RCMN 66

Product Review
Graupner/JR
MX22
radio system
by
Brian Green
There has always been a fundamental
difference between transmitters of European design and the others. This is typified
by Graupner transmitters which are
designed to be used with at least a neck
strap and preferably a transmitter tray with
the stick tips gripped between thumb and
forefinger. Compare this method to the
hand held types with the control sticks
operated by thumbs resting on the stick
tips.
Another difference is the software
programs where the Japanese software
dictates which switch will operate which
control. However this is slowly changing
with later JR models such as the PCM9X.
European software lets you choose to
assign which switch to which function.
This is what I would call flexible programming but what is its advantage?
The first benefit is you can have any
switches where they are easiest to operate.
For example, I fly mode two where the left
hand if often unoccupied. By using the
switches above the throttle stick, I never
have to take the fingers off the elevator/
aileron stick. Another is that it simply
reduces the pilot’s workload so lets look at
an example.
A scale model fitted with retractable
landing gear and flaps operated by a three
position switch. Flaps up, takeoff flap and
landing flap. The retracts are operated by a
two position switch.
After several test flights the model
needs more control surface travel when
slowed down on a landing approach. No
problem we have dual rates to accommodate this. We simply assign the landing
gear switch as the dual rate switch. With
gear down we now have the model’s
response we need and simply flick the
switch up after takeoff to retract the gear
and reduce the control throws for smoother
flying.
If the nosewheel steering is driven by a
mixer from the rudder channel, assign the
mix switch to the landing gear switch. With
gear up the nosewheel steering is inoperative and thus saving current drain on the
battery.
You’re on approach with gear down and
landing flap out. Too hot, gotta go around
as the stomach muscles tighten. Open the
throttle and get the flap to the takeoff
setting, now where is the flap switch? If the
landing flap switch position is coupled with
a control switch on the throttle stick that is
set to say two thirds open, simply open the
throttle to go around and the flaps automatically go the takeoff setting .
That is an example of flexible programming.
THE GRAUPNER MX22
Pictured left is the Graupner MC24 compared to the MX22.
Number 66. June-July 2004
The MX22 is a twelve channel programmable transmitter which can handle PCM20,
SPCM20, PPM18 and PPM24 modes of
transmission. In European terminology a
servo control is two channels not one,
hence the 20, 18 and 24 numbers are
divided by two to establish the number of
servo channels that can be controlled. PCM
modes will operate all Graupner and JR
PCM receivers while the PPM mode
operates either up to nine or twelve channel
FM PPM receivers as JR manufacture a
twelve channel PPM receiver for Graupner.
The TX frequency module plugs in
(36meg) while the TX battery is an eight
cell 1700mAh nickel metal hydride
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PRODUCT REVIEW: GRAUPNER/JR MX22 RADIO SYSTEM
The MX22
transmitter
exposed.
Adjustable stick
tension and throttle
ratchet.
Identical layout to
the PCM9X as only
the software is
different.
The fuse that
protects.
(NiMH).
The airborne equipment is straight JR.
NER649S PCM nine channel receiver, four
ES539 servos, standard JR switch harness
with charge socket and a four cell
1100mAh nicad battery. The wall mounted
240V charger is labelled 60mA and would
require more than the typical overnight
charge to fully charge both TX and RX
batteries. Of course any of the extensive
range of JR servos or receivers can be
ordered with the MX22 to customise the
unit for your specific needs. The stick setup
can be changed to any one of the four
modes and both aeroplane and helicopter
programs are catered for.
What Graupner has done is to take the
JR PCM9X transmitter mechanicals and
married it to their own software operating
twelve channels. (JR manufacture Graupner radios). As the heading picture indicates you get an attractive twin stick
transmitter in the traditional Japanese
Black and Silver livery. The twin sticks are
adjustable in length and spring tension and
each have digital trims. There are eight
switches, one of which is spring loaded off,
two are three position with the remainder
two position. Also on upper of the front
face are two, three position spring loaded
centre off controls. Each side of the
transmitter has a rotary slider control. So,
including the control sticks and trims, there
are twenty controls of one sort or another
for you to operate. The four buttons on the
left of the large LCD display are labelled
ENT, ESC, CLR and HLP while the rotary
cylinder on the right functions as either a
function or value selector. Pressing this
knob in, replicates the action of the ENT
key. All control switches are identified with
numbers and this really eases the programming task.
The comprehensive 160 page instruc-
tion manual is one of the best I have ever
seen with clear instructions and pictures
covering all aspects of the MX22 TX
operation. Also provided are 24 pages of
programming examples covering model
types and the more exotic programming
functions. In fact it could be used as a
reference manual for most programmable
transmitters.
As shipped, the MX22 TX will operate
a standard four channel model without any
programming other than changing the stick
or transmission mode if required as
controls five to twelve are unassigned. On
initial switch on the LCD will beep and
display a warning “fail safe setup.” This
will disappear after some ten seconds and
will not appear once the fail-safe function
has been set up..
