From the Ground Up - Advanced RC Systems - 2004/02

46 MODEL AVIATION
Advanced
THIS IS MY 10TH
installment in this initial
phase of the “From the
Ground Up” series. I’ll
be back next month with
some frequently-asked
questions and in the
April issue the emphasis
will shift to fueled models under Frank
Granelli’s expert tutelage.
At the beginning of this series I
discussed some of the basic Radio
Control (RC) systems as an overall
introduction to the model-aircraft
hobby. To keep it simple and
inexpensive, I selected a basic threechannel
transmitter with a single
control stick. I use several of these
systems for my flying, so please don’t
worry; I didn’t recommend that you
buy something that would quickly
become obsolete.
As the series progressed I described
the Hitec Neon three-channel system,
then the electric power system, and
then the Aero Craft Pogo as a firsttime
(Almost Ready-to-Fly) training
aircraft.
My student Jay Federman had
already done a bit of flying on his
own, and he owned a four-channel,
dual-stick RC transmitter. When we
flew the Pogo for the first time, using a
trainer cable, Jay had to hold the Neon
transmitter since it was the one
broadcasting the signal. The master
control was my transmitter (a dualstick-
assembly four-channel unit),
which I held as the instructor pilot.
Jay got confused because the
throttle lever is on the rear of the case
(of the three-channel transmitter) and
it operates with a side-to-side motion.
He had done some flying using a leftside
control stick that moved up for
high speed and down for idle speeds.
I recognized this problem right
away, and many readers wrote in to
“scold” me for having suggested a
three-channel RC transmitter to a
beginner. Admittedly, as you progress
to four-channel (“full house,” as we
call it: elevator, aileron, rudder, and
throttle control), the throttle control
will be on the left stick and is operated
with an up-and-down motion.
I guess some apologies are in order.
Just keep in mind that the threechannel
RC system will never become
obsolete. It is well suited for my RC
sailplanes, parking-lot flyers, and
indoor RC.
I’m getting into more advanced RC
systems at this time because eventually
you will want to, and when you do you
will quickly appreciate some of the
extra features they can offer. You will
also be pleased to know that many of
these advanced radios are simple to
operate and are comparatively
inexpensive. So let’s get into it.
A basic RC transmitter, be it a threeor
four-channel-function unit, will not
be what we call a “computer” or
microprocessor-type radio. It will not
have a Liquid Crystal Display (LCD)
screen that allows you to set the
special commands or controls.
Most basic transmitters have servo
reversing, and a few might even offer
dual rate control on two-channel
functions. Servo direction is usually
changed with the flip of a tiny switch
(unplugging and rotating a cable on the
Hitec Neon). Dual rate control cutback
is adjusted by rotating a small
potentiometer control (dial). These
basic radios have a few switches and
potentiometers (dials) but no internal
computer circuitry and certainly no
New Airtronics VG6000A is popular
entry-level computer RC transmitter. It
will be featured in an MA product
review in the future.
02sig2.QXD 11/25/03 12:59 pm Page 46
memory circuits.
An advanced RC transmitter has an
internal computer chip that contains a
great deal of stored program information
in its memory circuits. It can also store
your control inputs, allowing you to
operate several models from a single
transmitter.
You can tell that it is a computer-driven
system because it has an LCD screen on
the front of the transmitter case. (One
exception is the FMA Direct T-80RF,
which is just a small step up from a basic
unit). The LCD screen displays a variety
of parameters; some are basic and
preplanned for you, and others you can
call up from a menu system that is
programmed into the transmitter.
How you access these menus, make
changes, and store the new inputs in the
memory is what an advanced RC
transmitter is all about. Once learned, you
February 2004 47
RC Systems
Typical RC transmitters (L-R): Hitec Neon three-channel (single
control stick); Hitec Laser 6, which has two control-stick
assemblies but is basic—not a computer radio; Futaba T6EXA
entry-level computer radio; Hitec Laser 6, which is computer
driven and has channel synthesizer.
L-R: Futaba T6EXA computer transmitter is covered in text. Hitec
Eclipse transmitter can be set for high or low FM deviation and
with Spectra synthesized module can dial up any of 50 RC
channels for models. Polk’s Tracker II has all Eclipse features,
but you don’t have to remove module to change channels.
Left: Rear of Hitec Neon three-channel single-stick transmitter.
Pointer shows location of throttle-control lever which must be
moved side to side to adjust engine/motor speeds. Right: Futaba
T6EXA computer transmitter, which has two control-stick
assemblies. Throttle control is obtained from left stick and
operated in up-and-down movement (for high and low throttle
settings).
Futaba T6EXA is roughly $180 from Tower
Hobbies. Full system has receiver, four
servos, full Ni-Cd battery packs.
by Bob Aberle
The JR XP662 distributed by Horizon Hobby is a popular entrylevel
Radio Control computer transmitter.
Photos courtesy the author
d
02sig2.QXD 11/25/03 12:59 pm Page 47
will have many more control features available for your use. You
can start with an advanced RC transmitter, but use only basic
controls until you gain a certain amount of experience.
Before I get into a computer-driven RC transmitter’s inner
workings, I must mention several more facts. Most modern RC
systems broadcast their signal on frequency modulation (FM).
Only a few amplitude modulation (AM) radio systems are still on
the market, and they are gradually disappearing.
You can’t intermix signals with these systems. An FM RC
transmitter can’t operate an AM RC receiver. Even within the FM
category, there are two types of signals that various manufacturers
employ. One is called FM deviation on the “low side.” Futaba,
Hitec RCD, FMA Direct, and GWS make use of this type of
signal. There is also FM deviation on the “high side,” as exhibited
in radios that JR Remote Control and Airtronics manufacture.
Keeping all of this in mind, a Futaba FM RC transmitter can
operate a Futaba FM RC receiver and FM RC receivers made by
Hitec, FMA Direct, and GWS. A JR FM RC transmitter can
operate a JR FM receiver and an Airtronics FM receiver.
Utilizing smart programming techniques, several RC
transmitters are able to select “high” or “low” FM deviation. This
can be a bonus since one transmitter can be used to operate almost
any brand of RC FM receiver on the hobby market, provided it is
on the same frequency (RC channel). Later I will mention an even
more sophisticated RC transmitter that uses a synthesizer which is
capable of dialing up any of the 50 RC channels available for
model aircraft.
I hate to get complicated early on, but in FM RC equipment
there is one other type known as pulse code modulation (PCM). It
is a technique in which a special digital code is added to the FM
signal. It provides much greater interference rejection than regular
FM, but it is usually only offered on the expensive, top-of-the-line
radio systems. These PCM systems also provide a fail-safe feature
that adjusts the controls to preset positions and reduces the engine
throttle if interference is experienced.
You should also know that each manufacturer uses its own
dedicated digital code, so you must stay with one brand for the
transmitter and receiver; you can’t intermix these units.
Types of Advanced RC Systems: You have already been
introduced to the basic radio. There are also “first step” computerdriven
RC transmitters. These entry-level systems offer many
extra control features, are relatively easy to use, and are
comparatively inexpensive (full systems range from $180 to
$250).
Several manufacturers offer a further step into the computerradio
market with systems ranging from $300 to $500. These offer
more features than the first-echelon systems but add a certain
amount of complexity. For the all-out expert competition-minded
pilot, there are top-of-the line radio systems that cost as much as
$1,000 and more. That won’t be for you for some time yet!
The First-Step Computer-Radio System: All of the popular RC
manufacturers—including Airtronics, FMA Direct, Futaba
(Hobbico), Hitec RCD/Multiplex, and JR (Horizon Hobby)—have
these entry-level computer-radio systems. Some of the big mailorder
hobby companies also offer “house radios,” but they are
generally made by the manufacturers I just listed.
The model numbers of these first-step radios are important for
identification purposes. For instance, the Airtronics VG6000 has a
new, innovative menu system. I expect to review this radio in
Model Aviation in the near future.
The Futaba T6EXA is simple and affordable (roughly $180!),
and this is the one I will explain in depth in a moment. Also
popular are the Hitec RCD Flash 5 X and Eclipse models and the
JR XP662. I have to admit that at this time I have little experience
with the new Hitec/Mulitplex systems from Europe.
You do not need to use any of the special features on these
first-level computer radios right away. You can turn off or inhibit
the extras while you learn to fly your first few RC models.
Futaba T6EXA: The heart of any computer-radio system is the
transmitter, and that is what I will discuss. Refer to the photos as I
proceed. Some photos are of the LCD screen on the T6EXA
transmitter, and others are of the illustrations in the Futaba
instruction manual (for added clarity).
Most RC-system manufacturers include their instruction
manuals on their Web sites. They are posted as PDFs (Portable
Document Formats) for viewing, or even printing, purposes. You
can access the Futaba T6EXA manual at www.futabarc.
com/manuals/6exa-manual.pdf.
The six-channel-control-function Futaba T6EXA transmitter
offers:
• low-voltage alarm
• digital trims
• six model memory positions
• the ability to reset any memory slot to the factory-default
positions
48 MODEL AVIATION
Upper left portion of Futaba T6EXA transmitter case. Switch on front
is for “CH.5 GEAR”—a nonproportional auxiliary channel. At top left
corner is “TRAINER/THT CUT”: a momentary contact switch you
pull forward to operate; when you let go, it springs back rearward. It
operates trainer cable function or can kill a glow-fueled engine.
Top right corner of transmitter case. “AIL/ELEV D/R” switch
turns dual rate, exponential rate control on or off. On top is
“CH.6 FLAPS” knob you turn to operate proportional sixth
channel function. You can use it to operate flaps, spoilers, or any
other auxiliary function.
02sig2.QXD 11/25/03 1:00 pm Page 48
Lower front part of Futaba T6EXA has LCD screen, control
necessary to operate built-in computer system. To left of screen
are “MODE,” “SELECT” switches. At right is “DATA INPUT”
switch; it rocks up or down for + or – control inputs. Each
channel function (six total) is listed next to DATA INPUT switch.
To enter menu system, turn on power then press and hold down
MODE and SELECT switches for roughly two seconds. “MODEL”
memory position (1 through 6) is first item to come up and will
flash. Press DATA INPUT switch to scroll around six positions.
This is how you select correct position to operate each model.
If you press SELECT while in MODEL portion of menu, letters
“CL” will flash on screen. Press DATA INPUT switch in either
direction (+ or –) and hold for a second to erase all control inputs
to this position and restore them to factory settings. This is
especially helpful when setting controls for new model.
This is the typical screen for reversing the servo direction for any
of the six channel functions.
When you initially turn on transmitter, basic screen display will
appear. Small “1” in upper right corner is current model-memory
position. Larger “8.5v” is transmitter battery voltage. At 8.5 volts,
audible alarm will sound and battery icon on screen will flash,
telling you to stop flying and recharge battery.
Since you can’t name models on LCD screen, Bob pastes list to
rear of transmitter. You could also put a note on your model,
such as “Futaba T6EXZ, No. 1”. That way you would be alerted to
take correct transmitter to field and make sure it is set on model
memory position 1.
February 2004 49
02sig2.QXD 11/25/03 1:01 pm Page 49
• dual rate control of two channel functions
• exponential rate control of two channels
• endpoint adjustment (EPA) on all channels
• servo reversing on all channels
• trim memory and position
• programmable mixing of any two channel functions
• wing mixing (elevons, flaperons, V-tail)
• throttle cut for glow-engine operation and provision for trainer
cable
It’s all there in that one transmitter case! Keep in mind that six
memory positions means that you can fly as many as six models
from this transmitter.
Looking at the T6EXA’s front panel, you will see the two dual
axis control-stick assemblies. When flying with only three
channels, the right stick operates the rudder and elevator and the
left stick moves up and down for the throttle control. All control
sticks have spring return to the neutral position except the throttle,
which has a ratchet device to hold the last position.
When using four-channel control, the right stick usually has
the aileron and elevator functions and the left stick assembly
provides rudder and throttle. For years this stick configuration has
been called Mode 2. A few pilots (mostly in Europe) still fly what
is called Mode 1. I have no intention of getting into that other
mode at this time, but the T6EXA is capable of Mode 1 control as
explained in the manual if that is your preference.
In addition to the four basic flight controls, a fifth channel is
available to operate a retractable landing gear, as a towhook
release on a sailplane, or as any other auxiliary function you
might think of. It is not a proportional control channel; the servo
goes to one side or the other (no neutral position). The fifth
channel is operated by the “CH.5 GEAR” switch at the upper left
corner of the case.
At the top right corner of the transmitter case is a knob that
proportionally operates a sixth channel function; it is identified as
“CH.6 FLAPS.” This channel is primarily used as a flap or spoiler
control, but, again, you could use it for a variety of auxiliary
functions.
There are several more switches on the front panel. At the
upper right is one identified as “AIL/ELEV D/R.” It
simultaneously turns on or off dual rate control for the
aileron/elevator (or rudder/elevator for three-channel control).
This switch also turns on/off the special exponential rate control
to the same two channel functions.
At the top left corner of the case is a momentary contact
(spring return) switch to operate the trainer-cable function. The
“From the Ground Up” installment in the September 2003 issue
(on page 71) has a more detailed discussion about using a trainer
cable.
When momentarily pulled forward and released, that trainercable
switch will act as an engine-kill (stop) switch. This is
helpful when your transmitter employs digital trim, as does the
T6EXA. By pulling this switch, you don’t have to operate the
throttle digital trim lever to completely kill your glow-fueled
engine. (Frank Granelli will explain this in more depth later in
this series.)
We’ve finally gotten to the computer system. At the lower
50 MODEL AVIATION
Dual rate control allows you to reduce amount of control throw
from 100% to 0%. Then by throwing D/R switch on front panel,
you can obtain reduced control throw in flight. Dual rate control
is only available on CH1 (aileron or rudder) and CH2 (elevator).
While in dual rate menu, if you press SELECT beyond CH2 you
will come to exponential rate control. You will see =/– sign
followed by 0%. As you reduce percentage in negative direction
(“–5,” “–10,” “–15,” etc.), controls react slower around neutral
position, giving “softer” feel in flight. This feature is also available
on CH1 and CH2 and can be combined with dual rate control.
EPA (endpoint adjustment) is probably the transmitter’s most
worthwhile feature and will be popular even with a rank beginner.
It lets you adjust control throw of any servo, and it will let you do
that independently. You can set more up- than down-elevator!
02sig2.QXD 11/25/03 1:01 pm Page 50
portion (middle) of the transmitter case is
an LCD screen. To the left of the screen
are two push-button switches identified as
“MODE” and “SELECT.” To the right is a
data-input switch that moves up (+) and
down (–). Next to this switch the six
channel controls are listed by number and
function, such as “CH1=Aileron,”
“CH2=Elevator,” etc.
When you first turn on the transmitter
power, an initial or basic display will
appear on the LCD screen. It will have a
small number (1 through 6) at the upper
right and a larger number, such as 10.0v, at
the lower right. The smaller number tells
you which computer-memory position is
currently in operation.
