| FLY RC MAGAZINES REVIEW OF THE SPEKTRUM DX-7 |
SPEKTRUM
DX7 2.4GHZ
FULL-RANGE RADIO SYSTEM REV·
O· LU· TION· ARY —
constituting or bringing about a major
or fundamental change
by Scott Stoops
I hesitate to describe any RC product
using the term "revolutionary", but in
the case of the new Spektrum DX7, it is
the perfect word to describe a product
that has the potential to fundamentally
change the world of RC. Some may
think I am being overly dramatic, but I
suspect that after reading this article,
you just might agree with my take on
the Spektrum DX7.
DX7 2.4GHZ
FULL-RANGE RADIO SYSTEM REV·
O· LU· TION· ARY —
constituting or bringing about a major
or fundamental change
by Scott Stoops
I hesitate to describe any RC product
using the term "revolutionary", but in
the case of the new Spektrum DX7, it is
the perfect word to describe a product
that has the potential to fundamentally
change the world of RC. Some may
think I am being overly dramatic, but I
suspect that after reading this article,
you just might agree with my take on
the Spektrum DX7.
| In late 2005, Spektrum introduced the RC world to Digital Spectrum Modulation 2.4GHz technology (DSM) for park flyers and electric helicopters with the Spektrum DX6 transmitter and AR6000 DSM receiver (see Fly RC, March 2006). Together they offer the freedom of crystal-free, pin-free, interference-free performance for your small models. With the recent introduction of the DX7 transmitter and AR7000 receiver, Spektrum has made this same technology available to models of any size and speed. I’ve had the distinct honor of testing the new Spektrum DX7 in a wide variety of airplanes for the last few months, and the new DSM2 technology has absolutely blown me away during this time. I have flown everything from small park flyers to 35 percent gas giants with this radio, all without a single glitch. The DX7 link is so solid, it is uncanny. Gone are the inevitable twitches and dropouts we have taken for granted with 72MHz systems. Let’s take a look at DSM2 technology, the DX7 transmitter and AR7000 receiver, and how they promise to revolutionize the way you fly model airplanes of every size. |
| SYSTEM FEATURES • Full-range 2.4GHz DSM2 Spektrum System • Compatible with models of all size and speed including giant-scale and turbine jet • 20 model memory • Compatible with AR6000 and AR7000 receivers (AR7000 included) • DS821 sport digital servos • 1500mAh 9.6V NiMH battery and charger • 1100mAh 4.8V Flat NiMH receiver pack • Fully digital trims • Improved programming with more mixes and better interface • Innovative model match and Servo synchronization technology FEATURES • Sub trim • Travel adjust • Dual rates • Exponential • Servo reverse • Trainer system select • Throttle recovery • Input select (switch select-ability for aux 2 and gear) • Dual-rate switch select • Fail safe • Servo monitor AIRPLANE-SPECIFIC FEATURES • 3 wing types • Elevator to flap mix • Aileron to rudder mix • Flap system • Differential • Switch assignable programmable mixes (6) HELICOPTER-SPECIFIC FEATURES • 4 swashplate types • Swashplate mix • Throttle hold • Three 5-point throttle mix curves • Four 5-point mix pitch curves • Revolution mix • Gyro sensing • Switch assignable programmable mixes (3) |
| SPECS SPEKTRUM DX7 TRANSMITTER CHANNELS: 7 MODEL MEMORIES: 20 MODEL TYPE: Air/Heli MODULATION: DSM2 BATTERY: 1500mAh NiMH WEIGHT WITH BATTERY: 28.6 oz. CURRENT DRAIN: 330mAh AR7000 SIZE: 1x0.63x1.86 in., main; .7x0.25x0.99 in., satellite WEIGHT: .46 oz. (13g) ANTENNA LENGTH: 1.25 in. DS821 SPORT DIGITAL SERVOS SIZE: 1.50x0.94x1.47 in. WEIGHT: 1.5 oz. TORQUE: 72 oz.-in. @ 4.8V, 88 oz.-in. @ 6.0V SPEED: .19 sec/60 degrees @ 4.8V; .15 sec/60 degrees @ 6.0V |
