Spektrum SPMAR8000 - Manual (Page 9)

EN
Tips on Using Spektrum 2.4GHz
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: If the receiver is turned off first—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 output a pulse
position preventing the arming of electronic speed controllers or in the case of an engine powered
aircraft the throttle servo remaining 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.
If the transmitter is turned on first—the transmitter scans the 2.4GHz band and acquires two
open channels. When the receiver 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.
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 consecutive 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 than 4 feet) or if the
transmitter is located near metal objects (metal TX 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 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.
Q: I’ve heard that the DSM system is less tolerant of low voltage. Is this correct?
A: All DSM receivers have an operational voltage range of 3.5 to 9.6 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 section as this explains how to test for and prevent this
occurrence.
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 transmitter is placed
into bind mode, 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
DX7 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 DX7 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.”