User's Manual
SATELLINE-4Pro
User Guide v0.93 DRAFT
23
7.2 Receiver
The sensitivity of the receiver depends on the channel spacing of the radio modem (=data speed
of the radio interface) and on the mode of the FEC (error correction) according to the table below
(BER 10E-3):
12.5 kHz
25 kHz
4FSK
FEC OFF
-115 dBm
-112 dBm
4FSK
FEC ON
-117 dBm
-116 dBm
8FSK
FEC OFF
-107 dBm
-103 dBm
8FSK
FEC ON
-115 dBm
-114 dBm
16FSK
FEC ON
-108
dBm
-106
dBm
The Signal Threshold Level setting of the receiver determines a level, above which the search for
the actual data transfer signal is active. It is recommended that values given in the table are used.
If the Signal Threshold Level setting is set too low (the CD-LED is ON constantly), it is possible that
the receiver is trying to synchronise itself with noise, in which case, the actual data transmission
might remain unnoticed. Alternatively, weak data transmissions will be rejected, even though they
would be otherwise acceptable.
7.3 Priority RX/TX
SATELLINE-4Pro offers a Priority setting, which selects the priority between reception and
transmission. The setting can be changed in Programming Mode. By default, transmission has
higher priority than reception i.e. the default value is Priority TX.
Priority TX means that a terminal device attached to a radio modem decides the timing of the
transmission. The transmitter is immediately switched on when the terminal device starts to output
data. Should reception be in progress, the radio modem will stop it and change to a transmit state.
There is no need to use any handshaking for the control of timing.
Priority RX means that a radio modem tries to receive all data currently in the air. If a terminal
outputs data to be transmitted (or an SL command) it will buffered. The radio modem will wait until
the reception has stopped before transmitting the buffered data. This will result in timing slacks to
the system, but decreases the number of collisions on the air; this is particularly useful in systems
based on multiple random accesses.
If the Repeater Function has been set on, priority setting is automatically switched to RX mode.