| 2.4GHz REFRESHER What exactly is the big deal with this new 2.4GHz technology? How can it possibly be glitch-free, and how can I just “turn on” with total disregard for a frequency board? It all begins with the manner in which the 72MHz and 2.4GHZ (2400MHz) bands are regulated. As you are aware, traditional 72MHz systems share the frequency band with many users, and interference is a mere power switch away if another user activates his radio on your frequency. The FCC also allows high-power users to locate in-between the channels dedicated for RC use, which can cause interference. Normally, 72MHz works very well as our receivers are great at weeding through all the noise, but interference, whether man-made or as a result of onboard electronics, does happen. When the FCC and other international bodies got together to come up with the rules for the new 2.4GHz frequencies, they took an entirely different tact. Instead of a frequency free-for-all, they decided to require all 2.4 GHz capable devices to interface with each other, ensuring multiple users couldn’t occupy the same frequency concurrently. Now, as you turn on your new DX7, it scans all 80 channels in the band, finds two that are free, locks onto them, and begins transmitting. Your transmitter simply can’t interfere |
| with other systems, and other transmitters can’t interfere with your system. Finally, the DX7 is immune to traditional RF noise caused by ignition systems and onboard electronics because the “noise” they create is in a completely different frequency range. My experience has proven to me that the DX7 and its DSM2 modulation is the most secure, glitch-free radio system on the market today. |
The AR7000 dual receiver has two components. The main receiver body has the servo connector block, The smaller satellite receiver is attached with a six inch extension so that it “sees” a different RF environment. In use the antennas should be extended straight out of their respective receiver bodies and mounted 90 degrees opposed to each other. |
| DSM2 MODULATION Based on the success of the DX6 and its DSM technology, Spektrum incorporated the second- generation DSM2 modulation into the new DX7 system. In addition to significantly increasing the range of the system, they’ve also increased the system’s speed and resolution, dramatically improving signal processing and latency. The result is a radio system that responds to your inputs faster than any 72MHz system on the market. My personal experience mirrors this claim. As a cautious modeler, I slowly ramped up during testing from smaller park flyers to my larger gas-powered models. Each test model was flown back-to-back—first with my standard 72MHz system, followed by the DX7 with identical mixing, rates and expo. In each case, the model flown with the DX7/AR7000 combo responded every bit as quickly and precisely as my fastest 72MHz system. From my perspective, variations in system response and latency are emphasized during maneuvers that require highly stick-pattern driven inputs like the rolling harrier—and in |
several cases, my timing had to be accelerated to compensate for the responsiveness of the DX7
system.
system.
| TWO SETS OF EYES — THE AR7000 DSM2 RECEIVER The original AR6000 DSM receiver used two integral receivers, each individually and independently tuned to different unique channels to ensure that if one channel lost frames, the second would maintain a secure link between the model and radio. The new AR7000 DSM2 receiver takes that redundancy one step further. The AR7000 has a second “remote” receiver in addition to the main receiving unit on the receiver’s PC board. The remote satellite receiver is attached to the main receiver with a six-inch lead. |
As with the DX6, the DX7
bind button on the back of
the transmitter is used to key
a receiver to the transmitter
and for range testing by
reducing the transmitter
output.
bind button on the back of
the transmitter is used to key
a receiver to the transmitter
and for range testing by
reducing the transmitter
output.
