Advantech AMT-70, Installation And Operation Manual, Page: 44 / 160

AMT-70/AMT-73/AMT-75 Installation and Operation
mode from the RS-485 port.
Alternatively, a Packet Protocol mode can be selected. This is recommended for use by
programmers in the development of a Network Management System (NMS) or perhaps when
the modem is to be used in a bandwidth-on-demand system. The Packet Protocol speeds up
the set-up time of a modem or a series of modems. Refer to
Paragraph 7.3
for more
information regarding Packet Protocol.
10/100BaseT Ethernet Port
– There are two 10/100BaseT Ethernet M&C ports on the rear
panel. One port (RJ-45), nearest to the power connector (P1 for AMT-70; J10 for AMT-73L) is
used during manufacturing purposes only, and is not intended for use in the field. The other
port (RJ-45), furthest from the power connector (P6 for AMT-70, J9 for AMT-73L) provides full
capabilities to all functions of the modem, with the same instruction set as is available to the
RS-232 and RS-485 M&C ports.
This port supports SNMP V2 (Simple Network Management Protocol, Version 2) and Telnet.
Setup of the network IP address and the subnet mask can be performed from the active front
panel (
Paragraph 4.2.5.5
) or the RS-232 serial M&C port (
Paragraph 5.9
).
Using Telnet in the terminal emulation mode for remote management is described in
Paragraph 5.10.3
.
3.2
Acquisition, FEC, Modulation, and Eb/No
3.2.1
Demodulator Acquisition Tips
This section is a useful checklist for debugging the demodulator acquisition process, with some tips for
getting the best performance from the modem.
Check the input connection. The L-Band connection must be connected to the correct input
and the correct input selected under software control. Input 1 is closest to the Ethernet
connector.
Check the LNB control signals. DC power (and therefore polarity selection), 22 kHz switching
tone and 10MHz reference are switched off by default.
Check the L-Band frequency.
Check the demodulator configuration. The spectrum sense may be true or inverted. The
symbol rate, alpha, modulation and coding must be correctly configured. The frequency
acquisition range must be correctly configured – this is described below.
Use the “
rstatus details
” command to verify that the demodulator has acquired2.
The frequency acquisition range is dependant on symbol rate, the use of FFT assistance and use of
the frequency sweep.
As a basic rule without FFT assistance the frequency acquisition range can be assumed to be 2% of
symbol rate for QPSK and 1% for 8PSK.
If Spectral Analysis (FFT assistance) is enabled – use command
rspanl
- then the acquisition range for
all modulation types can be assumed to be 10% of Symbol rate. For example at 64 kSymbol
acquisition would be +/- 7kHz. To increase the acquisition range it is possible to set a frequency sweep
using the
rsweep
(sweep range) and
rssize
(step size).
44
2
The front panel LED also indicates if the modulator is locked.