The larger number is this particular
transmitter’s battery voltage. At 10.0 volts
or slightly higher, the transmitter battery is
close to full charge. When the voltage falls
to 8.5, an audible alarm will sound and a
battery icon will flash on the LCD screen.
This is a warning to land your model
immediately because you only have
several minutes of charge remaining. At
that point you recharge the battery or
substitute a freshly charged battery pack.
To access the various control features,
you must get into the T6EXA computer
menu. Many of these computer radios have
two menus; one is for basic programming
and selection of the model memory and the
other contains all of the detailed control
features. I chose the T6EXA because it
only has one menu, which makes it simple.
With the transmitter power on, press
the MODE and SELECT switches (keys)
and hold them for a second or two. The
first thing to show up on the LCD screen is
the “MODEL” memory position. A largesize
number (1 through 6) will flash on the
screen. You change the model number by
pressing the data-input (+ or –) switch.
This will allow you to scroll up to 6 or
down to 1.
On some computer transmitters you can
add a model’s name to the memoryposition
number for identification
purposes, but that feature isn’t available on
this unit. As an alternative I pasted a list
on the rear of the case indicating each
model and the number assigned to it.
You must be especially careful when
selecting the correct model-memory
position. If you don’t select the right
number, you may find your controls
reversed and a crash could easily result.
On the other hand, remember that you can
operate as many as six different aircraft
from this transmitter.
While still in the MODEL portion of
the menu, if you press SELECT you will
see a “CL” flash on the LCD screen along
with the model memory-position number.
Pressing either data-input key (+ or –) for
February 2004 51
This is how EPA function looks when called up on LCD screen.
You can select CH1 or CH2, then amount of control-throw
reduction (from 100% to 0%—which you won’t be doing!).
Amount of trim used on any of four main channel functions can
be displayed in this part of menu. Any trim you set in flight is
automatically saved until you change it on later flight. While in
this portion of menu, you can add or subtract trim by following
numerical position displayed on LCD screen.
P.MIX allows you to mix any two channel functions. You could
have small amount of rudder control when applying aileron to
smooth out or coordinate turns. “Inh” indicates that P.MIX is
turned off or inhibited.
W.MIX lets you set up programmed mixing for elevon control,
flaperons, or V-tail operation (as explained in text).
02sig2.QXD 11/25/03 1:01 pm Page 51
52 MODEL AVIATION
roughly two seconds will erase any inputs
stored in that memory position. Controls
will then be restored to factory-default
settings. This can be helpful when you are
setting up controls for a new model.
Moving along the menu, press MODE
and you come to “REVERSE.” This
function will let you reverse any servo’s
direction. Press SELECT to choose the
channel function you want to reverse (1 to
6), and then press + or – to select the
“NOR” (normal) or “REV” (reverse) servo
direction. Press MODE again, and the
“D/R” (Dual Rate) function comes up. The
menu keeps going in one direction, as in a
loop. If you miss an item, keep pressing
MODE until it appears again.
Dual rate control applies only to
channels 1 (aileron or rudder when flying
with three channels) and 2 (elevator). The
LCD screen will show CH 1 or CH 2,
which you choose by pressing SELECT.
Then you will see 100%, meaning that the
control is set for “full,” or maximum
throw. Use the data-input – switch to
reduce the control to something less than
full.
Now that AIL/ELEV D/R switch at the
upper right comes into play. With it in the
down position, you want your aileron or
rudder and your elevator at full throw, or
100%. Move that switch to the upper
position, and the reduced throw that you
just set (something less than 100%) will
appear. Keep in mind that the AIL/ELEV
D/R switch affects the two channels at the
same time on this transmitter; you can’t
separate the aileron and elevator functions.
Dual rate control can be helpful on
faster models. At takeoff and landing
speeds you have the controls set at full, or
100%. During the flight, you can flip the
D/R switch to the up position and the
controls will be reduced somewhat,
making the airplane easier to fly at high
speeds.
When pressing the SELECT switch
while in this same D/R function, after D/R
you will come to an added feature called
exponential rate control. When you get to
this function you will see a plus and minus
sign and 0% on the LCD screen. If you
then press the minus switch, you will see a
negative number such as 5, 8, 10, 15, etc.
These negative numbers make the initial
servo movement less than normal.
What happens is that the control
response is slower or “softer” around the
neutral position. By selecting that negative
number, you can tailor the feel to suit you
and your model. I realize that this sounds
slightly complicated at first, but you will
learn as you gain experience with the
system. Keep in mind that with the
T6EXA you can have dual rate and
exponential rate together or you can have
dual rate or exponential rate separately.
The next menu item (press MODE) is
EPA. This is available on all six channels.
It is especially nice to have EPA on the
throttle channel when using a fueled
engine; it makes high and low carburetor
adjustments so easy.
With EPA you can set the servo control
throw to the exact amount of control
required. You can even set the elevator for
more up than down or more right aileron
than left. This is probably the best feature
in a computer-radio system. It is the
control function you will use the most.
As you go through the menu and make
control adjustments, your inputs are saved
automatically in the computer each time
you move on to the next menu item or if
you turn the power off. Afterward, any
time you call up that particular model
memory position, the control inputs you
made will be right there for you (stored in
the computer memory).
The next menu item is important
because it involves the trim function. Each
of the four main channels has a separate
trim switch. On this transmitter the trim is
the more modern digital variety. The
purpose of trim is to allow you to set your
model for straight and level flight with
your hands off of the control sticks. You
“rocker” the trim switches left or right or
up and down to achieve level flight
characteristics.
Once you have a model adjusted for
level flight, you can call up the “TRIM”
menu item. It will allow you to select any
one of the four channels that provide trim
(aileron, elevator, rudder, or throttle). For
02sig2.QXD 11/25/03 1:01 pm Page 52
Transmitter’s battery-compartment cover has been removed and
battery pack (red case) partially removed. Battery has only 600 mAh
capacity—enough to operate transmitter for roughly two hours.
You could substitute packs with almost double the capacity that
still fit in compartment. If you go to higher capacity, you will have to
buy variable output charger such as ACE R/C DDVC shown.
These are some RC-system connectors with which you may
come in contact. At top is transmitter charging jack. In middle are
mating halves of receiver battery cables (only two wires
employed). At bottom is servo connector with three wires.
Convention today throughout hobby industry is to have negative
pin in middle. If servo connector is plugged in backward (hard to
do!), servo will not work but will not be damaged.
To show you that Bob also thinks about receivers, at top is his
first, from 1953—the Miller—which was featured in MAN that
year. It weighed 5 ounces and offered only single-channel control
of rudder. In middle are typical, current Futaba and Airtronics
dual-conversion RC FM receivers. At bottom right is FMA Direct
aftermarket receiver. At bottom left is popular 0.2-ounce GWS
R4P micro four-channel receiver.
Spectra synthesized module removed from Hitec Eclipse
transmitter. By rotating two dials shown, you can obtain any of
50 channels available for model use on 72 MHz band.
Polk’s Modelcraft Hobbies’ new Tracker II transmitter, companion
Seeker receiver. Transmitter is synthesized to operate on all 50
channels. Scanning receiver inside transmitter listens to see if
channel you chose is clear before it allows it to be turned on.
Seeker can automatically lock onto any channel set on Tracker II.
Tracker II’s LCD screen shows memory position 2, that channel
is set at 52, and exact frequency of that channel. “10.01V” is
transmitter voltage.
February 2004 53
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each function the LCD screen will provide
a numerical trim position. This is strictly
for reference purposes. Remember that
whatever trim you use on a particular
model to achieve level flight will be stored
in the computer and will remain until you
make changes.
On this particular transmitter, the fifth
and sixth channel functions do not have
trim. Also, on the CH 3 throttle function
the trim only operates when the control
stick is down close to minimum throttle.
This is so you can set your fueled engine
carburetor for the lowest possible idle
speed yet not stall the engine. Frank
Granelli will go into this feature.
The remaining menu items cover
certain mixing functions. There is a
programmable mixing (“P.MIX”) circuit
that will let you combine any two control
functions. I like to use this for coupled
aileron and rudder on some models. When
you apply ailerons to bank the model, the
rudder will respond to that single
command.
Several wing-mix (“W.MIX”) functions
can provide such things as elevon control
(“EL”) that will mix aileron and elevator
for flying wings or delta-wing models. The
flaperon (“FP”) function makes both
ailerons drop down for flap-type control. A
V-tail (“V”) mixing function provides a
rudder and elevator effect, as on a Scale
Beechcraft Bonanza. I won’t get into these
mixer functions in any detail because you
probably won’t be using them right away.
Quite a few computer-driven RC
transmitters include multimodel-type
programming; they offer menus
specifically for fixed-wing aircraft, for
helicopters, and in some cases for
sailplanes. This makes for some difficult
menu searching. Also, the switches are
marked three ways, making identification
difficult. I chose the T6EXA radio because
it has one menu and is intended
exclusively for fixed-wing aircraft.
Many of these computer RC
transmitters draw upward of 200 mA of
current. It is still common to see 600 mAhcapacity
Ni-Cd batteries supplied with
these systems, but in today’s hobby market
we are seeing NiMH batteries in the same
AA size with capacities up to 1100 mAh
and more.
Batteries such as these are available
from suppliers such as Batteries America
and SR Batteries. They even provide the
mating connectors for your particular
brand of transmitter. If you want more
capacity with which to operate your
transmitter for longer periods of time,
these higher-capacity replacement packs
are the way to go.
Just remember from my “Battery
Basics” article (in the October 2003 Model
Aviation) that you must charge these
batteries at the rate of C/10 (capacity
divided by 10). An 1100 mAh battery
would have to be charged overnight at 110
mA. To obtain that kind of current you
will need a variable output charger, such
as the Ace R/C Digital Dual Variable
Charger.
A number of computer transmitters
currently on the market employ a
synthesizer: a circuit that allows you to
dial up any one of the 50 channels
available for flying model aircraft. You
can purchase the Hitec Eclipse transmitter
with Hitec’s Spectra synthesized module.
This module plugs into the rear of the
transmitter case. To change channels, you
unplug the module and rotate two tiny
dials to obtain any channel from 11 to 60.
The Eclipse is also one of the
transmitters that lets you select high or low
FM deviation. That means you can operate
any FM RC receiver on the market with
this transmitter (regardless of the deviation
or the channel number).
Polk’s Modelcraft Hobbies has gone
one better with its Tracker II computerdriven
transmitter, which accommodates
more than 90 memory positions. A
synthesizer lets you select any one of the
50 RC aircraft channels using the LCD
screen so you don’t have to remove a
module and twist any dials. You can also
enter the channel number for each model
into the memory along with the proper
deviation.
When you first turn on the Tracker, a
built-in scanning receiver (right inside the
54 MODEL AVIATION
02sig2.QXD 11/25/03 1:04 pm Page 54
transmitter) scans the operating channel
before allowing it to go on the air. The
Polk’s Seeker companion receiver can
listen for an FM signal and then set itself
to that channel. With this concept you
could switch channels every flight and
never have to wait for an available
channel.
The fact that these computer-driven
transmitters can store control data for
many models means that you will need
many more receivers (one for each model)
but only one transmitter. Generally, the
RC manufacturers would like to sell you
an entire system: transmitter, receiver, and
servos. Through the years, many of these
manufacturers have priced airborne packs
(receiver and servos) at practically what it
costs for a full system.
More recently, companies have come
out expressly with aftermarket receivers
and servos that will work from almost any
computer-driven transmitter. FMA Direct
has a complete line of receivers and
servos. It even has a micro-size dualconversion
receiver (the M5) that weighs
0.35 ounce! Using aftermarket
microreceivers and microservos is
commonplace today, especially with
parking-lot and indoor RC flyers.
When mixing and matching computer
transmitters, receivers, and servos, you
will have to contend, to a degree, with
connector polarity. Connectors used on
receivers, switch harnesses, and servos
now follow the same convention.
On three-pin servo connectors, one
outside pin is battery negative, the center
pin is battery positive, and the other
outside pin is the signal. Plug it in one
way, and the servo works. Reverse the
connector (some have keys that prevent
this possibility), and the servo does not
work.
One thing is for sure: you cannot blow
out that servo with this type of polarity
convention. Years ago this was much
more of a problem. The only connector
that is still different is the charger plug on
the JR transmitters; the center pin and
outside connection are different on this
plug than on all others in the RC hobby
industry.
For the More Advanced RC Pilot: Most
of us fly on one of the 50 RC channels that
the Federal Communications Commission
(FCC) has made available expressly for
the control of model aircraft. With 50
channels to choose from and added
features such as synthesizers with dial-up
channel-selection capabilities, you never
have to wait very long to make a flight.
However, you may see certain
concentrations of channels at local flying
fields. One possibility to avoid a “channel
traffic jam” is to obtain an FCC ham radio
license and then operate on the Amateur
Radio Service 6-meter band (50 MHz).
Many RC manufacturers offer systems on
10 channels near 50 MHz.
If you are interested in what it takes to
become a ham and practically be able to
fly on your own channel, contact the
national organization (which is like our
AMA). It is the American Radio Relay
League, 225 Main St., Newington CT
06111; Tel.: (880) 594-0200; Web site:
www.arrl.org.
My articles in this series began with the
March 2003 Model Aviation. Look for
Frank Granelli and the glow-fueled-model
input for months to come. I expect to do
several “guest spots” on subjects such as
parking-lot/backyard flying, indoor RC,
Lithium-Polymer batteries and their
application, and some FAQs (frequently-
56 MODEL AVIATION
asked questions), which will be published
next month.
Keep in mind that this series is posted on
the Model Aviation portion of the AMA’s
Web site, at http://modelaircraft.org/mag/
index.htm. MA
Bob Aberle
Manufacturers:
Ace Hobby Distributors, Inc.
2055 Main St.
Irvine CA 92614
(949) 833-0088
Fax: (949) 833-0003
www.acehobby.com
Airtronics Inc.
1185 Stanford Ct.
Anaheim CA 92805
(714) 978-1895
[email protected]
www.airtronics.net
Batteries America
2211-D Parview Rd.
Middleton WI 53562
(800) 308-4805
[email protected]
www.batteriesamerica.com
FMA Direct
5716A Industry Ln.
Frederick MD 21704
(800) 343-2934
Fax: (301) 668-7619
[email protected]
www.fmadirect.com
GWS (also sold by Horizon Hobby)
Balsa Products
22 Jansen Ave.
Iselin NJ 08830
(732) 634-6131
www.balsapr.com
Hitec RCD (and Multiplex)
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
www.horizonhobby.com
SR Batteries Inc.
Box 287
Bellport NY 11713
(631) 286-0079
Fax: (631) 286-0901
[email protected]
www.srbatteries.com
Tower Hobbies (Hobbico and Futaba
radios)
Box 9078
Champaign IL 61826
(800) 637-6050
www.towerhobbies.com
02sig2.QXD 11/25/03 1:05 pm Page 56

46 MODEL AVIATION
Advanced
THIS IS MY 10TH
installment in this initial
phase of the “From the
Ground Up” series. I’ll
be back next month with
some frequently-asked
questions and in the
April issue the emphasis
will shift to fueled models under Frank
Granelli’s expert tutelage.
