Comtech EF Data CDM-625 - Manual (Page 138)

CDM-625 Advanced Satellite Modem Revision 15
Front Panel Operation MN-CDM625
5–38
• APC,Side B,C-band • APC,Side B,X-band • APC,Side B,Ku-band
• APC,Side B,Ka-band
With no CnC module (card) installed, CnC Mode is ‘ Off’, this menu is inaccessible, and the
CONFIG: CnC → Mode screen appears as shown:
CnC Mode: Off (Off, On, APC)
Card not installed ()
5.2.1.8.2 CONFIG: CnC  CONFIG: CnC  Freq-Offset
CnC Frequency Offset: (range 1-032)
+/-015 kHz ()
Use this menu to enter the maximum expected frequency offset between the outbound
interferer and the desired inbound. It normally corresponds to the demod acquisition range.
Use the ▲▼ arrow keys to edit the CnC Frequency Offset value, and then press ENTER. The
upper limit of Frequency Offset is determined by the Rx symbol rate:
• Below 64 ksymbols/sec: ±1 to ±(Rs/2) kHz , where:
Rs=symbol rate in ksymbols/sec
• Between 64 and 389 ksymbols/sec: ± 1 up to a maximum of ± 32kHz
• Above 389 ksymbols/sec: ±1 to ± (0.1Rs) kHz, up to a maximum of ± 200 kHz
This range is pre-calculated and displayed in parentheses for reference.
5.2.1.8.3 CONFIG: CnC  Search-Delay
CnC Search Delay: (range 0-330ms)
Min: 010 ms Max: 290 ms ()
To reduce the time taken for the CnC algorithm to converge, you may apply restrictions to the
range of delay used by the search. During initial link testing, it should be set to 240 ms (min) and
300 ms (max). Once CnC has found the exact delay, the value can be further reduced but care
should be taken to allow sufficient range to accommodate changes in path delay due to
Doppler.
If CnC is being bench-tested with two units in a back-to-back configuration, the
minimum delay should be set to 0 ms, and the maximum to 20 ms. This takes into
account the lack of satellite delay.