Comtech EF Data CDD-880, Инструкция по установке и эксплуатации

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CDD-880 Multi Receiver Router MN-CDD880
Ethernet-based Remote Product Management Revision 2
6–40
Input Port Status
This section summarizes the operating status of the demod ports. From left to right:
Column Description
Demod # This is the available ”filled” demodulator slot (automatically assigned in pairs per
each installed dual demodulator card).
Lock This displays the status of the VersaFEC decoder as Locked, Unlocked or Disabled.
Eb/No (dB) This is the estimated channel noise level.
Estimated Corrected BER This is the B it E rror R ate after VersaFEC decoding.
RSSI (dB)* This is the R elative S ignal S trength I ndicator (0 – 60 dB of demod operating range).
Rx Freq Offset (Hz) This is the estimated offset from demod configured frequency (in Hz).
Circuit ID This displays the identification label assigned to the individual demodulator.
About CDD-880 RSSI (Receive Signal Strength Indicator): The traditional method of
reporting the input signal strength is the RSL (Receive Signal Level). Comtech EF Data
modems are specified to meet BER requirements when the
RSL_min = -130 +
10
log
(Symbol Rate). The maximum performance (due to AGC) is
RSL_max =
R 50 dB
.
In order to calculate the expected RSL, you must then know the current Symbol Rate
and use these conversion formulae.
The CDD-880 is designed differently from most other Comtech EF Data products
because it has to accommodate the energy from 12 channels at the front end. There
are several analog and digital AGCs throughout the signal chain; because of this, the
RSSI is a relative measure of received power, as opposed to absolute power. The
CDD-880 reports a symbol rate-independent RSSI, which greatly simplifies operation.
The CDD-880 is designed to operate as per the specified BER performance for any
value of RSSI greater than 0. If the RSSI is negative, then the demodulator may not
perform as intended.
Due to link fading and impairment, Comtech EF Data recommends that, during Clear
Sky commissioning, you configure the target RSSI as follows:
RSSI clear sky > Max Fade Depth + Margin
(where the recommended margin is ~3 to 4 dB).
For example: If the Max Fade Depth = 10 dB, then the Clear Sky RSSI should be ~14.
Note that the CDD-880 is designed to report both the RSL and RSSI.
Events
The ‘STORED EVENT’ LED provided on the Virtual Front Panel lights amber to indicate
the presence of any stored event(s) or alarm(s).