Advantech AMT-70, Installation And Operation Manual, Page: 58 / 160

AMT-70/AMT-73/AMT-75 Installation and Operation
If these loop-back components are not readily available, you could use the internal IF loop-back mode
of the modem. To activate the internal IF loop-back mode, perform the following:
From the MAIN MENU, arrow to TEST, hit ENT.
With the M of MODE flashing, hit ENT
Arrow to LOOPBACK, select ON, and hit ENT.
From the MAIN MENU, arrow to RX, hit ENT.
Arrow down to INPUT, hit ENT.
Select LOOPBACK and hit ENT
This is an absolute BER test capability that provides accurate results. To review the results, perform
the following:
From the MAIN MENU (if in a different menu, hit CLR once or twice to get back to the MAIN
MENU), arrow over to MONITOR and hit ENT.
Arrow over to RX and hit ENT.
Arrow down several times until BER appears in the upper left corner of the display. It will
display unlocked
while the modem is acquiring the signal.
It may be necessary to raise the power output to get the modem to acquire. To do this, perform the
following steps:
From the MAIN MENU, arrow over to TX and hit ENT.
Hit ENT when the T in TX flashes.
Arrow down (twice) until POWER = -xx dBm appears (xx should actually be -25 at this time).
Arrow over until the P in POWER is flashing. Hit ENT.
Change the power output by arrowing over to each value and then use the keypad to enter the
number. When the number is correct, hit ENT, and the new value entered will be executed.
Once the demodulator locks up, the BER readout will display the actual number of accumulated errors.
(You must be in MONITOR MAIN MENU and BER, as above.) Other estimated values, such as SNR,
Eb/No, baud (symbol) rate, AGC (labeled POWER.AGC) can be observed during this BER testing by
arrowing up or down while in the MONITOR menu.
If a different data rate, code rate, FEC type, or modulation scheme is desired, use the information from
Figure 6 to change those parameters:
Figure 9: Parameter Changes in Test Mode
TX Main Menu RX Main Menu
PARAMETER CURRENT
VALUE
DESIRED
VALUE
PARAMETER CURRENT
VALUE
DESIRED
VALUE
MOD QPSK 16QAM DEMOD QPSK 16QAM
UNITS BPS BPS UNITS BPS BPS
CARR FRQ 1000000000Hz 0950000000Hz CARR FRQ 1000000000Hz 0950000000Hz
DATA 005000000BPS 2048000BPS DATA 005000000BPS 2048000BPS
CODE INTELSAT TPC16K CODE INTELSAT TPC16K
RATE ½ 8/9 RATE 1/2 8/9
RSRATE OFF OFF RSRATE OFF OFF
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ENTER the changed values from the TX and RX menus, then page down to RECONFIGURE =
READY, press enter and then enter again to CONFIRM.