At the beginning of this series I
discussed some of the basic Radio
Control (RC) systems as an overall
introduction to the model-aircraft
hobby. To keep it simple and
inexpensive, I selected a basic threechannel
transmitter with a single
control stick. I use several of these
systems for my flying, so please don’t
worry; I didn’t recommend that you
buy something that would quickly
become obsolete.
As the series progressed I described
the Hitec Neon three-channel system,
then the electric power system, and
then the Aero Craft Pogo as a firsttime
(Almost Ready-to-Fly) training
aircraft.
My student Jay Federman had
already done a bit of flying on his
own, and he owned a four-channel,
dual-stick RC transmitter. When we
flew the Pogo for the first time, using a
trainer cable, Jay had to hold the Neon
transmitter since it was the one
broadcasting the signal. The master
control was my transmitter (a dualstick-
assembly four-channel unit),
which I held as the instructor pilot.
Jay got confused because the
throttle lever is on the rear of the case
(of the three-channel transmitter) and
it operates with a side-to-side motion.
He had done some flying using a leftside
control stick that moved up for
high speed and down for idle speeds.
I recognized this problem right
away, and many readers wrote in to
“scold” me for having suggested a
three-channel RC transmitter to a
beginner. Admittedly, as you progress
to four-channel (“full house,” as we
call it: elevator, aileron, rudder, and
throttle control), the throttle control
will be on the left stick and is operated
with an up-and-down motion.
I guess some apologies are in order.
Just keep in mind that the threechannel
RC system will never become
obsolete. It is well suited for my RC
sailplanes, parking-lot flyers, and
indoor RC.
I’m getting into more advanced RC
systems at this time because eventually
you will want to, and when you do you
will quickly appreciate some of the
extra features they can offer. You will
also be pleased to know that many of
these advanced radios are simple to
operate and are comparatively
inexpensive. So let’s get into it.
A basic RC transmitter, be it a threeor
four-channel-function unit, will not
be what we call a “computer” or
microprocessor-type radio. It will not
have a Liquid Crystal Display (LCD)
screen that allows you to set the
special commands or controls.
Most basic transmitters have servo
reversing, and a few might even offer
dual rate control on two-channel
functions. Servo direction is usually
changed with the flip of a tiny switch
(unplugging and rotating a cable on the
Hitec Neon). Dual rate control cutback
is adjusted by rotating a small
potentiometer control (dial). These
basic radios have a few switches and
potentiometers (dials) but no internal
computer circuitry and certainly no
New Airtronics VG6000A is popular
entry-level computer RC transmitter. It
will be featured in an MA product
review in the future.
02sig2.QXD 11/25/03 12:59 pm Page 46
memory circuits.
An advanced RC transmitter has an
internal computer chip that contains a
great deal of stored program information
in its memory circuits. It can also store
your control inputs, allowing you to
operate several models from a single
transmitter.
You can tell that it is a computer-driven
system because it has an LCD screen on
the front of the transmitter case. (One
exception is the FMA Direct T-80RF,
which is just a small step up from a basic
unit). The LCD screen displays a variety
of parameters; some are basic and
preplanned for you, and others you can
call up from a menu system that is
programmed into the transmitter.
How you access these menus, make
changes, and store the new inputs in the
memory is what an advanced RC
transmitter is all about. Once learned, you
February 2004 47
RC Systems
Typical RC transmitters (L-R): Hitec Neon three-channel (single
control stick); Hitec Laser 6, which has two control-stick
assemblies but is basic—not a computer radio; Futaba T6EXA
entry-level computer radio; Hitec Laser 6, which is computer
driven and has channel synthesizer.
L-R: Futaba T6EXA computer transmitter is covered in text. Hitec
Eclipse transmitter can be set for high or low FM deviation and
with Spectra synthesized module can dial up any of 50 RC
channels for models. Polk’s Tracker II has all Eclipse features,
but you don’t have to remove module to change channels.
Left: Rear of Hitec Neon three-channel single-stick transmitter.
Pointer shows location of throttle-control lever which must be
moved side to side to adjust engine/motor speeds. Right: Futaba
T6EXA computer transmitter, which has two control-stick
assemblies. Throttle control is obtained from left stick and
operated in up-and-down movement (for high and low throttle
settings).
Futaba T6EXA is roughly $180 from Tower
Hobbies. Full system has receiver, four
servos, full Ni-Cd battery packs.
by Bob Aberle
The JR XP662 distributed by Horizon Hobby is a popular entrylevel
Radio Control computer transmitter.
Photos courtesy the author
d
02sig2.QXD 11/25/03 12:59 pm Page 47
will have many more control features available for your use. You
can start with an advanced RC transmitter, but use only basic
controls until you gain a certain amount of experience.
Before I get into a computer-driven RC transmitter’s inner
workings, I must mention several more facts. Most modern RC
systems broadcast their signal on frequency modulation (FM).
Only a few amplitude modulation (AM) radio systems are still on
the market, and they are gradually disappearing.
You can’t intermix signals with these systems. An FM RC
transmitter can’t operate an AM RC receiver. Even within the FM
category, there are two types of signals that various manufacturers
employ. One is called FM deviation on the “low side.” Futaba,
Hitec RCD, FMA Direct, and GWS make use of this type of
signal. There is also FM deviation on the “high side,” as exhibited
in radios that JR Remote Control and Airtronics manufacture.
Keeping all of this in mind, a Futaba FM RC transmitter can
operate a Futaba FM RC receiver and FM RC receivers made by
Hitec, FMA Direct, and GWS. A JR FM RC transmitter can
operate a JR FM receiver and an Airtronics FM receiver.
Utilizing smart programming techniques, several RC
transmitters are able to select “high” or “low” FM deviation. This
can be a bonus since one transmitter can be used to operate almost
any brand of RC FM receiver on the hobby market, provided it is
on the same frequency (RC channel). Later I will mention an even
more sophisticated RC transmitter that uses a synthesizer which is
capable of dialing up any of the 50 RC channels available for
model aircraft.
I hate to get complicated early on, but in FM RC equipment
there is one other type known as pulse code modulation (PCM). It
is a technique in which a special digital code is added to the FM
signal. It provides much greater interference rejection than regular
FM, but it is usually only offered on the expensive, top-of-the-line
radio systems. These PCM systems also provide a fail-safe feature
that adjusts the controls to preset positions and reduces the engine
throttle if interference is experienced.
You should also know that each manufacturer uses its own
dedicated digital code, so you must stay with one brand for the
transmitter and receiver; you can’t intermix these units.
Types of Advanced RC Systems: You have already been
introduced to the basic radio. There are also “first step” computerdriven
RC transmitters. These entry-level systems offer many
extra control features, are relatively easy to use, and are
comparatively inexpensive (full systems range from $180 to
$250).
Several manufacturers offer a further step into the computerradio
market with systems ranging from $300 to $500. These offer
more features than the first-echelon systems but add a certain
amount of complexity. For the all-out expert competition-minded
pilot, there are top-of-the line radio systems that cost as much as
$1,000 and more. That won’t be for you for some time yet!
The First-Step Computer-Radio System: All of the popular RC
manufacturers—including Airtronics, FMA Direct, Futaba
(Hobbico), Hitec RCD/Multiplex, and JR (Horizon Hobby)—have
these entry-level computer-radio systems. Some of the big mailorder
hobby companies also offer “house radios,” but they are
generally made by the manufacturers I just listed.
The model numbers of these first-step radios are important for
identification purposes. For instance, the Airtronics VG6000 has a
new, innovative menu system. I expect to review this radio in
Model Aviation in the near future.
The Futaba T6EXA is simple and affordable (roughly $180!),
and this is the one I will explain in depth in a moment. Also
popular are the Hitec RCD Flash 5 X and Eclipse models and the
JR XP662. I have to admit that at this time I have little experience
with the new Hitec/Mulitplex systems from Europe.
You do not need to use any of the special features on these
first-level computer radios right away. You can turn off or inhibit
the extras while you learn to fly your first few RC models.
Futaba T6EXA: The heart of any computer-radio system is the
transmitter, and that is what I will discuss. Refer to the photos as I
proceed. Some photos are of the LCD screen on the T6EXA
transmitter, and others are of the illustrations in the Futaba
instruction manual (for added clarity).
Most RC-system manufacturers include their instruction
manuals on their Web sites. They are posted as PDFs (Portable
Document Formats) for viewing, or even printing, purposes. You
can access the Futaba T6EXA manual at www.futabarc.
com/manuals/6exa-manual.pdf.
The six-channel-control-function Futaba T6EXA transmitter
offers:
• low-voltage alarm
• digital trims
• six model memory positions
• the ability to reset any memory slot to the factory-default
positions
48 MODEL AVIATION
Upper left portion of Futaba T6EXA transmitter case. Switch on front
is for “CH.5 GEAR”—a nonproportional auxiliary channel. At top left
corner is “TRAINER/THT CUT”: a momentary contact switch you
pull forward to operate; when you let go, it springs back rearward. It
operates trainer cable function or can kill a glow-fueled engine.
Top right corner of transmitter case. “AIL/ELEV D/R” switch
turns dual rate, exponential rate control on or off. On top is
“CH.6 FLAPS” knob you turn to operate proportional sixth
channel function. You can use it to operate flaps, spoilers, or any
other auxiliary function.
02sig2.QXD 11/25/03 1:00 pm Page 48
Lower front part of Futaba T6EXA has LCD screen, control
necessary to operate built-in computer system. To left of screen
are “MODE,” “SELECT” switches. At right is “DATA INPUT”
switch; it rocks up or down for + or – control inputs. Each
channel function (six total) is listed next to DATA INPUT switch.
To enter menu system, turn on power then press and hold down
MODE and SELECT switches for roughly two seconds. “MODEL”
memory position (1 through 6) is first item to come up and will
flash. Press DATA INPUT switch to scroll around six positions.
This is how you select correct position to operate each model.
If you press SELECT while in MODEL portion of menu, letters
“CL” will flash on screen. Press DATA INPUT switch in either
direction (+ or –) and hold for a second to erase all control inputs
to this position and restore them to factory settings. This is
especially helpful when setting controls for new model.
This is the typical screen for reversing the servo direction for any
of the six channel functions.
When you initially turn on transmitter, basic screen display will
appear. Small “1” in upper right corner is current model-memory
position. Larger “8.5v” is transmitter battery voltage. At 8.5 volts,
audible alarm will sound and battery icon on screen will flash,
telling you to stop flying and recharge battery.
Since you can’t name models on LCD screen, Bob pastes list to
rear of transmitter. You could also put a note on your model,
such as “Futaba T6EXZ, No. 1”. That way you would be alerted to
take correct transmitter to field and make sure it is set on model
memory position 1.
February 2004 49
02sig2.QXD 11/25/03 1:01 pm Page 49
• dual rate control of two channel functions
• exponential rate control of two channels
• endpoint adjustment (EPA) on all channels
• servo reversing on all channels
• trim memory and position
• programmable mixing of any two channel functions
• wing mixing (elevons, flaperons, V-tail)
• throttle cut for glow-engine operation and provision for trainer
cable
It’s all there in that one transmitter case! Keep in mind that six
memory positions means that you can fly as many as six models
from this transmitter.
Looking at the T6EXA’s front panel, you will see the two dual
axis control-stick assemblies. When flying with only three
channels, the right stick operates the rudder and elevator and the
left stick moves up and down for the throttle control. All control
sticks have spring return to the neutral position except the throttle,
which has a ratchet device to hold the last position.
When using four-channel control, the right stick usually has
the aileron and elevator functions and the left stick assembly
provides rudder and throttle. For years this stick configuration has
been called Mode 2. A few pilots (mostly in Europe) still fly what
is called Mode 1. I have no intention of getting into that other
mode at this time, but the T6EXA is capable of Mode 1 control as
explained in the manual if that is your preference.
In addition to the four basic flight controls, a fifth channel is
available to operate a retractable landing gear, as a towhook
release on a sailplane, or as any other auxiliary function you
might think of. It is not a proportional control channel; the servo
goes to one side or the other (no neutral position). The fifth
channel is operated by the “CH.5 GEAR” switch at the upper left
corner of the case.
At the top right corner of the transmitter case is a knob that
proportionally operates a sixth channel function; it is identified as
“CH.6 FLAPS.” This channel is primarily used as a flap or spoiler
control, but, again, you could use it for a variety of auxiliary
functions.
There are several more switches on the front panel. At the
upper right is one identified as “AIL/ELEV D/R.” It
simultaneously turns on or off dual rate control for the
aileron/elevator (or rudder/elevator for three-channel control).
This switch also turns on/off the special exponential rate control
to the same two channel functions.
At the top left corner of the case is a momentary contact
(spring return) switch to operate the trainer-cable function. The
“From the Ground Up” installment in the September 2003 issue
(on page 71) has a more detailed discussion about using a trainer
cable.
When momentarily pulled forward and released, that trainercable
switch will act as an engine-kill (stop) switch. This is
helpful when your transmitter employs digital trim, as does the
T6EXA. By pulling this switch, you don’t have to operate the
throttle digital trim lever to completely kill your glow-fueled
engine. (Frank Granelli will explain this in more depth later in
this series.)
We’ve finally gotten to the computer system. At the lower
50 MODEL AVIATION
Dual rate control allows you to reduce amount of control throw
from 100% to 0%. Then by throwing D/R switch on front panel,
you can obtain reduced control throw in flight. Dual rate control
is only available on CH1 (aileron or rudder) and CH2 (elevator).
While in dual rate menu, if you press SELECT beyond CH2 you
will come to exponential rate control. You will see =/– sign
followed by 0%. As you reduce percentage in negative direction
(“–5,” “–10,” “–15,” etc.), controls react slower around neutral
position, giving “softer” feel in flight. This feature is also available
on CH1 and CH2 and can be combined with dual rate control.
EPA (endpoint adjustment) is probably the transmitter’s most
worthwhile feature and will be popular even with a rank beginner.
It lets you adjust control throw of any servo, and it will let you do
that independently. You can set more up- than down-elevator!
02sig2.QXD 11/25/03 1:01 pm Page 50
portion (middle) of the transmitter case is
an LCD screen. To the left of the screen
are two push-button switches identified as
“MODE” and “SELECT.” To the right is a
data-input switch that moves up (+) and
down (–). Next to this switch the six
channel controls are listed by number and
function, such as “CH1=Aileron,”
“CH2=Elevator,” etc.
When you first turn on the transmitter
power, an initial or basic display will
appear on the LCD screen. It will have a
small number (1 through 6) at the upper
right and a larger number, such as 10.0v, at
the lower right. The smaller number tells
you which computer-memory position is
currently in operation.
