I-25
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:
Q: Which do I turn on first, the transmitter or the receiver?
A: It doesn’t matter. If the receiver is turned on first, the receiver
starts scanning the band looking for a signal with its pre-bound
GUID. At this time no servo output pulses are present and 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
finds the GUID (Globally Unique Identifier code) stored during
binding. The system then connects and operates normally.
If the transmitter is turned on first, the transmitter scans the 2.4
GHz band and acquires two open channels. When the receiver is
then turned on, the receiver scans the 2.4GHz band looking for
the previously stored GUID; 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.
Q: Sometimes the system takes longer to connect and
sometimes it doesn’t connect at all - why?
A: In order for the system to connect (after the receiver is
bound), it must receive a large number of continuous (one after
the other) uninterrupted perfect packets from the transmitter.
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 can 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;
should a loss of signal occur (failsafe), the system connects
immediately (4ms) when the signal is regained.
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 10 volts. With most systems this is not a problem as, in fact,
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, thus 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 I-26 as this explains how to test for and prevent this
occurrence. Note the JR R1221 and newly manufactured JR and
Spektrum DSM receivers have a new QuickConnect feature that,
if a temporary power loss occurs, will reconnect the system in
less than .25 seconds. If a power loss or brownout occurs, the
receiver will indicate the power loss by flashing. If you land and
the receiver is flashing, it’s important that you investigate and
correct the issue that caused the power loss.
Q: Sometimes my receiver loses its bind and won’t connect,
requiring rebinding. What happens if the bind is lost in flight?
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:
Summary of Contents for JR DSM 12X
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