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English
4. OPERATING INSTRUCTIONS
4.1 Dimensioning a Fibre Optic system
The optic system attenuation of the system must range between 15 and 21dB. Refer to the technical features of passive
components included in the distribution to calculate the optic system attenuation.
The OPT-RX SCD2guarantees a suitable level of the TV and SAT signal at the DCSS output if the optic system attenuation
between the transmitter and the receiver is 15 ÷ 21 dB and the RF signal in the OPT-TX DT input follows the indications given in
the transmitter manual
ATTENTION:
•
Don’t connect the OPT-TX DT and the OPT-RX SCD2 directly, unless proper line optic attenuators are used.
•
it is essential to use an optic meter to check the optic level in the receiver and avoid to damage the receiving photodiode (it
might be damaged if the input signal is higher than -8dBm).
4.2 Output levels to the optical receiver
SAT
The SAT power in the DCSS outputs of the OPT-RX SCD2 optic receiver is 82dbuV if both the optic input level and the correct
dimensioning of the optic system attenuation are met.
TV
The output TV level from the OPT-RX SCD2UK fibre optic receivers depends on the number of the channels transmitted by the
transmitter and the optic attenuation of the stand. Please remember that 1dB of optic loss corresponds to 2dB of attenuation at
electric level (RF).
The following are a few reference levels of the TV (DVB-T/CATV) signals at the receiver output:
RF output level per MUX
No. of Muxes
Receiver optical Input -8dBm
Receiver optical Input -14dBm
40
87dBµV
75dBµV
16
91dBµV
79dBµV
8
94dBµV
82dBµV
4
97dBµV
85dBµV
Table 2: Indication of the output levels in OPT-RX SCD2 - TV signal
NOTE: 1dB optic signal corresponds to 2dB at electric level (RF).
FM, DAB and DVB-T
The FM and DAB signal levels must be 10dB lower than DVB-T.
OPT-RX 4 MINI
Shown below are some of the reference levels of the signals output to the receiver OPT-RX 4 MINI:
TV (DVB-T/CATV)
The overall output power is -27dBm (82dBµV) with 21dB of optical attenuation which means that the fewer multiplexes that are
transmitted, the better the output level and quality.
The FM and DAB signal levels must be 10dB lower than DVB-T.
5. TYPICAL INSTALLATION EXAMPLES
Some example diagrams are available at the end of the manual and on the website www.fracarro.com