SPEKTRUM DX7 • INTRODUCTION
Tips on Using 2.4GHz Systems
While your DSM equipped 2.4GHz system is intuitive to operate, functioning nearly identically to 72MHz
systems, following are a few common questions from customers.
1. Q: Which do I turn on rst, the transmitter or the receiver?
A: If the receiver is turned on first (except for the AR500, AR6100 and the AR7100 receivers), all servos except
for the throttle will be driven to their preset failsafe positions set during binding. At this time, the throttle
channel doesn’t put out a pulse position preventing the arming of electronic speed controllers or, in the case
of an engine-powered aircraft, the throttle servo remains in its current position. When the transmitter is then
turned on, the transmitter scans the 2.4GHz band and acquires two open channels. Then the receiver that was
previously bound to the transmitter scans the band and finds the GUID (Globally Unique Identifier code) stored
during binding. The system then connects and operates normally.
Note: When using the AR500, AR6100 or the AR7100, if the receiver is turned on first, no output
pulses are sent to any channels.
If the transmitter is turned on first, the transmitter scans the 2.4GHz band and acquires two open channels. When
the receiver (except forAR500, AR6100 and AR7100 receivers) is then turned on for a short period (the time it
takes to connect), all servos except for the throttle are driven to their preset failsafe positions while the throttle
has no output pulse. The receiver scans the 2.4GHz band looking for the previously stored GUID, and when it
locates the specific GUID code and confirms uncorrupted repeatable packet information, the system connects
and normal operation takes place. Typically this takes 2 to 6 seconds.
2. Q: Sometimes the system takes longer to connect and sometimes it doesn’t connect at all?
A: In order for the system to connect (after the receiver is bound) the receiver must receive a large number of
continuous (one after the other) uninterrupted perfect packets from the transmitter in order to connect. This
process is purposely critical of the environment, ensuring that it’s safe to fly when the system does connect.
If the transmitter is too close to the receiver (less that 4 feet) or if the transmitter is located near metal objects
(metal transmitter case, the bed of a truck, the top of a metal work bench, etc.) connection will take longer, and
in some cases, connection will not occur as the system is receiving reflected 2.4GHz energy from itself and is
interpreting this as unfriendly noise. Moving the system away from metal objects or moving the transmitter away
from the receiver and powering the system up again will cause a connection to occur. This only happens during
the initial connection. Once connected, the system is locked-in and, should a loss of signal occur (failsafe), the
system connects immediately (4ms) when signal is regained.
3. Q: I’ve heard that the DSM system is less tolerant of low voltage. Is that correct?
A: All DSM receivers have an operational voltage range of 3.5 to 9 volts. With most systems, this is not a
problem as most servos cease to operate at around 3.8 volts. When using multiple high current draw servos
with a single or inadequate battery/power source, heavy momentary loads can cause the voltage to dip below
this 3.5-volt threshold, causing the entire system (servos and receiver) to brown out. When the voltage drops
below the low voltage threshold (3.5 volts), the DSM receiver must reboot (go through the start-up process of
scanning the band and finding the transmitter) and this can take several seconds. Please read the receiver power
requirement on page 24 as this explains how to test for and prevent this occurrence.
Tips on Using 2.4GHz Systems (continued)
4. Q: Sometimes my receiver loses its bind and won’t connect, requiring rebinding. What
happens if the bind is lost in ight?
A: The receiver will never lose its bind unless it’s instructed to. It’s important to understand that during the
binding process the receiver not only learns the GUID (code) of the transmitter but the transmitter learns and
stores the type of receiver that it’s bound to. If the bind button on the transmitter is pressed at any time and the
transmitter is turned on, the transmitter looks for the binding protocol signal from a receiver. If no signal is
present, the transmitter no longer has the correct information to connect to a specific receiver and in essence
the transmitter has been “unbound” from the receiver. We’ve had several customers that use transmitter stands
or trays that unknowingly depress the bind button and the system is then turned on, losing the necessary
information to allow the connection to take place. We’ve also had customers that didn’t fully understand the
range test process and pushed the bind button before turning on the transmitter, also causing the system to
“lose its bind.” If, when turning on, the system fails to connect, one of the following has occurred:
• The wrong model has been selected in the model memory (ModelMatch).
• The transmitter is near conductive material (transmitter case, truck bed, etc.) and the reected 2.4GHz energy
is preventing the system from connecting (see #2 above).
• The bind button was unknowingly (or knowingly) depressed and the transmitter was turned on previously,
causing the transmitter to no longer recognize the receiver.
5. Q: Can I use a 3-cell Li-Po pack in my transmitter?
A: No. All current JR and Spektrum transmitters are designed to operate using a 9.6-volt transmitter pack. A fully
charged 3-cell Li-Po pack puts out 12.6 volts. This higher voltage can overload the power-regulating transistor
causing damage and or failure, possibly in flight. Many of our customers have experienced failures using 3-cell
Li-Po packs and their use in JR and Spektrum transmitters is highly advised against. The X9303 2.4 system will
operate for over 15 hours using a 2700mAh Ni-MH battery.
6. Q: How important is it that I test my system using the Spektrum Flight Log?
A: For most sport airplanes and helicopters, the use of the Flight Log is unnecessary. For sophisticated aircraft,
especially those that have significant conductive materials within the airframe (e.g., jets, scale airplanes, etc.),
the Flight Log offers an extra measure of confidence that all radio components are working optimally. The Flight
Log is an important tool that allows the confirmation that the installation (position of the internal and remote
receivers relative to the conductive materials in the aircraft) is optimized and that the RF (radio) link is operating
at the highest levels of performance.
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