The larger number is this particular
transmitter’s battery voltage. At 10.0 volts
or slightly higher, the transmitter battery is
close to full charge. When the voltage falls
to 8.5, an audible alarm will sound and a
battery icon will flash on the LCD screen.
This is a warning to land your model
immediately because you only have
several minutes of charge remaining. At
that point you recharge the battery or
substitute a freshly charged battery pack.
To access the various control features,
you must get into the T6EXA computer
menu. Many of these computer radios have
two menus; one is for basic programming
and selection of the model memory and the
other contains all of the detailed control
features. I chose the T6EXA because it
only has one menu, which makes it simple.
With the transmitter power on, press
the MODE and SELECT switches (keys)
and hold them for a second or two. The
first thing to show up on the LCD screen is
the “MODEL” memory position. A largesize
number (1 through 6) will flash on the
screen. You change the model number by
pressing the data-input (+ or –) switch.
This will allow you to scroll up to 6 or
down to 1.
On some computer transmitters you can
add a model’s name to the memoryposition
number for identification
purposes, but that feature isn’t available on
this unit. As an alternative I pasted a list
on the rear of the case indicating each
model and the number assigned to it.
You must be especially careful when
selecting the correct model-memory
position. If you don’t select the right
number, you may find your controls
reversed and a crash could easily result.
On the other hand, remember that you can
operate as many as six different aircraft
from this transmitter.
While still in the MODEL portion of
the menu, if you press SELECT you will
see a “CL” flash on the LCD screen along
with the model memory-position number.
Pressing either data-input key (+ or –) for
February 2004 51
This is how EPA function looks when called up on LCD screen.
You can select CH1 or CH2, then amount of control-throw
reduction (from 100% to 0%—which you won’t be doing!).
Amount of trim used on any of four main channel functions can
be displayed in this part of menu. Any trim you set in flight is
automatically saved until you change it on later flight. While in
this portion of menu, you can add or subtract trim by following
numerical position displayed on LCD screen.
P.MIX allows you to mix any two channel functions. You could
have small amount of rudder control when applying aileron to
smooth out or coordinate turns. “Inh” indicates that P.MIX is
turned off or inhibited.
W.MIX lets you set up programmed mixing for elevon control,
flaperons, or V-tail operation (as explained in text).
02sig2.QXD 11/25/03 1:01 pm Page 51
52 MODEL AVIATION
roughly two seconds will erase any inputs
stored in that memory position. Controls
will then be restored to factory-default
settings. This can be helpful when you are
setting up controls for a new model.
Moving along the menu, press MODE
and you come to “REVERSE.” This
function will let you reverse any servo’s
direction. Press SELECT to choose the
channel function you want to reverse (1 to
6), and then press + or – to select the
“NOR” (normal) or “REV” (reverse) servo
direction. Press MODE again, and the
“D/R” (Dual Rate) function comes up. The
menu keeps going in one direction, as in a
loop. If you miss an item, keep pressing
MODE until it appears again.
Dual rate control applies only to
channels 1 (aileron or rudder when flying
with three channels) and 2 (elevator). The
LCD screen will show CH 1 or CH 2,
which you choose by pressing SELECT.
Then you will see 100%, meaning that the
control is set for “full,” or maximum
throw. Use the data-input – switch to
reduce the control to something less than
full.
Now that AIL/ELEV D/R switch at the
upper right comes into play. With it in the
down position, you want your aileron or
rudder and your elevator at full throw, or
100%. Move that switch to the upper
position, and the reduced throw that you
just set (something less than 100%) will
appear. Keep in mind that the AIL/ELEV
D/R switch affects the two channels at the
same time on this transmitter; you can’t
separate the aileron and elevator functions.
Dual rate control can be helpful on
faster models. At takeoff and landing
speeds you have the controls set at full, or
100%. During the flight, you can flip the
D/R switch to the up position and the
controls will be reduced somewhat,
making the airplane easier to fly at high
speeds.
When pressing the SELECT switch
while in this same D/R function, after D/R
you will come to an added feature called
exponential rate control. When you get to
this function you will see a plus and minus
sign and 0% on the LCD screen. If you
then press the minus switch, you will see a
negative number such as 5, 8, 10, 15, etc.
These negative numbers make the initial
servo movement less than normal.
What happens is that the control
response is slower or “softer” around the
neutral position. By selecting that negative
number, you can tailor the feel to suit you
and your model. I realize that this sounds
slightly complicated at first, but you will
learn as you gain experience with the
system. Keep in mind that with the
T6EXA you can have dual rate and
exponential rate together or you can have
dual rate or exponential rate separately.
The next menu item (press MODE) is
EPA. This is available on all six channels.
It is especially nice to have EPA on the
throttle channel when using a fueled
engine; it makes high and low carburetor
adjustments so easy.
With EPA you can set the servo control
throw to the exact amount of control
required. You can even set the elevator for
more up than down or more right aileron
than left. This is probably the best feature
in a computer-radio system. It is the
control function you will use the most.
As you go through the menu and make
control adjustments, your inputs are saved
automatically in the computer each time
you move on to the next menu item or if
you turn the power off. Afterward, any
time you call up that particular model
memory position, the control inputs you
made will be right there for you (stored in
the computer memory).
The next menu item is important
because it involves the trim function. Each
of the four main channels has a separate
trim switch. On this transmitter the trim is
the more modern digital variety. The
purpose of trim is to allow you to set your
model for straight and level flight with
your hands off of the control sticks. You
“rocker” the trim switches left or right or
up and down to achieve level flight
characteristics.
Once you have a model adjusted for
level flight, you can call up the “TRIM”
menu item. It will allow you to select any
one of the four channels that provide trim
(aileron, elevator, rudder, or throttle). For
02sig2.QXD 11/25/03 1:01 pm Page 52
Transmitter’s battery-compartment cover has been removed and
battery pack (red case) partially removed. Battery has only 600 mAh
capacity—enough to operate transmitter for roughly two hours.
You could substitute packs with almost double the capacity that
still fit in compartment. If you go to higher capacity, you will have to
buy variable output charger such as ACE R/C DDVC shown.
These are some RC-system connectors with which you may
come in contact. At top is transmitter charging jack. In middle are
mating halves of receiver battery cables (only two wires
employed). At bottom is servo connector with three wires.
Convention today throughout hobby industry is to have negative
pin in middle. If servo connector is plugged in backward (hard to
do!), servo will not work but will not be damaged.
To show you that Bob also thinks about receivers, at top is his
first, from 1953—the Miller—which was featured in MAN that
year. It weighed 5 ounces and offered only single-channel control
of rudder. In middle are typical, current Futaba and Airtronics
dual-conversion RC FM receivers. At bottom right is FMA Direct
aftermarket receiver. At bottom left is popular 0.2-ounce GWS
R4P micro four-channel receiver.
Spectra synthesized module removed from Hitec Eclipse
transmitter. By rotating two dials shown, you can obtain any of
50 channels available for model use on 72 MHz band.
Polk’s Modelcraft Hobbies’ new Tracker II transmitter, companion
Seeker receiver. Transmitter is synthesized to operate on all 50
channels. Scanning receiver inside transmitter listens to see if
channel you chose is clear before it allows it to be turned on.
Seeker can automatically lock onto any channel set on Tracker II.
Tracker II’s LCD screen shows memory position 2, that channel
is set at 52, and exact frequency of that channel. “10.01V” is
transmitter voltage.
February 2004 53
02sig2.QXD 11/25/03 1:04 pm Page 53
each function the LCD screen will provide
a numerical trim position. This is strictly
for reference purposes. Remember that
whatever trim you use on a particular
model to achieve level flight will be stored
in the computer and will remain until you
make changes.
On this particular transmitter, the fifth
and sixth channel functions do not have
trim. Also, on the CH 3 throttle function
the trim only operates when the control
stick is down close to minimum throttle.
This is so you can set your fueled engine
carburetor for the lowest possible idle
speed yet not stall the engine. Frank
Granelli will go into this feature.
The remaining menu items cover
certain mixing functions. There is a
programmable mixing (“P.MIX”) circuit
that will let you combine any two control
functions. I like to use this for coupled
aileron and rudder on some models. When
you apply ailerons to bank the model, the
rudder will respond to that single
command.
Several wing-mix (“W.MIX”) functions
can provide such things as elevon control
(“EL”) that will mix aileron and elevator
for flying wings or delta-wing models. The
flaperon (“FP”) function makes both
ailerons drop down for flap-type control. A
V-tail (“V”) mixing function provides a
rudder and elevator effect, as on a Scale
Beechcraft Bonanza. I won’t get into these
mixer functions in any detail because you
probably won’t be using them right away.
Quite a few computer-driven RC
transmitters include multimodel-type
programming; they offer menus
specifically for fixed-wing aircraft, for
helicopters, and in some cases for
sailplanes. This makes for some difficult
menu searching. Also, the switches are
marked three ways, making identification
difficult. I chose the T6EXA radio because
it has one menu and is intended
exclusively for fixed-wing aircraft.
Many of these computer RC
transmitters draw upward of 200 mA of
current. It is still common to see 600 mAhcapacity
Ni-Cd batteries supplied with
these systems, but in today’s hobby market
we are seeing NiMH batteries in the same
AA size with capacities up to 1100 mAh
and more.
Batteries such as these are available
from suppliers such as Batteries America
and SR Batteries. They even provide the
mating connectors for your particular
brand of transmitter. If you want more
capacity with which to operate your
transmitter for longer periods of time,
these higher-capacity replacement packs
are the way to go.
Just remember from my “Battery
Basics” article (in the October 2003 Model
Aviation) that you must charge these
batteries at the rate of C/10 (capacity
divided by 10). An 1100 mAh battery
would have to be charged overnight at 110
mA. To obtain that kind of current you
will need a variable output charger, such
as the Ace R/C Digital Dual Variable
Charger.
A number of computer transmitters
currently on the market employ a
synthesizer: a circuit that allows you to
dial up any one of the 50 channels
available for flying model aircraft. You
can purchase the Hitec Eclipse transmitter
with Hitec’s Spectra synthesized module.
This module plugs into the rear of the
transmitter case. To change channels, you
unplug the module and rotate two tiny
dials to obtain any channel from 11 to 60.
The Eclipse is also one of the
transmitters that lets you select high or low
FM deviation. That means you can operate
any FM RC receiver on the market with
this transmitter (regardless of the deviation
or the channel number).
Polk’s Modelcraft Hobbies has gone
one better with its Tracker II computerdriven
transmitter, which accommodates
more than 90 memory positions. A
synthesizer lets you select any one of the
50 RC aircraft channels using the LCD
screen so you don’t have to remove a
module and twist any dials. You can also
enter the channel number for each model
into the memory along with the proper
deviation.
When you first turn on the Tracker, a
built-in scanning receiver (right inside the
54 MODEL AVIATION
02sig2.QXD 11/25/03 1:04 pm Page 54
transmitter) scans the operating channel
before allowing it to go on the air. The
Polk’s Seeker companion receiver can
listen for an FM signal and then set itself
to that channel. With this concept you
could switch channels every flight and
never have to wait for an available
channel.
The fact that these computer-driven
transmitters can store control data for
many models means that you will need
many more receivers (one for each model)
but only one transmitter. Generally, the
RC manufacturers would like to sell you
an entire system: transmitter, receiver, and
servos. Through the years, many of these
manufacturers have priced airborne packs
(receiver and servos) at practically what it
costs for a full system.
More recently, companies have come
out expressly with aftermarket receivers
and servos that will work from almost any
computer-driven transmitter. FMA Direct
has a complete line of receivers and
servos. It even has a micro-size dualconversion
receiver (the M5) that weighs
0.35 ounce! Using aftermarket
microreceivers and microservos is
commonplace today, especially with
parking-lot and indoor RC flyers.
When mixing and matching computer
transmitters, receivers, and servos, you
will have to contend, to a degree, with
connector polarity. Connectors used on
receivers, switch harnesses, and servos
now follow the same convention.
On three-pin servo connectors, one
outside pin is battery negative, the center
pin is battery positive, and the other
outside pin is the signal. Plug it in one
way, and the servo works. Reverse the
connector (some have keys that prevent
this possibility), and the servo does not
work.
One thing is for sure: you cannot blow
out that servo with this type of polarity
convention. Years ago this was much
more of a problem. The only connector
that is still different is the charger plug on
the JR transmitters; the center pin and
outside connection are different on this
plug than on all others in the RC hobby
industry.
For the More Advanced RC Pilot: Most
of us fly on one of the 50 RC channels that
the Federal Communications Commission
(FCC) has made available expressly for
the control of model aircraft. With 50
channels to choose from and added
features such as synthesizers with dial-up
channel-selection capabilities, you never
have to wait very long to make a flight.
However, you may see certain
concentrations of channels at local flying
fields. One possibility to avoid a “channel
traffic jam” is to obtain an FCC ham radio
license and then operate on the Amateur
Radio Service 6-meter band (50 MHz).
Many RC manufacturers offer systems on
10 channels near 50 MHz.
If you are interested in what it takes to
become a ham and practically be able to
fly on your own channel, contact the
national organization (which is like our
AMA). It is the American Radio Relay
League, 225 Main St., Newington CT
06111; Tel.: (880) 594-0200; Web site:
www.arrl.org.
My articles in this series began with the
March 2003 Model Aviation. Look for
Frank Granelli and the glow-fueled-model
input for months to come. I expect to do
several “guest spots” on subjects such as
parking-lot/backyard flying, indoor RC,
Lithium-Polymer batteries and their
application, and some FAQs (frequently-
56 MODEL AVIATION
asked questions), which will be published
next month.
Keep in mind that this series is posted on
the Model Aviation portion of the AMA’s
Web site, at http://modelaircraft.org/mag/
index.htm. MA
Bob Aberle
Manufacturers:
Ace Hobby Distributors, Inc.
2055 Main St.
Irvine CA 92614
(949) 833-0088
Fax: (949) 833-0003
www.acehobby.com
Airtronics Inc.
1185 Stanford Ct.
Anaheim CA 92805
(714) 978-1895
[email protected]
www.airtronics.net
Batteries America
2211-D Parview Rd.
Middleton WI 53562
(800) 308-4805
[email protected]
www.batteriesamerica.com
FMA Direct
5716A Industry Ln.
Frederick MD 21704
(800) 343-2934
Fax: (301) 668-7619
[email protected]
www.fmadirect.com
GWS (also sold by Horizon Hobby)
Balsa Products
22 Jansen Ave.
Iselin NJ 08830
(732) 634-6131
www.balsapr.com
Hitec RCD (and Multiplex)
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
www.horizonhobby.com
SR Batteries Inc.
