discussion is to make sure you don’t
accidentally end up the first time with a 20-
ounce airborne radio that is intended to fly
a 10-ounce total-weight park flyer.
Dual-Stick Transmitter Control:
Throughout the years the popular means of
imparting control-signal commands from
the RC transmitter has been through
“control stick assemblies.” These control
sticks provide two-axis type control; we can
obtain two discrete controls from one stick.
If you grip the stick with the fingers of one
hand and rock it side to side, you can obtain
left or right rudder or possibly left or right
aileron control on the model end. Moving
the stick fore and aft at the same time will
prompt elevator or pitch control, making
the model move up or down.
If you purchase a three-channel RC
system, the transmitter will have a single
two-axis control-stick assembly. This will
provide rudder or aileron control along with
elevator control. A small lever on the front,
side, or rear of the transmitter case will
allow you to operate engine throttle on the
model.
A four-channel RC transmitter will have
two two-axis control-stick assembles. With
this popular configuration you grasp the
transmitter case with both hands such that
each thumb rests on the top of a stick. Each
stick will move in two directions. As you
will soon learn, moving a control stick to a
corner will impart a certain amount of
control to two channels at the same time.
The control will be in proportion to the
amount you displace or move the control
stick. That is why it has always been
referred to as dual, simultaneous
proportional control.
The four-channel transmitter usually has
what we call a Mode II control-stick
configuration. It is safe to say that 99% of
all RC-system transmitters sold are with
that configuration. With respect to the two
control-stick assemblies, the right-side
assembly controls aileron (left or right) and
elevator (up and down). The left-side stick
assembly controls rudder (left and right)
and engine throttle (up and down, or
actually low throttle at the bottom and full
throttle at the top position).
The throttle stick does not have a spring
return to the neutral position, as do the
other three-channel functions. Instead it has
a soft detent effect that makes a clicking
sound as you slowly advance or retard the
throttle. When you take your finger off the
throttle stick, it will stay where you left it.
If you bought a full four-channel RC
transmitter at the start, you could initially
use it to control only three airborne control
functions. In that case the right stick
assembly would operate the rudder and
elevator, and the left stick would only
control the throttle. The fourth channel
function would be ignored.
At your local hobby shop or in RCsystem
catalogs, you may see that certain
transmitters do not have control sticks; they
have steering wheels. These radios have
been designed expressly to control surface
vehicles such as RC cars and boats. Per
FCC regulations, they do not operate on the
50 channels (CH11 to CH60) which have
been set aside for model aircraft. These
surface vehicles operate on channels 61
through 75, along with some other channels
in another band.
You should never use one of these
steering-wheel RC transmitters to operate a
model aircraft. Likewise, you should never
attempt to use a dual-stick transmitter,
operating on CH11 to CH60, to control a
surface vehicle. This is a federal law!
Trim Levers: One of the basic controls
you must learn early on involves the use of
trim levers. There is usually one for each
channel number. These trim levers are
located close to the transmitter control
sticks. They usually follow the same path as
the control stick. On the right stick
assembly below the stick there will be a
small protruding lever that moves left or
right, duplicating the same motion as the
rudder-control stick. This lever will be tied
to the left-to-right steering action which
62 MODEL AVIATION
Big is Better and Safer too!
The IMAA is an international organization was formed April 10,
1980 to promote non-competitive, educational, safe, relaxed flying
of LARGE radio controlled model aircraft throughout the world.
We are the largest Academy of Model Aeronautics (AMA) Special
Interest Group and as such, are committed to representing the
interest of our members in AMA related matters.
Members enjoy the privilege of
participation in hundreds of Fly-ins
and Rallies each year – including
IMAA’s own Rally of Giants).
Don’t wait. Join today! For complete
membership details, visit our web site
(www.fly-imaa.org) or give us a call
toll free at – 866 366-4622.
High-Flight,
the publication of the IMAA, is
published quarterly and is sent to
all members. High-Flight is
dedicated to the advancement of
large r/c aircraft by concentrating
on new products, techniques, and
innovations developed through
the activities of IMAA Chapters
and individuals around the world.
04sig2.QXD 1.23.03 1:26 pm Page 62
April 2003 63
might be rudder or aileron, depending on
your application.
When you move this lever, the neutral
position of the rudder control surface
shifts slightly. Full excursion of a trim
lever generally imparts a total of 15% of
the normal control throw. The idea of
using trim is to be able to “zero out” your
aircraft’s attitude in flight so that it will
track straight and level with your hands off
the control stick. Full-scale aircraft have
the same type of trim control.