The initial screen displays the model
number 1-30 and elapsed time, the battery
voltage in both numeric and graphic form,
an aeroplane or heli graphic to indicate the
model type, timer values and the position
The LCD display at switch on. <<Normal>> is the name of the current flight mode. On the left of the screen are the four
programming buttons with the rotary cylinder on the right. The lowere button marked help will display a help screen for the
currently selected function.
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PRODUCT REVIEW: GRAUPNER/JR MX22 RADIO SYSTEM
of the four digital trims. Pressing the ENT
button brings up the menu of functions that
will display only the functions applicable
to the model type. Rotating the cylinder
will cycle through the various functions
and pressing the cylinder in will select and
display that function.
From new the first step is to select the
Basic settings function where you can
enter your name and set the stick and
transmission modes. On this screen Expert
mode will either display all functions
(YES) or a limited number of functions
(NO) on the function menu. The stick and
transmission modes are global and will
appear in each new model as it is set up.
However they can be overridden in the
Base model setup function.
For a new model, the first operation is
select Model select and select either
aeroplane or heli type. The next step is to
select Base setup model. Here you can
enter the Model name, Stick mode,
Modulation and digital Trim steps. The
latter changes the trim button sensitivity
with a range of 1-10. One is most sensitive
where the servo output moves very little
for each trim beep and ten makes the servo
movement per step very coarse. Next step
is the Model type where the display shows
set up functions applicable to either
aeroplane or heli. This is typical of the
programming of the MX22 where only
applicable functions are displayed. If more
than four channel operation is required the
next step is select Control adjust where
channels from 5-12 are assigned and this
where the MX22 excels. Simply select the
desired channel and press or move the
desired switch or control to assign the
servo to this switch or control. In this menu
you can also set a global travel for the
servo and this will then equate to 100%
when the servo adjustment function is
selected. As an example, set channel 6 to
50% in Control adjust and then this will
be the distance the servo moves for the
100% value in the servo adjust function
where it can be finally adjusted.
After all required controls are assigned
in the Control adjust menu, programming
functions like servo direction, throttle trim
action, (trim action occurs at full or closed
stick or overall), assigning mixers or any of
the multitude of programming options can
be set up and here the extensive model set
up examples in the manual make the
procedure easy to follow. Also in this
menu you can set a transit time of up to 9.9
seconds for channels 5-12, ideal for flaps,
speed brakes or servo operated retractable
landing gear.
To demonstrate the ease of programming, we want three position flaps controlled by a three position switch, flaps up,
Number 66. June-July 2004
Simply press the ENT key at any time to bring
up the function menu. No need to hold any
keys down while switching the TX on.
This screen sets global values that are applied
for every new model created, either Aircraft or
Heli. the Expert mode YES displays all
functions. NO displays a limited range in the
function menu.
Here we name the model. Note that stick
and transmission modes set can be reset in
this screen. Trim steps sets the sensitivity
of the electronic trims.
Model type screen. Throttle trim position,
tail and wing type and brake channel are
set here. After this setupyou can go fly a
basic model.
The assignment of channels 5-12 are on
this screen. The display shows channel 7
as a flap channel controlled by the three
position switch 8. Flaps up 100%, takeoff
flap 55% and flaps down 100% with a
transit time of 5 seconds.
The preassigned mixer functions
displayed on this screen are dependant on
the wing or heli type.
Dual rate and Expo screen.
takeoff and landing positions. Use channel
7 or any unassigned channel for the flap
servo. In the Control adjust menu assign
Enter 7 to one of the three position
switches 7 or 8. Set the Offset % to the
required takeoff flap position and the flap
up and down positions with Travel %. Then
set the speed of the flap transition with the
Time setting where you can have equal or
separate transit times for flap up and down.
Assign a mixer to couple channel 7 to
elevator and set the mix value to compensate for any pitch change when the flaps
are lowered. The elevator trim movement
will occur at the same rate at the flap
movement. Using two flap servos? Say
channels 7 and 8. Two methods available,
follow the same procedure for Enter 8 as
for Enter 7 in the Control adjust menu or
use the Dual mixer function, two are
available, which will couple two servos to
one control. Either way you can individually set flap up, takeoff and down positions. This is pretty heavy stuff and so
simple.
Up to four flight phases can be programmed in each of the thirty model
memories making a total of 120 flight set
ups available, enough surely for the most
serious model flyer. Dual rates and
exponential can be individually set for each
flight phase and assigned to one or more
switches. And the dual rate/expo settings
are graphically displayed.
Special mention should be made of the
three position centre off controls 5-6 as
these maintain their respective settings for
each programmed flight phase. This means
they can be used as a trimming control for
any servo on channels 5-12 that is driven
by a mixer from the channels 1-4. For
example, with two aileron servos installed
that occupy channels 2 and 5, assigning
ENTER 5 to the CONTROL 6 in the
Control adjust menu will allow you to
adjust both ailerons up or down using the
Control 6 switch. You can set the travel %
in the Control adjust menu to limit the
amount the Control switch will move the
ailerons. In fact any input to channel 5 will
control both ailerons as flaps, a feature that
can be used to deflect both ailerons up to
slow down landing approach speeds.