Box 287
Bellport NY 11713
(631) 286-0079
Fax: (631) 286-0901
[email protected]
www.srbatteries.com
Tower Hobbies (Hobbico and Futaba
radios)
Box 9078
Champaign IL 61826
(800) 637-6050
www.towerhobbies.com
02sig2.QXD 11/25/03 1:05 pm Page 56

46 MODEL AVIATION
Advanced
THIS IS MY 10TH
installment in this initial
phase of the “From the
Ground Up” series. I’ll
be back next month with
some frequently-asked
questions and in the
April issue the emphasis
will shift to fueled models under Frank
Granelli’s expert tutelage.
At the beginning of this series I
discussed some of the basic Radio
Control (RC) systems as an overall
introduction to the model-aircraft
hobby. To keep it simple and
inexpensive, I selected a basic threechannel
transmitter with a single
control stick. I use several of these
systems for my flying, so please don’t
worry; I didn’t recommend that you
buy something that would quickly
become obsolete.
As the series progressed I described
the Hitec Neon three-channel system,
then the electric power system, and
then the Aero Craft Pogo as a firsttime
(Almost Ready-to-Fly) training
aircraft.
My student Jay Federman had
already done a bit of flying on his
own, and he owned a four-channel,
dual-stick RC transmitter. When we
flew the Pogo for the first time, using a
trainer cable, Jay had to hold the Neon
transmitter since it was the one
broadcasting the signal. The master
control was my transmitter (a dualstick-
assembly four-channel unit),
which I held as the instructor pilot.
Jay got confused because the
throttle lever is on the rear of the case
(of the three-channel transmitter) and
it operates with a side-to-side motion.
He had done some flying using a leftside
control stick that moved up for
high speed and down for idle speeds.
I recognized this problem right
away, and many readers wrote in to
“scold” me for having suggested a
three-channel RC transmitter to a
beginner. Admittedly, as you progress
to four-channel (“full house,” as we
call it: elevator, aileron, rudder, and
throttle control), the throttle control
will be on the left stick and is operated
with an up-and-down motion.
I guess some apologies are in order.
Just keep in mind that the threechannel
RC system will never become
obsolete. It is well suited for my RC
sailplanes, parking-lot flyers, and
indoor RC.
I’m getting into more advanced RC
systems at this time because eventually
you will want to, and when you do you
will quickly appreciate some of the
extra features they can offer. You will
also be pleased to know that many of
these advanced radios are simple to
operate and are comparatively
inexpensive. So let’s get into it.
A basic RC transmitter, be it a threeor
four-channel-function unit, will not
be what we call a “computer” or
microprocessor-type radio. It will not
have a Liquid Crystal Display (LCD)
screen that allows you to set the
special commands or controls.
Most basic transmitters have servo
reversing, and a few might even offer
dual rate control on two-channel
functions. Servo direction is usually
changed with the flip of a tiny switch
(unplugging and rotating a cable on the
Hitec Neon). Dual rate control cutback
is adjusted by rotating a small
potentiometer control (dial). These
basic radios have a few switches and
potentiometers (dials) but no internal
computer circuitry and certainly no
New Airtronics VG6000A is popular
entry-level computer RC transmitter. It
will be featured in an MA product
review in the future.
02sig2.QXD 11/25/03 12:59 pm Page 46
memory circuits.
An advanced RC transmitter has an
internal computer chip that contains a
great deal of stored program information
in its memory circuits. It can also store
your control inputs, allowing you to
operate several models from a single
transmitter.
You can tell that it is a computer-driven
system because it has an LCD screen on
the front of the transmitter case. (One
exception is the FMA Direct T-80RF,
which is just a small step up from a basic
unit). The LCD screen displays a variety
of parameters; some are basic and
preplanned for you, and others you can
call up from a menu system that is
programmed into the transmitter.
How you access these menus, make
changes, and store the new inputs in the
memory is what an advanced RC
transmitter is all about. Once learned, you
February 2004 47
RC Systems
Typical RC transmitters (L-R): Hitec Neon three-channel (single
control stick); Hitec Laser 6, which has two control-stick
assemblies but is basic—not a computer radio; Futaba T6EXA
entry-level computer radio; Hitec Laser 6, which is computer
driven and has channel synthesizer.
L-R: Futaba T6EXA computer transmitter is covered in text. Hitec
Eclipse transmitter can be set for high or low FM deviation and
with Spectra synthesized module can dial up any of 50 RC
channels for models. Polk’s Tracker II has all Eclipse features,
but you don’t have to remove module to change channels.
Left: Rear of Hitec Neon three-channel single-stick transmitter.
Pointer shows location of throttle-control lever which must be
moved side to side to adjust engine/motor speeds. Right: Futaba
T6EXA computer transmitter, which has two control-stick
assemblies. Throttle control is obtained from left stick and
operated in up-and-down movement (for high and low throttle
settings).
Futaba T6EXA is roughly $180 from Tower
Hobbies. Full system has receiver, four
servos, full Ni-Cd battery packs.
by Bob Aberle
The JR XP662 distributed by Horizon Hobby is a popular entrylevel
Radio Control computer transmitter.
Photos courtesy the author
d
02sig2.QXD 11/25/03 12:59 pm Page 47
will have many more control features available for your use. You
can start with an advanced RC transmitter, but use only basic
controls until you gain a certain amount of experience.
Before I get into a computer-driven RC transmitter’s inner
workings, I must mention several more facts. Most modern RC
systems broadcast their signal on frequency modulation (FM).
Only a few amplitude modulation (AM) radio systems are still on
the market, and they are gradually disappearing.
You can’t intermix signals with these systems. An FM RC
transmitter can’t operate an AM RC receiver. Even within the FM
category, there are two types of signals that various manufacturers
employ. One is called FM deviation on the “low side.” Futaba,
Hitec RCD, FMA Direct, and GWS make use of this type of
signal. There is also FM deviation on the “high side,” as exhibited
in radios that JR Remote Control and Airtronics manufacture.
Keeping all of this in mind, a Futaba FM RC transmitter can
operate a Futaba FM RC receiver and FM RC receivers made by
Hitec, FMA Direct, and GWS. A JR FM RC transmitter can
operate a JR FM receiver and an Airtronics FM receiver.
Utilizing smart programming techniques, several RC
transmitters are able to select “high” or “low” FM deviation. This
can be a bonus since one transmitter can be used to operate almost
any brand of RC FM receiver on the hobby market, provided it is
on the same frequency (RC channel). Later I will mention an even
more sophisticated RC transmitter that uses a synthesizer which is
capable of dialing up any of the 50 RC channels available for
model aircraft.
I hate to get complicated early on, but in FM RC equipment
there is one other type known as pulse code modulation (PCM). It
is a technique in which a special digital code is added to the FM
signal. It provides much greater interference rejection than regular
FM, but it is usually only offered on the expensive, top-of-the-line
radio systems. These PCM systems also provide a fail-safe feature
that adjusts the controls to preset positions and reduces the engine
throttle if interference is experienced.
You should also know that each manufacturer uses its own
dedicated digital code, so you must stay with one brand for the
transmitter and receiver; you can’t intermix these units.
Types of Advanced RC Systems: You have already been
introduced to the basic radio. There are also “first step” computerdriven
RC transmitters. These entry-level systems offer many
extra control features, are relatively easy to use, and are
comparatively inexpensive (full systems range from $180 to
$250).
Several manufacturers offer a further step into the computerradio
market with systems ranging from $300 to $500. These offer
more features than the first-echelon systems but add a certain
amount of complexity. For the all-out expert competition-minded
pilot, there are top-of-the line radio systems that cost as much as
$1,000 and more. That won’t be for you for some time yet!
The First-Step Computer-Radio System: All of the popular RC
manufacturers—including Airtronics, FMA Direct, Futaba
(Hobbico), Hitec RCD/Multiplex, and JR (Horizon Hobby)—have
these entry-level computer-radio systems. Some of the big mailorder
hobby companies also offer “house radios,” but they are
generally made by the manufacturers I just listed.
The model numbers of these first-step radios are important for
identification purposes. For instance, the Airtronics VG6000 has a
new, innovative menu system. I expect to review this radio in
Model Aviation in the near future.
The Futaba T6EXA is simple and affordable (roughly $180!),
and this is the one I will explain in depth in a moment. Also
popular are the Hitec RCD Flash 5 X and Eclipse models and the
JR XP662. I have to admit that at this time I have little experience
with the new Hitec/Mulitplex systems from Europe.
You do not need to use any of the special features on these
first-level computer radios right away. You can turn off or inhibit
the extras while you learn to fly your first few RC models.
Futaba T6EXA: The heart of any computer-radio system is the
transmitter, and that is what I will discuss. Refer to the photos as I
proceed. Some photos are of the LCD screen on the T6EXA
transmitter, and others are of the illustrations in the Futaba
instruction manual (for added clarity).
Most RC-system manufacturers include their instruction
manuals on their Web sites. They are posted as PDFs (Portable
Document Formats) for viewing, or even printing, purposes. You
can access the Futaba T6EXA manual at www.futabarc.
com/manuals/6exa-manual.pdf.
The six-channel-control-function Futaba T6EXA transmitter
offers:
• low-voltage alarm
• digital trims
• six model memory positions
• the ability to reset any memory slot to the factory-default
positions
48 MODEL AVIATION
Upper left portion of Futaba T6EXA transmitter case. Switch on front
is for “CH.5 GEAR”—a nonproportional auxiliary channel. At top left
corner is “TRAINER/THT CUT”: a momentary contact switch you
pull forward to operate; when you let go, it springs back rearward. It
operates trainer cable function or can kill a glow-fueled engine.
Top right corner of transmitter case. “AIL/ELEV D/R” switch
turns dual rate, exponential rate control on or off. On top is
“CH.6 FLAPS” knob you turn to operate proportional sixth
channel function. You can use it to operate flaps, spoilers, or any
other auxiliary function.
02sig2.QXD 11/25/03 1:00 pm Page 48
Lower front part of Futaba T6EXA has LCD screen, control
necessary to operate built-in computer system. To left of screen
are “MODE,” “SELECT” switches. At right is “DATA INPUT”
switch; it rocks up or down for + or – control inputs. Each
channel function (six total) is listed next to DATA INPUT switch.
To enter menu system, turn on power then press and hold down
MODE and SELECT switches for roughly two seconds. “MODEL”
memory position (1 through 6) is first item to come up and will
flash. Press DATA INPUT switch to scroll around six positions.
This is how you select correct position to operate each model.
If you press SELECT while in MODEL portion of menu, letters
“CL” will flash on screen. Press DATA INPUT switch in either
direction (+ or –) and hold for a second to erase all control inputs
to this position and restore them to factory settings. This is
especially helpful when setting controls for new model.
This is the typical screen for reversing the servo direction for any
of the six channel functions.
When you initially turn on transmitter, basic screen display will
appear. Small “1” in upper right corner is current model-memory
position. Larger “8.5v” is transmitter battery voltage. At 8.5 volts,
audible alarm will sound and battery icon on screen will flash,
telling you to stop flying and recharge battery.
Since you can’t name models on LCD screen, Bob pastes list to
rear of transmitter. You could also put a note on your model,
such as “Futaba T6EXZ, No. 1”. That way you would be alerted to
take correct transmitter to field and make sure it is set on model
memory position 1.
February 2004 49
02sig2.QXD 11/25/03 1:01 pm Page 49
• dual rate control of two channel functions
• exponential rate control of two channels
• endpoint adjustment (EPA) on all channels
• servo reversing on all channels
• trim memory and position
• programmable mixing of any two channel functions
• wing mixing (elevons, flaperons, V-tail)
• throttle cut for glow-engine operation and provision for trainer
cable
It’s all there in that one transmitter case! Keep in mind that six
memory positions means that you can fly as many as six models
from this transmitter.
Looking at the T6EXA’s front panel, you will see the two dual
axis control-stick assemblies. When flying with only three
channels, the right stick operates the rudder and elevator and the
left stick moves up and down for the throttle control. All control
sticks have spring return to the neutral position except the throttle,
which has a ratchet device to hold the last position.
When using four-channel control, the right stick usually has
the aileron and elevator functions and the left stick assembly
provides rudder and throttle. For years this stick configuration has
been called Mode 2. A few pilots (mostly in Europe) still fly what
is called Mode 1. I have no intention of getting into that other
mode at this time, but the T6EXA is capable of Mode 1 control as
explained in the manual if that is your preference.
In addition to the four basic flight controls, a fifth channel is
available to operate a retractable landing gear, as a towhook
release on a sailplane, or as any other auxiliary function you
might think of. It is not a proportional control channel; the servo
goes to one side or the other (no neutral position). The fifth
channel is operated by the “CH.5 GEAR” switch at the upper left
corner of the case.
At the top right corner of the transmitter case is a knob that
proportionally operates a sixth channel function; it is identified as
“CH.6 FLAPS.” This channel is primarily used as a flap or spoiler
control, but, again, you could use it for a variety of auxiliary
functions.
There are several more switches on the front panel. At the
upper right is one identified as “AIL/ELEV D/R.” It
simultaneously turns on or off dual rate control for the
aileron/elevator (or rudder/elevator for three-channel control).
This switch also turns on/off the special exponential rate control
to the same two channel functions.
At the top left corner of the case is a momentary contact
(spring return) switch to operate the trainer-cable function. The
“From the Ground Up” installment in the September 2003 issue
(on page 71) has a more detailed discussion about using a trainer
cable.
When momentarily pulled forward and released, that trainercable
switch will act as an engine-kill (stop) switch. This is
helpful when your transmitter employs digital trim, as does the
T6EXA. By pulling this switch, you don’t have to operate the
throttle digital trim lever to completely kill your glow-fueled
engine. (Frank Granelli will explain this in more depth later in
this series.)
We’ve finally gotten to the computer system. At the lower
50 MODEL AVIATION
Dual rate control allows you to reduce amount of control throw
from 100% to 0%. Then by throwing D/R switch on front panel,
you can obtain reduced control throw in flight. Dual rate control
is only available on CH1 (aileron or rudder) and CH2 (elevator).
While in dual rate menu, if you press SELECT beyond CH2 you
will come to exponential rate control. You will see =/– sign
followed by 0%. As you reduce percentage in negative direction
(“–5,” “–10,” “–15,” etc.), controls react slower around neutral
position, giving “softer” feel in flight. This feature is also available
on CH1 and CH2 and can be combined with dual rate control.
EPA (endpoint adjustment) is probably the transmitter’s most
worthwhile feature and will be popular even with a rank beginner.
It lets you adjust control throw of any servo, and it will let you do
that independently. You can set more up- than down-elevator!
02sig2.QXD 11/25/03 1:01 pm Page 50
portion (middle) of the transmitter case is
an LCD screen. To the left of the screen
are two push-button switches identified as
“MODE” and “SELECT.” To the right is a
data-input switch that moves up (+) and
down (–). Next to this switch the six
channel controls are listed by number and
function, such as “CH1=Aileron,”
“CH2=Elevator,” etc.
When you first turn on the transmitter
power, an initial or basic display will
appear on the LCD screen. It will have a
small number (1 through 6) at the upper
right and a larger number, such as 10.0v, at
the lower right. The smaller number tells
you which computer-memory position is
currently in operation.
