CDM-625A Advanced Satellite Modem MN-CDM625A
Appendix M Revision 4
M–9
For the example shown, the latency for a 16k block DVB-S2 ACM scheme is
approximately 7 times higher than VersaFEC ACM.
• The latency for a 64k block DVB-S2 ACM scheme is approximately 25 times
higher than VersaFEC ACM.
M.6.2 Configuring VersaFEC ACM in the CDM-625A
VersaFEC ACM requires the appropriate FAST code for the maximum operating
symbol rate.
Chapter 6. FRONT PANEL OPERATION.
Do these steps to configure the CDM-625A for VersaFEC ACM operation from the CDM-625A
front panel:
Set the Tx and Rx modes as IP-ACM.
Mode:Tx=IP-ACM:None Rx=IP-ACM:None
(422,V35,G703s,Audio,LVDS,HSSI,IP,ASI)
(SELECT) CONFIG: TX SYMB
Enter the desired transmit symbol rate. Note that
this is a fundamental departure from the way in
which the modem is typically configured.
Tx-IF Freq Power FEC Mod Symb Scrambler
(Data 00192.000kbps, 00131.657ksps)()
TxSymbolRate = 01000.000 ksps (ACM Mode)
Data Invert=Off Clock Invert=Off ()
The Transmit symbol rate is limited by the FAST code installed. There are three options:
• 37 ksps to 300 ksps • 37 ksps to 1200 ksps • 37 ksps to 4100 ksps
(SELECT) CONFIG: TX POWER
If Manual mode is selected, enter the desired
transmit output level. This will also be the Nominal
Power value if AUPC is selected.
Output Power: Mode= Manual (Manual, AUPC)
Level= –20.0 dBm ()
If AUPC mode is selected, two additional choices
are presented – Mode/Range and Alarm Action,
Output Power: Mode= AUPC (Manual, AUPC)
Mode/range Alarm Action ()
In all case except MEO (which is a very unusual
mode) the mode is fixed at Normal. Enter the
maximum permitted power increase, between 0.0
AUPC-ACM Mode = Normal (Normal, +/- Track)
Max Permitted Power Increase: 3.0 dB ()
You can chose to generate an alarm when the max
power or min ModCod has been reached, or not at
all. You can also chose what happens to Tx Power
when the remote demod unlocks. The choices are
Nominal Power, Max Power, or Hold.
Tx Alarm: None (MaxPwr, MinMCod, None)
Rem Dmod Unlock Act=Nom Pwr(Nom, Max, Hold)
(SELECT) CONFIG: RX SYMB
Enter the desired receive symbol rate. Note that
asymmetric operation is supported – transmit and
receive symbol rates do not have to be equal.
RxIF Freq FEC Demod Symb Descram Eq EbNo
(Data 02048.000kbps,02184.533ksps)()
RxSymbolRate = 01000.000 ksps (ACM Mode)
Data Invert=Off Clock Invert=Off ()
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