Mixing is the forte of computer
transmitters and the MX22 has plenty of
options with four free linear and two multi
point curve mixers. As well as these, up to
twelve pre-defined wing mixers, up to ten
heli predefined mixers and two dual mixers
are available. The later mixers automatically couple two channels to one control,
for example two independent elevator or
flap servos. The travel direction, centre and
end points of each servo can be independently set. The channel one travel curve can
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PRODUCT REVIEW: GRAUPNER/JR MX22 RADIO SYSTEM
be set to produce a more linear throttle
response with three adjustable points in the
range. Pressing the ENT key will toggle
between a liner or curved smoother
response. In the Heli mode the curve can
be independently set for each flight phase.
Four timers are displayed on the screen,
one is the time the TX has been turned on
since the last charge, another the time the
particular model memory has been turned
on. The remaining two are a stop watch and
flight timer and can count up or down.
These timers are assigned to either an
external switch or a control switch. For
example, a retract switch or a throttle
channel control switch. The former will
start the watch when the gear is selected up
and the latter, when the throttle is opened.
You can combine any one of four control
switches with an external switch which will
either override or enable the control switch.
Another example is a counting up flight
timer that can be assigned to the momentary contact switch SW8. Flicking this
switch starts the timer, pressing the ESC
key stops it and pressing the CLR key
resets it.
Mention has been made of control
switches which are four software switches
that can be assigned to switch at any
control stick position. This is a very
The free mixers screen.
Set the mixer value here. This screen
example shows elevator to channel 8 mix
only occuring from centre to one end.
The mix only screen where you can set up
any channel to be disconnected from a
control and only driven from a mixer.
powerful feature that can automate many
pilot inputs as described in an earlier
example. Another example is to select
either dual rates or one of two expo curves
as a function of throttle position.
Another example, when using dual rates
To see the results of your programming,
this screen displays the twelve servo
positions and they will move when you
move the controls..
the servo travel is increased or reduced
across the entire range of servo movement.
So when high rate is selected the sensitivity
of the control response around centre is
increased. By assigning expo to the same
high dual rate switch, the servo response
around centre can be adjusted in the expo
function to simulate the low rate control
response.
Flight phases are a method of changing
a model’s configuration with the flick of a
switch. While I personally try and avoid
their use, many modellers love them. They
were originally developed for gliding
where you have specific tasks, launch,
thermalling, hunting for lift and landing.
The trailing edge of a typical high performance glider has at least two ailerons and
two flaps of which all can move as ailerons
and or flaps with various control throws to
suit. The control surface positions are
A page from the manual showing just some of the comprehensive heli set up procedures.
“Ah” if only all instruction manuals were like this one!
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PRODUCT REVIEW: GRAUPNER/JR MX22 RADIO SYSTEM
typically preset for the various flight
phases and switches are used to change
from one setting to another. The alternative
is to fiddle around with slider controls to
establish the required setting so it is much
easier and more reliable with switching.
Each flight phase is named and the
name appears on all applicable menu
screens including the main screen. When
flight phases are used there are global
functions that cannot be changed in a flight
phase, for example servo reversing. And
there are functions that can be changed. To
complicate the matter, there can be
functions that can be changed in a flight
phase but that may have the same setting in
all phases. A problem arises if you change
one of these latter functions in one phase
but neglect to change it in the other phases.
For a power model there is little
programming that cannot be accomplished
in a single flight phase, so that is why I
tend to avoid their use. But they are a very
powerful tool in automating flying tasks.
Fail-safe is available in PCM mode with
either hold or fail-safe in PCM20 and
SPCM20 modes. In both modes channels
1-8 fail-safe positions are programmable
with channels 9-10 remaining in neutral in
PCM20 and hold in SPCM20 modes. The
hold time can be set to 0.25, 0.5 or 1.0
seconds in PCM20 as well as battery
voltage fail-safe which operates when the
RX battery voltage drops to a predetermined level. A servo connected to channel
one in aeroplane or channel eight in heli
moves to either neutral or +-75% when a
battery fail-safe occurs.
A trainer system is an optional extra and
when fitted individual channels can be
assigned to the trainer transmitter. This
module also allows connection for data
transfer between two transmitters or a
transmitter and a PC with the appropriate
optional cable.
In summary the MX22 is a transmitter
capable of handling the programming tasks
of extremely complex models of up to
twelve channels with flexibility in physical
control location.. The programming task is
extremely logical., a task which is aided by
the comprehensive instruction manual.
With programmable transmitters simply
knowing how to program the functions is
one thing, knowing how to apply them to
improve a model’s performance is something else and again this is where the
manual excels with numerous examples of
what functions are used for.
A diagram in the manual shows the order and logic path for the controls.
Graupner/JR radios are distributed to
hobby shops by: O’Reilly Model Products,
42 Maple Ave. Keswick. SA. 5035. Phone:
08 8351 0544. Fax: 08 8371 0659
Number 66. June-July 2004
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