The larger number is this particular
transmitter’s battery voltage. At 10.0 volts
or slightly higher, the transmitter battery is
close to full charge. When the voltage falls
to 8.5, an audible alarm will sound and a
battery icon will flash on the LCD screen.
This is a warning to land your model
immediately because you only have
several minutes of charge remaining. At
that point you recharge the battery or
substitute a freshly charged battery pack.
To access the various control features,
you must get into the T6EXA computer
menu. Many of these computer radios have
two menus; one is for basic programming
and selection of the model memory and the
other contains all of the detailed control
features. I chose the T6EXA because it
only has one menu, which makes it simple.
With the transmitter power on, press
the MODE and SELECT switches (keys)
and hold them for a second or two. The
first thing to show up on the LCD screen is
the “MODEL” memory position. A largesize
number (1 through 6) will flash on the
screen. You change the model number by
pressing the data-input (+ or –) switch.
This will allow you to scroll up to 6 or
down to 1.
On some computer transmitters you can
add a model’s name to the memoryposition
number for identification
purposes, but that feature isn’t available on
this unit. As an alternative I pasted a list
on the rear of the case indicating each
model and the number assigned to it.
You must be especially careful when
selecting the correct model-memory
position. If you don’t select the right
number, you may find your controls
reversed and a crash could easily result.
On the other hand, remember that you can
operate as many as six different aircraft
from this transmitter.
While still in the MODEL portion of
the menu, if you press SELECT you will
see a “CL” flash on the LCD screen along
with the model memory-position number.
Pressing either data-input key (+ or –) for
February 2004 51
This is how EPA function looks when called up on LCD screen.
You can select CH1 or CH2, then amount of control-throw
reduction (from 100% to 0%—which you won’t be doing!).
Amount of trim used on any of four main channel functions can
be displayed in this part of menu. Any trim you set in flight is
automatically saved until you change it on later flight. While in
this portion of menu, you can add or subtract trim by following
numerical position displayed on LCD screen.
P.MIX allows you to mix any two channel functions. You could
have small amount of rudder control when applying aileron to
smooth out or coordinate turns. “Inh” indicates that P.MIX is
turned off or inhibited.
W.MIX lets you set up programmed mixing for elevon control,
flaperons, or V-tail operation (as explained in text).
02sig2.QXD 11/25/03 1:01 pm Page 51
52 MODEL AVIATION
roughly two seconds will erase any inputs
stored in that memory position. Controls
will then be restored to factory-default
settings. This can be helpful when you are
setting up controls for a new model.
Moving along the menu, press MODE
and you come to “REVERSE.” This
function will let you reverse any servo’s
direction. Press SELECT to choose the
channel function you want to reverse (1 to
6), and then press + or – to select the
“NOR” (normal) or “REV” (reverse) servo
direction. Press MODE again, and the
“D/R” (Dual Rate) function comes up. The
menu keeps going in one direction, as in a
loop. If you miss an item, keep pressing
MODE until it appears again.
Dual rate control applies only to
channels 1 (aileron or rudder when flying
with three channels) and 2 (elevator). The
LCD screen will show CH 1 or CH 2,
which you choose by pressing SELECT.
Then you will see 100%, meaning that the
control is set for “full,” or maximum
throw. Use the data-input – switch to
reduce the control to something less than
full.
Now that AIL/ELEV D/R switch at the
upper right comes into play. With it in the
down position, you want your aileron or
rudder and your elevator at full throw, or
100%. Move that switch to the upper
position, and the reduced throw that you
just set (something less than 100%) will
appear. Keep in mind that the AIL/ELEV
D/R switch affects the two channels at the
same time on this transmitter; you can’t
separate the aileron and elevator functions.
Dual rate control can be helpful on
faster models. At takeoff and landing
speeds you have the controls set at full, or
100%. During the flight, you can flip the
D/R switch to the up position and the
controls will be reduced somewhat,
making the airplane easier to fly at high
speeds.
When pressing the SELECT switch
while in this same D/R function, after D/R
you will come to an added feature called
exponential rate control. When you get to
this function you will see a plus and minus
sign and 0% on the LCD screen. If you
then press the minus switch, you will see a
negative number such as 5, 8, 10, 15, etc.
These negative numbers make the initial
servo movement less than normal.
What happens is that the control
response is slower or “softer” around the
neutral position. By selecting that negative
number, you can tailor the feel to suit you
and your model. I realize that this sounds
slightly complicated at first, but you will
learn as you gain experience with the
system. Keep in mind that with the
T6EXA you can have dual rate and
exponential rate together or you can have
dual rate or exponential rate separately.
The next menu item (press MODE) is
EPA. This is available on all six channels.
It is especially nice to have EPA on the
throttle channel when using a fueled
engine; it makes high and low carburetor
adjustments so easy.
With EPA you can set the servo control
throw to the exact amount of control
required. You can even set the elevator for
more up than down or more right aileron
than left. This is probably the best feature
in a computer-radio system. It is the
control function you will use the most.
As you go through the menu and make
control adjustments, your inputs are saved
automatically in the computer each time
you move on to the next menu item or if
you turn the power off. Afterward, any
time you call up that particular model
memory position, the control inputs you
made will be right there for you (stored in
the computer memory).
The next menu item is important
because it involves the trim function. Each
of the four main channels has a separate
trim switch. On this transmitter the trim is
the more modern digital variety. The
purpose of trim is to allow you to set your
model for straight and level flight with
your hands off of the control sticks. You
“rocker” the trim switches left or right or
up and down to achieve level flight
characteristics.
Once you have a model adjusted for
level flight, you can call up the “TRIM”
menu item. It will allow you to select any
one of the four channels that provide trim
(aileron, elevator, rudder, or throttle). For
02sig2.QXD 11/25/03 1:01 pm Page 52
Transmitter’s battery-compartment cover has been removed and
battery pack (red case) partially removed. Battery has only 600 mAh
capacity—enough to operate transmitter for roughly two hours.
You could substitute packs with almost double the capacity that
still fit in compartment. If you go to higher capacity, you will have to
buy variable output charger such as ACE R/C DDVC shown.
These are some RC-system connectors with which you may
come in contact. At top is transmitter charging jack. In middle are
mating halves of receiver battery cables (only two wires
employed). At bottom is servo connector with three wires.
Convention today throughout hobby industry is to have negative
pin in middle. If servo connector is plugged in backward (hard to
do!), servo will not work but will not be damaged.
To show you that Bob also thinks about receivers, at top is his
first, from 1953—the Miller—which was featured in MAN that
year. It weighed 5 ounces and offered only single-channel control
of rudder. In middle are typical, current Futaba and Airtronics
dual-conversion RC FM receivers. At bottom right is FMA Direct
aftermarket receiver. At bottom left is popular 0.2-ounce GWS
R4P micro four-channel receiver.
Spectra synthesized module removed from Hitec Eclipse
transmitter. By rotating two dials shown, you can obtain any of
50 channels available for model use on 72 MHz band.
Polk’s Modelcraft Hobbies’ new Tracker II transmitter, companion
Seeker receiver. Transmitter is synthesized to operate on all 50
channels. Scanning receiver inside transmitter listens to see if
channel you chose is clear before it allows it to be turned on.
Seeker can automatically lock onto any channel set on Tracker II.
Tracker II’s LCD screen shows memory position 2, that channel
is set at 52, and exact frequency of that channel. “10.01V” is
transmitter voltage.
February 2004 53
02sig2.QXD 11/25/03 1:04 pm Page 53
each function the LCD screen will provide
a numerical trim position. This is strictly
for reference purposes. Remember that
whatever trim you use on a particular
model to achieve level flight will be stored
in the computer and will remain until you
make changes.
On this particular transmitter, the fifth
and sixth channel functions do not have
trim. Also, on the CH 3 throttle function
the trim only operates when the control
stick is down close to minimum throttle.
This is so you can set your fueled engine
carburetor for the lowest possible idle
speed yet not stall the engine. Frank
Granelli will go into this feature.
The remaining menu items cover
certain mixing functions. There is a
programmable mixing (“P.MIX”) circuit
that will let you combine any two control
functions. I like to use this for coupled
aileron and rudder on some models. When
you apply ailerons to bank the model, the
rudder will respond to that single
command.
Several wing-mix (“W.MIX”) functions
can provide such things as elevon control
(“EL”) that will mix aileron and elevator
for flying wings or delta-wing models. The
flaperon (“FP”) function makes both
ailerons drop down for flap-type control. A
V-tail (“V”) mixing function provides a
rudder and elevator effect, as on a Scale
Beechcraft Bonanza. I won’t get into these
mixer functions in any detail because you
probably won’t be using them right away.
Quite a few computer-driven RC
transmitters include multimodel-type
programming; they offer menus
specifically for fixed-wing aircraft, for
helicopters, and in some cases for
sailplanes. This makes for some difficult
menu searching. Also, the switches are
marked three ways, making identification
difficult. I chose the T6EXA radio because
it has one menu and is intended
exclusively for fixed-wing aircraft.
Many of these computer RC
transmitters draw upward of 200 mA of
current. It is still common to see 600 mAhcapacity
Ni-Cd batteries supplied with
these systems, but in today’s hobby market
we are seeing NiMH batteries in the same
AA size with capacities up to 1100 mAh
and more.
Batteries such as these are available
from suppliers such as Batteries America
and SR Batteries. They even provide the
mating connectors for your particular
brand of transmitter. If you want more
capacity with which to operate your
transmitter for longer periods of time,
these higher-capacity replacement packs
are the way to go.
Just remember from my “Battery
Basics” article (in the October 2003 Model
Aviation) that you must charge these
batteries at the rate of C/10 (capacity
divided by 10). An 1100 mAh battery
would have to be charged overnight at 110
mA. To obtain that kind of current you
will need a variable output charger, such
as the Ace R/C Digital Dual Variable
Charger.
A number of computer transmitters
currently on the market employ a
synthesizer: a circuit that allows you to
dial up any one of the 50 channels
available for flying model aircraft. You
can purchase the Hitec Eclipse transmitter
with Hitec’s Spectra synthesized module.
This module plugs into the rear of the
transmitter case. To change channels, you
unplug the module and rotate two tiny
dials to obtain any channel from 11 to 60.
The Eclipse is also one of the
transmitters that lets you select high or low
FM deviation. That means you can operate
any FM RC receiver on the market with
this transmitter (regardless of the deviation
or the channel number).
Polk’s Modelcraft Hobbies has gone
one better with its Tracker II computerdriven
transmitter, which accommodates
more than 90 memory positions. A
synthesizer lets you select any one of the
50 RC aircraft channels using the LCD
screen so you don’t have to remove a
module and twist any dials. You can also
enter the channel number for each model
into the memory along with the proper
deviation.
When you first turn on the Tracker, a
built-in scanning receiver (right inside the
54 MODEL AVIATION
02sig2.QXD 11/25/03 1:04 pm Page 54
transmitter) scans the operating channel
before allowing it to go on the air. The
Polk’s Seeker companion receiver can
listen for an FM signal and then set itself
to that channel. With this concept you
could switch channels every flight and
never have to wait for an available
channel.
The fact that these computer-driven
transmitters can store control data for
many models means that you will need
many more receivers (one for each model)
but only one transmitter. Generally, the
RC manufacturers would like to sell you
an entire system: transmitter, receiver, and
servos. Through the years, many of these
manufacturers have priced airborne packs
(receiver and servos) at practically what it
costs for a full system.
More recently, companies have come
out expressly with aftermarket receivers
and servos that will work from almost any
computer-driven transmitter. FMA Direct
has a complete line of receivers and
servos. It even has a micro-size dualconversion
receiver (the M5) that weighs
0.35 ounce! Using aftermarket
microreceivers and microservos is
commonplace today, especially with
parking-lot and indoor RC flyers.
When mixing and matching computer
transmitters, receivers, and servos, you
will have to contend, to a degree, with
connector polarity. Connectors used on
receivers, switch harnesses, and servos
now follow the same convention.
On three-pin servo connectors, one
outside pin is battery negative, the center
pin is battery positive, and the other
outside pin is the signal. Plug it in one
way, and the servo works. Reverse the
connector (some have keys that prevent
this possibility), and the servo does not
work.
One thing is for sure: you cannot blow
out that servo with this type of polarity
convention. Years ago this was much
more of a problem. The only connector
that is still different is the charger plug on
the JR transmitters; the center pin and
outside connection are different on this
plug than on all others in the RC hobby
industry.
For the More Advanced RC Pilot: Most
of us fly on one of the 50 RC channels that
the Federal Communications Commission
(FCC) has made available expressly for
the control of model aircraft. With 50
channels to choose from and added
features such as synthesizers with dial-up
channel-selection capabilities, you never
have to wait very long to make a flight.
However, you may see certain
concentrations of channels at local flying
fields. One possibility to avoid a “channel
traffic jam” is to obtain an FCC ham radio
license and then operate on the Amateur
Radio Service 6-meter band (50 MHz).
Many RC manufacturers offer systems on
10 channels near 50 MHz.
If you are interested in what it takes to
become a ham and practically be able to
fly on your own channel, contact the
national organization (which is like our
AMA). It is the American Radio Relay
League, 225 Main St., Newington CT
06111; Tel.: (880) 594-0200; Web site:
www.arrl.org.
My articles in this series began with the
March 2003 Model Aviation. Look for
Frank Granelli and the glow-fueled-model
input for months to come. I expect to do
several “guest spots” on subjects such as
parking-lot/backyard flying, indoor RC,
Lithium-Polymer batteries and their
application, and some FAQs (frequently-
56 MODEL AVIATION
asked questions), which will be published
next month.
Keep in mind that this series is posted on
the Model Aviation portion of the AMA’s
Web site, at http://modelaircraft.org/mag/
index.htm. MA
Bob Aberle
Manufacturers:
Ace Hobby Distributors, Inc.
2055 Main St.
Irvine CA 92614
(949) 833-0088
Fax: (949) 833-0003
www.acehobby.com
Airtronics Inc.
1185 Stanford Ct.
Anaheim CA 92805
(714) 978-1895
[email protected]
www.airtronics.net
Batteries America
2211-D Parview Rd.
Middleton WI 53562
(800) 308-4805
[email protected]
www.batteriesamerica.com
FMA Direct
5716A Industry Ln.
Frederick MD 21704
(800) 343-2934
Fax: (301) 668-7619
[email protected]
www.fmadirect.com
GWS (also sold by Horizon Hobby)
Balsa Products
22 Jansen Ave.
Iselin NJ 08830
(732) 634-6131
www.balsapr.com
Hitec RCD (and Multiplex)
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
www.horizonhobby.com
SR Batteries Inc.
