Comtech EF Data CDM-425, Installation And Operation Manual

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CDM-425 Advanced Satellite Modem
Revision 0
Introduction 1–19 MN-CDM-425
1.4.2 Demodulator
Note: Data rate range, operating modes, descrambling, input impedance/return loss etc, as per
Sect. 1.4.1 Modulator .
Input power range, desired
carrier
950-2250 MHz band:
-130 + 10
log
(symbol rate) to -80 + 10
log
(symbol rate) dBm
50-180 MHz band:
-105 + 10
log
(symbol rate) to -70 + 10
log
(symbol rate) dBm
Maximum Composite
Operating Level
950-2250 MHz band:
102 – 10
log
(symbol rate, desired carrier) dBC, +10 dBm max, with the additional requirement that
within ±10 MHz of the desired carrier, composite power is ≤ +30 dBC.
50-180 MHz band:
94 – 10
log
(symbol rate, desired carrier) dBC, +10 dBm max, with the additional requirement that
within ±10 MHz of the desired carrier, composite power is ≤ +30 dBc
Absolute Maximum, No
Damage
+20 dBm
FEC VersaFEC: 6 bit soft decision, proprietary
VersaFEC-2: 8 bit soft decision, proprietary
Acquisition range Programmable in 1kHz increments, and subject to the following:
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 ±300 kHz
Acquisition time Highly dependent on data rate, FEC rate, and demodulator acquisition range.
Examples: 120 ms average at 64 kbps, R1/2 QPSK, ±10 kHz acquisition sweep range, 6dB
Eb/No
2 s average at 18 kbps, R1/2 QPSK, ±10 kHz, 6dB Eb/No
Clock tracking range ±100 ppm min
Clocking modes Full range of clocking options supported – see plesiochronous/Doppler buffer section
LNB 10 MHz Reference
On center conductor of L-Band input connector, selectable ON/OFF. Level: -3dBm
±
3 dB.
Source: either Internal modem reference or External reference
Performance: For phase noise, refer to L-Band modulator 10 MHz. Frequency stability same as
the modulator 10 MHz reference.
LNB Voltage On center conductor of L-Band input connector, selectable ON/OFF, 13, 18VDC at 500 mA
maximum.