Spektrum SPMMSJR9 - Manual (Page 13)

Spektrum Air Module 1
In helicopters, there is generally enough room on the servo tray to achieve the
necessary separation. If necessary, a mount can be made using clear plastic to
mount the remote antenna as shown below.
Installing the AR9000
The AR9000 incorporates dual internal receivers, and one or two remote receivers
offering the security of up to four simultaneous RF links for the ultimate in multi-
path RF security. Two internal receivers are located on the main PC board, while
a third remote receiver must be plugged into one of the antenna ports in order for
the system to operate. Optionally, a second remote antenna can be plugged into
the remaining remote antenna port giving a total of four operational receivers. By
locating these receivers in different locations throughout the aircraft, each receiver
is exposed to its own RF environment, greatly improving path diversity (the ability
of the receiver to see the signal in all conditions).
Installing the Receiver