Box 287
Bellport NY 11713
(631) 286-0079
Fax: (631) 286-0901
[email protected]
www.srbatteries.com
Tower Hobbies (Hobbico and Futaba
radios)
Box 9078
Champaign IL 61826
(800) 637-6050
www.towerhobbies.com
02sig2.QXD 11/25/03 1:05 pm Page 56

46 MODEL AVIATION
Advanced
THIS IS MY 10TH
installment in this initial
phase of the “From the
Ground Up” series. I’ll
be back next month with
some frequently-asked
questions and in the
April issue the emphasis
will shift to fueled models under Frank
Granelli’s expert tutelage.
At the beginning of this series I
discussed some of the basic Radio
Control (RC) systems as an overall
introduction to the model-aircraft
hobby. To keep it simple and
inexpensive, I selected a basic threechannel
transmitter with a single
control stick. I use several of these
systems for my flying, so please don’t
worry; I didn’t recommend that you
buy something that would quickly
become obsolete.
As the series progressed I described
the Hitec Neon three-channel system,
then the electric power system, and
then the Aero Craft Pogo as a firsttime
(Almost Ready-to-Fly) training
aircraft.
My student Jay Federman had
already done a bit of flying on his
own, and he owned a four-channel,
dual-stick RC transmitter. When we
flew the Pogo for the first time, using a
trainer cable, Jay had to hold the Neon
transmitter since it was the one
broadcasting the signal. The master
control was my transmitter (a dualstick-
assembly four-channel unit),
which I held as the instructor pilot.
Jay got confused because the
throttle lever is on the rear of the case
(of the three-channel transmitter) and
it operates with a side-to-side motion.
He had done some flying using a leftside
control stick that moved up for
high speed and down for idle speeds.
I recognized this problem right
away, and many readers wrote in to
“scold” me for having suggested a
three-channel RC transmitter to a
beginner. Admittedly, as you progress
to four-channel (“full house,” as we
call it: elevator, aileron, rudder, and
throttle control), the throttle control
will be on the left stick and is operated
with an up-and-down motion.
I guess some apologies are in order.
Just keep in mind that the threechannel
RC system will never become
obsolete. It is well suited for my RC
sailplanes, parking-lot flyers, and
indoor RC.
I’m getting into more advanced RC
systems at this time because eventually
you will want to, and when you do you
will quickly appreciate some of the
extra features they can offer. You will
also be pleased to know that many of
these advanced radios are simple to
operate and are comparatively
inexpensive. So let’s get into it.
A basic RC transmitter, be it a threeor
four-channel-function unit, will not
be what we call a “computer” or
microprocessor-type radio. It will not
have a Liquid Crystal Display (LCD)
screen that allows you to set the
special commands or controls.
Most basic transmitters have servo
reversing, and a few might even offer
dual rate control on two-channel
functions. Servo direction is usually
changed with the flip of a tiny switch
(unplugging and rotating a cable on the
Hitec Neon). Dual rate control cutback
is adjusted by rotating a small
potentiometer control (dial). These
basic radios have a few switches and
potentiometers (dials) but no internal
computer circuitry and certainly no
New Airtronics VG6000A is popular
entry-level computer RC transmitter. It
will be featured in an MA product
review in the future.
02sig2.QXD 11/25/03 12:59 pm Page 46
memory circuits.
An advanced RC transmitter has an
internal computer chip that contains a
great deal of stored program information
in its memory circuits. It can also store
your control inputs, allowing you to
operate several models from a single
transmitter.
You can tell that it is a computer-driven
system because it has an LCD screen on
the front of the transmitter case. (One
exception is the FMA Direct T-80RF,
which is just a small step up from a basic
unit). The LCD screen displays a variety
of parameters; some are basic and
preplanned for you, and others you can
call up from a menu system that is
programmed into the transmitter.
How you access these menus, make
changes, and store the new inputs in the
memory is what an advanced RC
transmitter is all about. Once learned, you
February 2004 47
RC Systems
Typical RC transmitters (L-R): Hitec Neon three-channel (single
control stick); Hitec Laser 6, which has two control-stick
assemblies but is basic—not a computer radio; Futaba T6EXA
entry-level computer radio; Hitec Laser 6, which is computer
driven and has channel synthesizer.
L-R: Futaba T6EXA computer transmitter is covered in text. Hitec
Eclipse transmitter can be set for high or low FM deviation and
with Spectra synthesized module can dial up any of 50 RC
channels for models. Polk’s Tracker II has all Eclipse features,
but you don’t have to remove module to change channels.
Left: Rear of Hitec Neon three-channel single-stick transmitter.
Pointer shows location of throttle-control lever which must be
moved side to side to adjust engine/motor speeds. Right: Futaba
T6EXA computer transmitter, which has two control-stick
assemblies. Throttle control is obtained from left stick and
operated in up-and-down movement (for high and low throttle
settings).
Futaba T6EXA is roughly $180 from Tower
Hobbies. Full system has receiver, four
servos, full Ni-Cd battery packs.
by Bob Aberle
The JR XP662 distributed by Horizon Hobby is a popular entrylevel
Radio Control computer transmitter.
Photos courtesy the author
d
02sig2.QXD 11/25/03 12:59 pm Page 47
will have many more control features available for your use. You
can start with an advanced RC transmitter, but use only basic
controls until you gain a certain amount of experience.
Before I get into a computer-driven RC transmitter’s inner
workings, I must mention several more facts. Most modern RC
systems broadcast their signal on frequency modulation (FM).
Only a few amplitude modulation (AM) radio systems are still on
the market, and they are gradually disappearing.
You can’t intermix signals with these systems. An FM RC
transmitter can’t operate an AM RC receiver. Even within the FM
category, there are two types of signals that various manufacturers
employ. One is called FM deviation on the “low side.” Futaba,
Hitec RCD, FMA Direct, and GWS make use of this type of
signal. There is also FM deviation on the “high side,” as exhibited
in radios that JR Remote Control and Airtronics manufacture.
Keeping all of this in mind, a Futaba FM RC transmitter can
operate a Futaba FM RC receiver and FM RC receivers made by
Hitec, FMA Direct, and GWS. A JR FM RC transmitter can
operate a JR FM receiver and an Airtronics FM receiver.
Utilizing smart programming techniques, several RC
transmitters are able to select “high” or “low” FM deviation. This
can be a bonus since one transmitter can be used to operate almost
any brand of RC FM receiver on the hobby market, provided it is
on the same frequency (RC channel). Later I will mention an even
more sophisticated RC transmitter that uses a synthesizer which is
capable of dialing up any of the 50 RC channels available for
model aircraft.
I hate to get complicated early on, but in FM RC equipment
there is one other type known as pulse code modulation (PCM). It
is a technique in which a special digital code is added to the FM
signal. It provides much greater interference rejection than regular
FM, but it is usually only offered on the expensive, top-of-the-line
radio systems. These PCM systems also provide a fail-safe feature
that adjusts the controls to preset positions and reduces the engine
throttle if interference is experienced.
You should also know that each manufacturer uses its own
dedicated digital code, so you must stay with one brand for the
transmitter and receiver; you can’t intermix these units.
Types of Advanced RC Systems: You have already been
introduced to the basic radio. There are also “first step” computerdriven
RC transmitters. These entry-level systems offer many
extra control features, are relatively easy to use, and are
comparatively inexpensive (full systems range from $180 to
$250).
Several manufacturers offer a further step into the computerradio
market with systems ranging from $300 to $500. These offer
more features than the first-echelon systems but add a certain
amount of complexity. For the all-out expert competition-minded
pilot, there are top-of-the line radio systems that cost as much as
$1,000 and more. That won’t be for you for some time yet!
The First-Step Computer-Radio System: All of the popular RC
manufacturers—including Airtronics, FMA Direct, Futaba
(Hobbico), Hitec RCD/Multiplex, and JR (Horizon Hobby)—have
these entry-level computer-radio systems. Some of the big mailorder
hobby companies also offer “house radios,” but they are
generally made by the manufacturers I just listed.
The model numbers of these first-step radios are important for
identification purposes. For instance, the Airtronics VG6000 has a
new, innovative menu system. I expect to review this radio in
Model Aviation in the near future.
The Futaba T6EXA is simple and affordable (roughly $180!),
and this is the one I will explain in depth in a moment. Also
popular are the Hitec RCD Flash 5 X and Eclipse models and the
JR XP662. I have to admit that at this time I have little experience
with the new Hitec/Mulitplex systems from Europe.
You do not need to use any of the special features on these
first-level computer radios right away. You can turn off or inhibit
the extras while you learn to fly your first few RC models.
Futaba T6EXA: The heart of any computer-radio system is the
transmitter, and that is what I will discuss. Refer to the photos as I
proceed. Some photos are of the LCD screen on the T6EXA
transmitter, and others are of the illustrations in the Futaba
instruction manual (for added clarity).
Most RC-system manufacturers include their instruction
manuals on their Web sites. They are posted as PDFs (Portable
Document Formats) for viewing, or even printing, purposes. You
can access the Futaba T6EXA manual at www.futabarc.
com/manuals/6exa-manual.pdf.
The six-channel-control-function Futaba T6EXA transmitter
offers:
• low-voltage alarm
• digital trims
• six model memory positions
• the ability to reset any memory slot to the factory-default
positions
48 MODEL AVIATION
Upper left portion of Futaba T6EXA transmitter case. Switch on front
is for “CH.5 GEAR”—a nonproportional auxiliary channel. At top left
corner is “TRAINER/THT CUT”: a momentary contact switch you
pull forward to operate; when you let go, it springs back rearward. It
operates trainer cable function or can kill a glow-fueled engine.
Top right corner of transmitter case. “AIL/ELEV D/R” switch
turns dual rate, exponential rate control on or off. On top is
“CH.6 FLAPS” knob you turn to operate proportional sixth
channel function. You can use it to operate flaps, spoilers, or any
other auxiliary function.
02sig2.QXD 11/25/03 1:00 pm Page 48
Lower front part of Futaba T6EXA has LCD screen, control
necessary to operate built-in computer system. To left of screen
are “MODE,” “SELECT” switches. At right is “DATA INPUT”
switch; it rocks up or down for + or – control inputs. Each
channel function (six total) is listed next to DATA INPUT switch.
To enter menu system, turn on power then press and hold down
MODE and SELECT switches for roughly two seconds. “MODEL”
memory position (1 through 6) is first item to come up and will
flash. Press DATA INPUT switch to scroll around six positions.
This is how you select correct position to operate each model.
If you press SELECT while in MODEL portion of menu, letters
“CL” will flash on screen. Press DATA INPUT switch in either
direction (+ or –) and hold for a second to erase all control inputs
to this position and restore them to factory settings. This is
especially helpful when setting controls for new model.
This is the typical screen for reversing the servo direction for any
of the six channel functions.
When you initially turn on transmitter, basic screen display will
appear. Small “1” in upper right corner is current model-memory
position. Larger “8.5v” is transmitter battery voltage. At 8.5 volts,
audible alarm will sound and battery icon on screen will flash,
telling you to stop flying and recharge battery.
Since you can’t name models on LCD screen, Bob pastes list to
rear of transmitter. You could also put a note on your model,
such as “Futaba T6EXZ, No. 1”. That way you would be alerted to
take correct transmitter to field and make sure it is set on model
memory position 1.
February 2004 49
02sig2.QXD 11/25/03 1:01 pm Page 49
• dual rate control of two channel functions
• exponential rate control of two channels
• endpoint adjustment (EPA) on all channels
• servo reversing on all channels
• trim memory and position
• programmable mixing of any two channel functions
• wing mixing (elevons, flaperons, V-tail)
• throttle cut for glow-engine operation and provision for trainer
cable
It’s all there in that one transmitter case! Keep in mind that six
memory positions means that you can fly as many as six models
from this transmitter.
Looking at the T6EXA’s front panel, you will see the two dual
axis control-stick assemblies. When flying with only three
channels, the right stick operates the rudder and elevator and the
left stick moves up and down for the throttle control. All control
sticks have spring return to the neutral position except the throttle,
which has a ratchet device to hold the last position.
When using four-channel control, the right stick usually has
the aileron and elevator functions and the left stick assembly
provides rudder and throttle. For years this stick configuration has
been called Mode 2. A few pilots (mostly in Europe) still fly what
is called Mode 1. I have no intention of getting into that other
mode at this time, but the T6EXA is capable of Mode 1 control as
explained in the manual if that is your preference.
In addition to the four basic flight controls, a fifth channel is
available to operate a retractable landing gear, as a towhook
release on a sailplane, or as any other auxiliary function you
might think of. It is not a proportional control channel; the servo
goes to one side or the other (no neutral position). The fifth
channel is operated by the “CH.5 GEAR” switch at the upper left
corner of the case.
At the top right corner of the transmitter case is a knob that
proportionally operates a sixth channel function; it is identified as
“CH.6 FLAPS.” This channel is primarily used as a flap or spoiler
control, but, again, you could use it for a variety of auxiliary
functions.
There are several more switches on the front panel. At the
upper right is one identified as “AIL/ELEV D/R.” It
simultaneously turns on or off dual rate control for the
aileron/elevator (or rudder/elevator for three-channel control).
This switch also turns on/off the special exponential rate control
to the same two channel functions.
At the top left corner of the case is a momentary contact
(spring return) switch to operate the trainer-cable function. The
“From the Ground Up” installment in the September 2003 issue
(on page 71) has a more detailed discussion about using a trainer
cable.
When momentarily pulled forward and released, that trainercable
switch will act as an engine-kill (stop) switch. This is
helpful when your transmitter employs digital trim, as does the
T6EXA. By pulling this switch, you don’t have to operate the
throttle digital trim lever to completely kill your glow-fueled
engine. (Frank Granelli will explain this in more depth later in
this series.)
We’ve finally gotten to the computer system. At the lower
50 MODEL AVIATION
Dual rate control allows you to reduce amount of control throw
from 100% to 0%. Then by throwing D/R switch on front panel,
you can obtain reduced control throw in flight. Dual rate control
is only available on CH1 (aileron or rudder) and CH2 (elevator).
While in dual rate menu, if you press SELECT beyond CH2 you
will come to exponential rate control. You will see =/– sign
followed by 0%. As you reduce percentage in negative direction
(“–5,” “–10,” “–15,” etc.), controls react slower around neutral
position, giving “softer” feel in flight. This feature is also available
on CH1 and CH2 and can be combined with dual rate control.
EPA (endpoint adjustment) is probably the transmitter’s most
worthwhile feature and will be popular even with a rank beginner.
It lets you adjust control throw of any servo, and it will let you do
that independently. You can set more up- than down-elevator!
02sig2.QXD 11/25/03 1:01 pm Page 50
portion (middle) of the transmitter case is
an LCD screen. To the left of the screen
are two push-button switches identified as
“MODE” and “SELECT.” To the right is a
data-input switch that moves up (+) and
down (–). Next to this switch the six
channel controls are listed by number and
function, such as “CH1=Aileron,”
“CH2=Elevator,” etc.
When you first turn on the transmitter
power, an initial or basic display will
appear on the LCD screen. It will have a
small number (1 through 6) at the upper
right and a larger number, such as 10.0v, at
the lower right. The smaller number tells
you which computer-memory position is
currently in operation.
