Televes DTT, Руководство пользователя

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User manual DTT Channel Processor
5.3.- Setting-up recommendations for a
correct headend installation.
- Use a preamplifier if the input level to the
channel processors is low (below 57
dBµV). Otherwise the C/N of the digital
channel at the user´s outlet will be lower
than 32 dB.
- The Channel Processors can be program-
med either in channel converter mode (dif-
ferent input and output channel) or in
channel amplifier mode (same input/output
channel).
If they are used as channel converters the
installer must make sure that the level of
the digital signal (or part of it) passing
through the part of the headend handling
the analogue channels is low enough as to
not make the Set Top Box to lock it. The
output channel frequency should be lower
than that at the channel converter input.
It is quite likely that the processors are
commonly used with the same input and
output channel to avoid tuning problems
with the set-top box.
When used as amplifiers (same input and
output channel) it is highly recommended
to use processors for the analogue chan-
nels as well. Processors for the analogue
channels must be the same as those for
digitals (ref. 5870 or 5871)
In any case, it will not be possible to use
channel processors as amplifiers for the
digital signals and broadband amplifiers for
the analogue channels (the STB would
"see" the digital cahnnels twice, the one
passing through the broadband amplifier
and the same channel passing through the
channel processor).
If it is not possible to use channel proces-
sors for the analogue channels, use at
least high selectivity channel amplifiers.
- If channel processors are used as ampl-
fiers, and the processed digital channel us
upper adjacent to an analogue one, an off-
set must be selected for the digital channel
according to the next table:
- For CCIR 8 MHz (UHF) TV channels,
standard B/G, set both input and output
offset to +1.
- For CCIR 8 MHz (UHF) TV channels,
standard I, set both input and output
offset to +3.
- For CCIR 7MHz (BIII and UHF) TV chan-
nels, Australia, set both input and output
offset to +3.