Operating instructions

DMD20/DMD20 LBST Universal Satellite Modem User Interfaces
TM103 – Rev. 2.8 4-47
LOOPBACK WITH ETHERNET DATA INTERFACE
Usage of the modems loopback capabilities in conjunction with the Ethernet data
interface can produce undesirable network loops. In order to run any type of data test
with an Ethernet interface
y
ou must utilize two modems connected back to back. Simpl
y
using one modem and a loopback will not produce the desired results.
LOOPBACK {IF, TERR TX/RX, BASEBAND TX/RX, NONE,
TERR RX, BASEBAND RX, TERR TX, BASEBAND TX,
IFEC TX}
Terrestrial Loopback is performed at the Terrestrial
Interface
IF: IF loopback loops the IF output of the Modulator to
the IF input of the Demodulator. If using 8PSK or
16QAM Modulation, the output power must be above
-15 dB.
TERR TX/RX: Enables both. Baseband loopback is
performed at interface between the Baseband Processor
Card and the Modem Card. This ensures
Framer/Deframer integrity.
BASEBAND TX/RX: Enables both Baseband Tx and
Baseband Rx.
NONE: No loopback performed.
TERR RX: (Distant Loop) Sends received satellite data
to the Modulator for transmission to the distant end.
BASEBAND RX: Sends Rx data from the Modem Card
to the Tx data input to the Modem Card.
TERR TX: Sends Tx Terrestrial Data to Rx data out.
BASEBAND TX: Sends Tx data to the receive input to
the BB Card.
CARRIER TYPE {NORMAL, CW, DUAL, OFFSET, POS FIR, NEG FIR}
Allows the user to set the type of carrier.
NORMAL: Causes the Modulator to output normal
modulation.
CW: Causes the Modulator to output a pure carrier.
DUAL: Causes a double sideband output.
OFFSET: Causes a single sideband output.