The basic premise is
that two eyes are
better than one, and
when separated by a
short distance, the
receivers see slightly
different RF
environments that,
when combined, offer
a far greater level of
precision and
accuracy. Data from
both receivers is
processed by the
AR7000’s onboard
software, resulting in
the clearest RF
picture possible. This
innovation
dramatically improves
the system’s precision,
but more important, it
improves its range by
allowing it to be used
in virtually any size or
speed of model.
that two eyes are
better than one, and
when separated by a
short distance, the
receivers see slightly
different RF
environments that,
when combined, offer
a far greater level of
precision and
accuracy. Data from
both receivers is
processed by the
AR7000’s onboard
software, resulting in
the clearest RF
picture possible. This
innovation
dramatically improves
the system’s precision,
but more important, it
improves its range by
allowing it to be used
in virtually any size or
speed of model.
Installing the AR7000, like the AR6000, is very
straightforward. Simply mount the primary receiver
with foam tape or a foam wrap anywhere in the
fuselage, or in the case of a helicopter on the main
radio tray. Mount the remote receiver with either foam
tape or servo tape at least two inches from the
primary receiver’s antenna array. In a perfect world,
each receiver’s 1.25-inch antenna array would be
mounted perpendicular to the other. I’ve tried to
emulate this ideal, as well as tried much more casual
installations, without a noticeable difference in
performance. The receiver has slots for up to seven
servos, so for airplanes with multiple servos per
channel, you can use Y-harnesses, Matchboxes, or
an external unit like the Smart-Fly Power Expander. I’
ve successfully flown the AR7000 many times in my
10-servo, 35 percent Giles powered with a DA-100
gas engine, and I’m convinced that
straightforward. Simply mount the primary receiver
with foam tape or a foam wrap anywhere in the
fuselage, or in the case of a helicopter on the main
radio tray. Mount the remote receiver with either foam
tape or servo tape at least two inches from the
primary receiver’s antenna array. In a perfect world,
each receiver’s 1.25-inch antenna array would be
mounted perpendicular to the other. I’ve tried to
emulate this ideal, as well as tried much more casual
installations, without a noticeable difference in
performance. The receiver has slots for up to seven
servos, so for airplanes with multiple servos per
channel, you can use Y-harnesses, Matchboxes, or
an external unit like the Smart-Fly Power Expander. I’
ve successfully flown the AR7000 many times in my
10-servo, 35 percent Giles powered with a DA-100
gas engine, and I’m convinced that
The DX7 switches are conveniently
located and easy to access. The
helicopter version moves the three
position flight mode switch to the left
side.
located and easy to access. The
helicopter version moves the three
position flight mode switch to the left
side.
the AR7000 is capable of flying any model requiring seven or less channels, even including complex
giant-scale gas airplanes.
giant-scale gas airplanes.
| PROGRAMMING Just a sample of the numerous screens available. The DX7 programming menu tree is logical and easy to follow. |
INNOVATIVE FEATURES — MODEL MATCH AND
SERVO SYNCH
We’ve all done it, but only some of us will admit it.
You know exactly what I am talking about. That’s
right, taking off with the wrong model selected on our
computer radio, of course. Technology to the
rescue—with the DX7, this event is a thing of the
past. For those of you familiar with the DX6, you know
that each receiver is “bound” to an individual
transmitter. The process is quick and easy, and is a
primary feature of the DSM technology linking the
receiver with a specific transmitter identification code,
ensuring that the receiver responds to that
transmitter alone.
The DX7 takes binding one step further. When
binding an AR7000 receiver to your transmitter, the
receiver also remembers the specific airplane model
you have actively selected on the DX7. That receiver
will now only respond to the DX7 when that model is
selected and active. With the DX7, it is finally
impossible to fly with the wrong model selected in the
transmitter. This feature also works with the original
AR6000 receivers. In fact, while the AR6000 retains
its original restriction for park flyers and small electric
helicopters, all of the new features described here
also apply to the AR6000 when used with the DX7.
Servo Sync is the other major innovation
incorporated into the DX7. Traditional radios use a
very linear transmission methodology, simply running
sequentially from channel one through, in this case
with a seven-channel transmitter, channel seven.