Most beginner and basic sport-type RC
transmitters use a basic mechanical-type
trim function. The levers have a light
detent action that helps hold the last trim
position. The lever’s position can usually
give you an idea of how much trim is
being employed and to which side (left or
right, up or down, etc.). Some newer RC
transmitters employ a digital-type trim
function. You probably won’t see this on a
basic system, so I’ll leave that discussion
for another chapter.
Servo-reversing switches are another basic
control feature. In subsequent installments
you will read about many extra control
features. Some are even available on basic
radio systems, but we want to give you this
information gradually so you can absorb
everything.
Servo reversing can be found on almost
any RC transmitter, and it can be a real
convenience. Somewhere on your
transmitter case—in the lower front
(exposed or under a flip cover), at the rear,
or even under the battery pack—you will
find a series of tiny switches—one for each
channel function. Flipping one of these
switches will reverse the direction of a servo
located inside your model.
Why is this important? When you make
that initial control installation in your
model, the first time you power up the
system you might find that your left rudder
is actually going right and vice versa. If
you have servo-reversing switches, you
can flip the switch for the channel
involved and the servo will switch
directions. Then when you apply left
rudder at the control stick, the rudder will
move for left control on the aircraft. There
will be more about this later.
That concludes this installment. As basic
as all this may sound, I’m sure you will
have many good questions. We learn from
asking questions and getting the right
answers. This sort of thing is done on
Web-site chat groups; that kind of service
may be offered eventually. In the
meantime, write your specific questions to
“From the Ground Up” in care of Bob
Hunt, Box 68, Stockertown PA 18083; Email:
[email protected].
Along with the monthly articles in this
series I hope to publish product reviews
covering items that would especially be of
interest to the RC beginner. This would
include such things as basic RC systems,
ARF (Almost Ready-to-Fly) training
models, basic model engines, personalcomputer
simulators, training programs,
field-support equipment, etc.
As this series progresses, Model Aviation
hopes to publish articles about constructing
models from kits. Later it expects to go
further and publish construction articles for
simple aircraft trainer designs so the
beginner can get the thrill and experience of
building a model from raw materials (like
from scratch!).
The photos accompanying this article
were taken with equipment in my
possession. The fact that a particular brand
is not shown should not be construed as a
“rating” on my part. At the end I have listed
all the RC manufacturers, their addresses,
and their Web sites when available. All the
RC systems work well and are easily on par
with one another. Your purchasing
decisions will likely be predicated on your
personal requirements rather than the brand
name.
Next month I will get into RC-system
installations, system operation, and briefly
discuss some of the more advanced systems.
I also expect to cover purchasing
aftermarket-type RC components to be able
to operate more than one aircraft from one
transmitter. MA
Bob Aberle
Sources:
Airtronics Inc.
1185 Stanford Ct.
Anaheim CA 92805
(714) 978-1895
[email protected]
www.airtronics.net
FMA Direct
5716A Industry Ln.
Fredrick MD 21704
Sales: (800) 343-2934
Tech/service: (301) 668-7615
Fax: (301) 668-7619
[email protected]
www.fmadirect.com
Futaba Corporation of America:
Distributed exclusively in the US, Canada,
and Mexico by Great Planes Model
Distributors
Box 9021
Champaign IL 61826
www.futaba-rc.com/index.html
GWS:
Balsa Products
122 Jansen Ave.
Iselin NJ 08830
(732) 634-6131
balsapr.com
Hitec RCD
12115 Paine St.
Poway CA 92064
(858) 748-6948
www.hitecrcd.com
JR Remote Control/Horizon Hobby Inc.
4105 Fieldstone Rd.
Champaign IL 61822
(217) 355-9511
Maxx Products International, Inc.
815 Oakwood Rd. Unit D
Lake Zurich IL 60047
(847) 438-2233
Ordering only—toll free: (800) 416-MAXX
(6299)
Fax: (847) 438-2898
www.maxxprod.com/
Multiplex USA—now Royal Hobby
Distributors
8295 Tujunga Ave.
Sun Valley CA 91352
(818) 771-1003
www.multiplexrc.com
Polk’s Hobbies/LMP, Inc.
698 S. 21st St.
Irvington NJ 07111
(973) 351-9800
Fax: (973) 351-9700
www.polkshobby.com
Tower Hobbies
Box 9078
Champaign IL 61826
(800) 637-6050
www.towerhobbies.com
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