There are two primary types of 2.4GHz spread spectrum technology
used in RC—Frequency Hopping Spread Spectrum (FHSS) and
Direct Sequence Spread Spectrum (DSSS).
Originally, Spektrum engineers started their development with
FHSS-based systems because they are relatively easy and inexpensive
to develop. However, it was soon discovered that FHSS had certain
limitations that would prevent it being the optimal solution
for RC. While more difficult and costly to develop, Spektrum
chose to pursue a DSSS-based solution. The result was the patented
DSM technology used in all of Spektrum’s RC systems.
Besides solving critical response and re-link issues, DSM also
provides more processing gain for superior range. And as more
and more Spektrum users have been appearing at indoor flying
events where numerous wireless routers and other 2.4GHz RC systems
are in use, they’ve discovered yet another big benefit.
Namely that as the 2.4GHz noise floor rises (more 2.4GHz units
are turned on), they don’t experience any reduction in
response time. The DSSS-based technology keeps latency at an
absolute minimum no matter how busy the 2.4GHz environment gets. |
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SmartSafe deals subtly differently with two safety critical scenarios,
one of which is especially important for electric powered
planes. Fail-safe settings are established during the binding
process at the positions of the sticks, usually low throttle
and neutral on other channels.
The first scenario is that the receiver is turned on without
a signal from the transmitter. In this event all of the channels
go to the fail-safe positions set during the binding process
but the receiver doesn’t send any signals out on the throttle
channel, so the speed controller cannot arm and start the motor.
Once the transmitter is turned on and an RF link is established
the receiver will send out a low throttle signal and arm the
speed controller once the stick is positioned at low throttle.
From that point it functions, as do the other channels, as normal.
The second case scenario is that the signal is lost whilst both
transmitter and receiver have an established RF link. In this
event, as unlikely as it is, SmartSafe will take the throttle
channel to its setting programmed during the binding process,
while all other channels stay at last position held.
Aeroplanes are a little more complicated when it comes to
retaining a solid RF link to than surface bound craft because
they manoeuvre in three dimensions. Surface craft like boats
and cars are fixed in one plane so orientation to the receiver’s
aerial, while it’s pointing at the sky as it should,
remains constant ruling out signal fade, a condition that
reduces range. To solve just that problem with aeroplanes
Spektrum employs the use of two separate radio channels and
receivers, each with its own aerial. The radio transmits
the signal on both frequencies simultaneously and because
the two aerials have different
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orientation should one of
those signals be lost, for even milliseconds, due to its orientation
to the transmitter the other one will still be on-line. The
net result is no loss of signal, no interruption, no dropouts,
no problems. A solid RF link is there all the time.
DX6i features DSM2™, which is second generation DSM.
DSM2 provides all the benefits of DSM but with the added
bonus of doing it faster. By processing the signal faster
than any PCM radio system available today and at 1024 bit
resolution the link that connects pilot and plane is sharpened
making him feel more in contact and control of his plane.
It’s not uncommon to forget to check that the model that
is about to take off is the one that’s profiled in the
transmitter display. The consequences can be disastrous though.
Once again Spektrum redefines flight safety with ModelMatch
by making this kind of error a thing of the past. With DX6i
a profile code is embedded into the receiver and if it doesn’t
match the one embedded in the signal, indicated by the model
name on the display, the model’s controls simply won’t
A new feature on DX6i that re-sequences the bits of data based
on the type of mixing selected. So if dual elevators or 3-servo
CCPM has been set-up ServoSync will see to it that those
servos are performance optimised by receiving their impulses
together. This results in a more positive feel to control
input.respond.
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