This causes slight delays, depending on the type of
mixing used. For instance, on a larger dual elevator
servo model, it isn’t uncommon to use channel
selections that are far apart, for instance, channels
two and seven on your receiver. This can result in a
perceptible lag between the two surfaces during quick
or extreme deflections.
The DX7 eliminates this with a feature called servo
sync. Basically, the DX7 looks at the different mixes
selected, and re-synchronizes the data so that servos
that need to move together actually move together. A
good example of this is a 120-degree CCPM three-
servo head on a helicopter. The DX7 knows the head
type mixing selected, and sends all three head servos
the correct data at the same time. The result is as
precise a feel as I’ve ever experienced in any radio
system.
DX7 PROGRAMMING SPECIFICS
Clearly, the most compelling feature of the DX7
system is the fact that it offers the security, speed
and precision of spread spectrum technology to
models of all sizes, so it might be easy to overlook the
fact that the transmitter itself is a really nice, feature-
packed mid-level sport radio. So the question begs,
how capable is the transmitter? Based largely on the
new JR 7202, the Spektrum DX7 offers all of the
mixing and programming flexibility that the vast
majority of the modeling community could possibly
need or reasonably use. As I mentioned earlier, I’ve
flown the DX7 in a wide variety of airplanes. These
have included small park flyers, traditional .60 size
club models, and even my 35 percent
SERVO SYNCH
We’ve all done it, but only some of us will admit it.
You know exactly what I am talking about. That’s
right, taking off with the wrong model selected on our
computer radio, of course. Technology to the
rescue—with the DX7, this event is a thing of the
past. For those of you familiar with the DX6, you know
that each receiver is “bound” to an individual
transmitter. The process is quick and easy, and is a
primary feature of the DSM technology linking the
receiver with a specific transmitter identification code,
ensuring that the receiver responds to that
transmitter alone.
The DX7 takes binding one step further. When
binding an AR7000 receiver to your transmitter, the
receiver also remembers the specific airplane model
you have actively selected on the DX7. That receiver
will now only respond to the DX7 when that model is
selected and active. With the DX7, it is finally
impossible to fly with the wrong model selected in the
transmitter. This feature also works with the original
AR6000 receivers. In fact, while the AR6000 retains
its original restriction for park flyers and small electric
helicopters, all of the new features described here
also apply to the AR6000 when used with the DX7.
Servo Sync is the other major innovation
incorporated into the DX7. Traditional radios use a
very linear transmission methodology, simply running
sequentially from channel one through, in this case
with a seven-channel transmitter, channel seven.
This causes slight delays, depending on the type of
mixing used. For instance, on a larger dual elevator
servo model, it isn’t uncommon to use channel
selections that are far apart, for instance, channels
two and seven on your receiver. This can result in a
perceptible lag between the two surfaces during quick
or extreme deflections.
The DX7 eliminates this with a feature called servo
sync. Basically, the DX7 looks at the different mixes
selected, and re-synchronizes the data so that servos
that need to move together actually move together. A
good example of this is a 120-degree CCPM three-
servo head on a helicopter. The DX7 knows the head
type mixing selected, and sends all three head servos
the correct data at the same time. The result is as
precise a feel as I’ve ever experienced in any radio
system.
DX7 PROGRAMMING SPECIFICS
Clearly, the most compelling feature of the DX7
system is the fact that it offers the security, speed
and precision of spread spectrum technology to
models of all sizes, so it might be easy to overlook the
fact that the transmitter itself is a really nice, feature-
packed mid-level sport radio. So the question begs,
how capable is the transmitter? Based largely on the
new JR 7202, the Spektrum DX7 offers all of the
mixing and programming flexibility that the vast
majority of the modeling community could possibly
need or reasonably use. As I mentioned earlier, I’ve
flown the DX7 in a wide variety of airplanes. These
have included small park flyers, traditional .60 size
club models, and even my 35 percent
IMAC aerobat. In each case, I found the DX7 to be a capable radio that was not only easy to program,
but also very intuitive to operate.
but also very intuitive to operate.