The larger number is this particular
transmitter’s battery voltage. At 10.0 volts
or slightly higher, the transmitter battery is
close to full charge. When the voltage falls
to 8.5, an audible alarm will sound and a
battery icon will flash on the LCD screen.
This is a warning to land your model
immediately because you only have
several minutes of charge remaining. At
that point you recharge the battery or
substitute a freshly charged battery pack.
To access the various control features,
you must get into the T6EXA computer
menu. Many of these computer radios have
two menus; one is for basic programming
and selection of the model memory and the
other contains all of the detailed control
features. I chose the T6EXA because it
only has one menu, which makes it simple.
With the transmitter power on, press
the MODE and SELECT switches (keys)
and hold them for a second or two. The
first thing to show up on the LCD screen is
the “MODEL” memory position. A largesize
number (1 through 6) will flash on the
screen. You change the model number by
pressing the data-input (+ or –) switch.
This will allow you to scroll up to 6 or
down to 1.
On some computer transmitters you can
add a model’s name to the memoryposition
number for identification
purposes, but that feature isn’t available on
this unit. As an alternative I pasted a list
on the rear of the case indicating each
model and the number assigned to it.
You must be especially careful when
selecting the correct model-memory
position. If you don’t select the right
number, you may find your controls
reversed and a crash could easily result.
On the other hand, remember that you can
operate as many as six different aircraft
from this transmitter.
While still in the MODEL portion of
the menu, if you press SELECT you will
see a “CL” flash on the LCD screen along
with the model memory-position number.
Pressing either data-input key (+ or –) for
February 2004 51
This is how EPA function looks when called up on LCD screen.
You can select CH1 or CH2, then amount of control-throw
reduction (from 100% to 0%—which you won’t be doing!).
Amount of trim used on any of four main channel functions can
be displayed in this part of menu. Any trim you set in flight is
automatically saved until you change it on later flight. While in
this portion of menu, you can add or subtract trim by following
numerical position displayed on LCD screen.
P.MIX allows you to mix any two channel functions. You could
have small amount of rudder control when applying aileron to
smooth out or coordinate turns. “Inh” indicates that P.MIX is
turned off or inhibited.
W.MIX lets you set up programmed mixing for elevon control,
flaperons, or V-tail operation (as explained in text).
02sig2.QXD 11/25/03 1:01 pm Page 51
52 MODEL AVIATION
roughly two seconds will erase any inputs
stored in that memory position. Controls
will then be restored to factory-default
settings. This can be helpful when you are
setting up controls for a new model.
Moving along the menu, press MODE
and you come to “REVERSE.” This
function will let you reverse any servo’s
direction. Press SELECT to choose the
channel function you want to reverse (1 to
6), and then press + or – to select the
“NOR” (normal) or “REV” (reverse) servo
direction. Press MODE again, and the
“D/R” (Dual Rate) function comes up. The
menu keeps going in one direction, as in a
loop. If you miss an item, keep pressing
MODE until it appears again.
Dual rate control applies only to
channels 1 (aileron or rudder when flying
with three channels) and 2 (elevator). The
LCD screen will show CH 1 or CH 2,
which you choose by pressing SELECT.
Then you will see 100%, meaning that the
control is set for “full,” or maximum
throw. Use the data-input – switch to
reduce the control to something less than
full.
Now that AIL/ELEV D/R switch at the
upper right comes into play. With it in the
down position, you want your aileron or
rudder and your elevator at full throw, or
100%. Move that switch to the upper
position, and the reduced throw that you
just set (something less than 100%) will
appear. Keep in mind that the AIL/ELEV
D/R switch affects the two channels at the
same time on this transmitter; you can’t
separate the aileron and elevator functions.
Dual rate control can be helpful on
faster models. At takeoff and landing
speeds you have the controls set at full, or
100%. During the flight, you can flip the
D/R switch to the up position and the
controls will be reduced somewhat,
making the airplane easier to fly at high
speeds.
When pressing the SELECT switch
while in this same D/R function, after D/R
you will come to an added feature called
exponential rate control. When you get to
this function you will see a plus and minus
sign and 0% on the LCD screen. If you
then press the minus switch, you will see a
negative number such as 5, 8, 10, 15, etc.
These negative numbers make the initial
servo movement less than normal.
What happens is that the control
response is slower or “softer” around the
neutral position. By selecting that negative
number, you can tailor the feel to suit you
and your model. I realize that this sounds
slightly complicated at first, but you will
learn as you gain experience with the
system. Keep in mind that with the
T6EXA you can have dual rate and
exponential rate together or you can have
dual rate or exponential rate separately.
The next menu item (press MODE) is
EPA. This is available on all six channels.
It is especially nice to have EPA on the
throttle channel when using a fueled
engine; it makes high and low carburetor
adjustments so easy.
With EPA you can set the servo control
throw to the exact amount of control
required. You can even set the elevator for
more up than down or more right aileron
than left. This is probably the best feature
in a computer-radio system. It is the
control function you will use the most.
As you go through the menu and make
control adjustments, your inputs are saved
automatically in the computer each time
you move on to the next menu item or if
you turn the power off. Afterward, any
time you call up that particular model
memory position, the control inputs you
made will be right there for you (stored in
the computer memory).
The next menu item is important
because it involves the trim function. Each
of the four main channels has a separate
trim switch. On this transmitter the trim is
the more modern digital variety. The
purpose of trim is to allow you to set your
model for straight and level flight with
your hands off of the control sticks. You
“rocker” the trim switches left or right or
up and down to achieve level flight
characteristics.
Once you have a model adjusted for
level flight, you can call up the “TRIM”
menu item. It will allow you to select any
one of the four channels that provide trim
(aileron, elevator, rudder, or throttle). For
02sig2.QXD 11/25/03 1:01 pm Page 52
Transmitter’s battery-compartment cover has been removed and
battery pack (red case) partially removed. Battery has only 600 mAh
capacity—enough to operate transmitter for roughly two hours.
You could substitute packs with almost double the capacity that
still fit in compartment. If you go to higher capacity, you will have to
buy variable output charger such as ACE R/C DDVC shown.
These are some RC-system connectors with which you may
come in contact. At top is transmitter charging jack. In middle are
mating halves of receiver battery cables (only two wires
employed). At bottom is servo connector with three wires.
Convention today throughout hobby industry is to have negative
pin in middle. If servo connector is plugged in backward (hard to
do!), servo will not work but will not be damaged.
To show you that Bob also thinks about receivers, at top is his
first, from 1953—the Miller—which was featured in MAN that
year. It weighed 5 ounces and offered only single-channel control
of rudder. In middle are typical, current Futaba and Airtronics
dual-conversion RC FM receivers. At bottom right is FMA Direct
aftermarket receiver. At bottom left is popular 0.2-ounce GWS
R4P micro four-channel receiver.
Spectra synthesized module removed from Hitec Eclipse
transmitter. By rotating two dials shown, you can obtain any of
50 channels available for model use on 72 MHz band.
Polk’s Modelcraft Hobbies’ new Tracker II transmitter, companion
Seeker receiver. Transmitter is synthesized to operate on all 50
channels. Scanning receiver inside transmitter listens to see if
channel you chose is clear before it allows it to be turned on.
Seeker can automatically lock onto any channel set on Tracker II.
Tracker II’s LCD screen shows memory position 2, that channel
is set at 52, and exact frequency of that channel. “10.01V” is
transmitter voltage.
February 2004 53
02sig2.QXD 11/25/03 1:04 pm Page 53
each function the LCD screen will provide
a numerical trim position. This is strictly
for reference purposes. Remember that
whatever trim you use on a particular
model to achieve level flight will be stored
in the computer and will remain until you
make changes.
On this particular transmitter, the fifth
and sixth channel functions do not have
trim. Also, on the CH 3 throttle function
the trim only operates when the control
stick is down close to minimum throttle.
This is so you can set your fueled engine
carburetor for the lowest possible idle
speed yet not stall the engine. Frank
Granelli will go into this feature.
The remaining menu items cover
certain mixing functions. There is a
programmable mixing (“P.MIX”) circuit
that will let you combine any two control
functions. I like to use this for coupled
aileron and rudder on some models. When
you apply ailerons to bank the model, the
rudder will respond to that single
command.
Several wing-mix (“W.MIX”) functions
can provide such things as elevon control
(“EL”) that will mix aileron and elevator
for flying wings or delta-wing models. The
flaperon (“FP”) function makes both
ailerons drop down for flap-type control. A
V-tail (“V”) mixing function provides a
rudder and elevator effect, as on a Scale
Beechcraft Bonanza. I won’t get into these
mixer functions in any detail because you
probably won’t be using them right away.
Quite a few computer-driven RC
transmitters include multimodel-type
programming; they offer menus
specifically for fixed-wing aircraft, for
helicopters, and in some cases for
sailplanes. This makes for some difficult
menu searching. Also, the switches are
marked three ways, making identification
difficult. I chose the T6EXA radio because
it has one menu and is intended
exclusively for fixed-wing aircraft.
Many of these computer RC
transmitters draw upward of 200 mA of
current. It is still common to see 600 mAhcapacity
Ni-Cd batteries supplied with
these systems, but in today’s hobby market
we are seeing NiMH batteries in the same
AA size with capacities up to 1100 mAh
and more.
Batteries such as these are available
from suppliers such as Batteries America
and SR Batteries. They even provide the
mating connectors for your particular
brand of transmitter. If you want more
capacity with which to operate your
transmitter for longer periods of time,
these higher-capacity replacement packs
are the way to go.
Just remember from my “Battery
Basics” article (in the October 2003 Model
Aviation) that you must charge these
batteries at the rate of C/10 (capacity
divided by 10). An 1100 mAh battery
would have to be charged overnight at 110
mA. To obtain that kind of current you
will need a variable output charger, such
as the Ace R/C Digital Dual Variable
Charger.
A number of computer transmitters
currently on the market employ a
synthesizer: a circuit that allows you to
dial up any one of the 50 channels
available for flying model aircraft. You
can purchase the Hitec Eclipse transmitter
with Hitec’s Spectra synthesized module.
This module plugs into the rear of the
transmitter case. To change channels, you
unplug the module and rotate two tiny
dials to obtain any channel from 11 to 60.
The Eclipse is also one of the
transmitters that lets you select high or low
FM deviation. That means you can operate
any FM RC receiver on the market with
this transmitter (regardless of the deviation
or the channel number).
Polk’s Modelcraft Hobbies has gone
one better with its Tracker II computerdriven
transmitter, which accommodates
more than 90 memory positions. A
synthesizer lets you select any one of the
50 RC aircraft channels using the LCD
screen so you don’t have to remove a
module and twist any dials. You can also
enter the channel number for each model
into the memory along with the proper
deviation.
When you first turn on the Tracker, a
built-in scanning receiver (right inside the
54 MODEL AVIATION
02sig2.QXD 11/25/03 1:04 pm Page 54
transmitter) scans the operating channel
before allowing it to go on the air. The
Polk’s Seeker companion receiver can
listen for an FM signal and then set itself
to that channel. With this concept you
could switch channels every flight and
never have to wait for an available
channel.
The fact that these computer-driven
transmitters can store control data for
many models means that you will need
many more receivers (one for each model)
but only one transmitter. Generally, the
RC manufacturers would like to sell you
an entire system: transmitter, receiver, and
servos. Through the years, many of these
manufacturers have priced airborne packs
(receiver and servos) at practically what it
costs for a full system.
More recently, companies have come
out expressly with aftermarket receivers
and servos that will work from almost any
computer-driven transmitter. FMA Direct
has a complete line of receivers and
servos. It even has a micro-size dualconversion
receiver (the M5) that weighs
0.35 ounce! Using aftermarket
microreceivers and microservos is
commonplace today, especially with
parking-lot and indoor RC flyers.
When mixing and matching computer
transmitters, receivers, and servos, you
will have to contend, to a degree, with
connector polarity. Connectors used on
receivers, switch harnesses, and servos
now follow the same convention.
On three-pin servo connectors, one
outside pin is battery negative, the center
pin is battery positive, and the other
outside pin is the signal. Plug it in one
way, and the servo works. Reverse the
connector (some have keys that prevent
this possibility), and the servo does not
work.
One thing is for sure: you cannot blow
out that servo with this type of polarity
convention. Years ago this was much
more of a problem. The only connector
that is still different is the charger plug on
the JR transmitters; the center pin and
outside connection are different on this
plug than on all others in the RC hobby
industry.
For the More Advanced RC Pilot: Most
of us fly on one of the 50 RC channels that
the Federal Communications Commission
(FCC) has made available expressly for
the control of model aircraft. With 50
channels to choose from and added
features such as synthesizers with dial-up
channel-selection capabilities, you never
have to wait very long to make a flight.
However, you may see certain
concentrations of channels at local flying
fields. One possibility to avoid a “channel
traffic jam” is to obtain an FCC ham radio
license and then operate on the Amateur
Radio Service 6-meter band (50 MHz).
Many RC manufacturers offer systems on
10 channels near 50 MHz.
If you are interested in what it takes to
become a ham and practically be able to
fly on your own channel, contact the
national organization (which is like our
AMA). It is the American Radio Relay
League, 225 Main St., Newington CT
06111; Tel.: (880) 594-0200; Web site:
www.arrl.org.
My articles in this series began with the
March 2003 Model Aviation. Look for
Frank Granelli and the glow-fueled-model
input for months to come. I expect to do
several “guest spots” on subjects such as
parking-lot/backyard flying, indoor RC,
Lithium-Polymer batteries and their
application, and some FAQs (frequently-
56 MODEL AVIATION
asked questions), which will be published
next month.
Keep in mind that this series is posted on
the Model Aviation portion of the AMA’s
Web site, at http://modelaircraft.org/mag/
index.htm. MA
Bob Aberle
Manufacturers:
Ace Hobby Distributors, Inc.
2055 Main St.
Irvine CA 92614
(949) 833-0088
Fax: (949) 833-0003
www.acehobby.com
Airtronics Inc.
1185 Stanford Ct.
Anaheim CA 92805
(714) 978-1895
[email protected]
www.airtronics.net
Batteries America
2211-D Parview Rd.
Middleton WI 53562
(800) 308-4805
[email protected]
www.batteriesamerica.com
FMA Direct
5716A Industry Ln.
Frederick MD 21704
(800) 343-2934
Fax: (301) 668-7619
[email protected]
www.fmadirect.com
GWS (also sold by Horizon Hobby)
Balsa Products
22 Jansen Ave.
Iselin NJ 08830
(732) 634-6131
www.balsapr.com
Hitec RCD (and Multiplex)
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
www.horizonhobby.com
SR Batteries Inc.
Box 287
Bellport NY 11713
(631) 286-0079
Fax: (631) 286-0901
[email protected]
www.srbatteries.com
Tower Hobbies (Hobbico and Futaba
radios)
Box 9078
Champaign IL 61826
(800) 637-6050
www.towerhobbies.com
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