The DX7 is available in two versions:
airplane and helicopter. Both share
identical programming options,
differing only in switch layout, so each
can fly helicopters and airplanes
equally well. The DX7 includes a
1500mAh pack, allowing up to six
hours of operation between
recharges, a substantial upgrade over
the DX6. The pilot interface is very
logical, using a toggle switch and
confirmation button along each side of
the large LCD display. Like the 7202,
there are two basic programming
menus: system setup mode and
function mode. System setup options
include model selection, head type for
helicopters, wing type for airplanes,
and other “administrative” functions;
function mode options include dual
rates, exponential, and both
helicopter and airplane appropriate
mixing options including three
(helicopter) to six (airplane)
programmable mixes. For more on the
programming capabilities of the DX7,
take a look at the December 2006
issue of Fly
airplane and helicopter. Both share
identical programming options,
differing only in switch layout, so each
can fly helicopters and airplanes
equally well. The DX7 includes a
1500mAh pack, allowing up to six
hours of operation between
recharges, a substantial upgrade over
the DX6. The pilot interface is very
logical, using a toggle switch and
confirmation button along each side of
the large LCD display. Like the 7202,
there are two basic programming
menus: system setup mode and
function mode. System setup options
include model selection, head type for
helicopters, wing type for airplanes,
and other “administrative” functions;
function mode options include dual
rates, exponential, and both
helicopter and airplane appropriate
mixing options including three
(helicopter) to six (airplane)
programmable mixes. For more on the
programming capabilities of the DX7,
take a look at the December 2006
issue of Fly
Here is a typical AR7000 installation for a giant scale model.
I located the satellite receiver up on the bulkhead with a little
double-sided foam tape. The SmartFly power expander
distributes signal and regulated power to the various
servos.
I located the satellite receiver up on the bulkhead with a little
double-sided foam tape. The SmartFly power expander
distributes signal and regulated power to the various
servos.
RC for my review of JR 7202. Other than broadcasting on different frequency bands, the radios, for
all intents and purposes, are the same.
all intents and purposes, are the same.
Overall, the DX7 offers a very capable
radio system that when combined with
the AR7000 full-range receiver will
meet the needs of the vast majority of
modelers, all in a glitch-free and
affordable package.
CONCLUSION
In my 23 years of RC modeling, I’ve
seen technology that claimed to be the
next great thing come and go many
times over. Some products, however,
make their mark in such a way that
they completely redefine the market. I
would offer that the Spektrum DX7,
with its 2.4GHz full-range DSM2
technology, is such a product. After
operating the DX7 for the last few
months, I’m completely sold on the
DX7—not one single glitch in well over
150 flights. The confidence of knowing
that you can’t be
radio system that when combined with
the AR7000 full-range receiver will
meet the needs of the vast majority of
modelers, all in a glitch-free and
affordable package.
CONCLUSION
In my 23 years of RC modeling, I’ve
seen technology that claimed to be the
next great thing come and go many
times over. Some products, however,
make their mark in such a way that
they completely redefine the market. I
would offer that the Spektrum DX7,
with its 2.4GHz full-range DSM2
technology, is such a product. After
operating the DX7 for the last few
months, I’m completely sold on the
DX7—not one single glitch in well over
150 flights. The confidence of knowing
that you can’t be
The DX7 transmitter antenna hinges 90 degrees and can
be rotated to either side for compact storage.
be rotated to either side for compact storage.
“shot-down” by an errant signal is hard to put a value on. For my peace of mind though, at $349.99,
the DX7 is an absolute steal.
the DX7 is an absolute steal.
Links
Spektrum, distributed by Horizon Hobby, www.spektrumrc.com, (800) 338-4639
Spektrum, distributed by Horizon Hobby, www.spektrumrc.com, (800) 338-4639