TechniSat GigaSystem 17/8 K - Handbuch (Seite 32)

Built-in distributor cabinet:
For installation in stairways, particularly suited where distribution originates at the centre of
the building, you should use a distributor cabinet that can be installed in or on the wall. When
necessary, this cabinet also provides space for an additional intermediate amplifier or other
devices.
The door should be locked with a built-in padlock
5.2 Planning
For large-scale installations a calculation of “coverage” is necessary. This means you must
consider the following points unconditionally:
1. Level
2. Isolation
3. Voltage drops
4. Load of power supplies
Satellite range
> Set up a construction plan showing all cable lengths involved
> The switching matrices work essentially without any loss of signal strength; avoid
levels above limits in the trunk lines. In the satellite range 75dBμV are recommended.
> Write down the expected and the required levels at the inputs and outputs of the com-
ponents see also: Technical data list and table 1.
> Please note: Where large-scale satellite distribution is involved, even minor errors or
incorrect calculations can add up to major overall problems.
> Avoid overloading the socket, and also avoid having the signal fall below the mini-
mum required level for the socket, see Table 2. A minimum BER (Bit Error Rate) or
the required C/N ratio (carrier-noise ratio) must be ensured at every point in the
system.
> Input signal range on receiver (regulation range): 44dBμV...84dBμV.
> Set the gain as well as the use of cables in such a way that the transponder levels at
the upper limit of the bandwidth do not fall below the minimum required level, which
can be caused by a drop in the frequency response of the LNB’s as well as the fact
that equalisation in the cable loss does not quite achieve theoretical maximum levels.
In reality though, can unfortunately levels here be as much as 10 dB lower than in the
middle of the band.
> Calculate whether the isolation is adequate. Each additional component added in
series will reduce isolation by approx.4dB. Isolation should not be less than 20dB at
the participant’s end.
> Estimate the effect of the voltage drop (reduced voltage) to be expected in the various
components. The voltage must still be adequate for the LNB’s as well as for any
accessory components (horizontal >16,5V, vertical >11.5V).
> Check the power load of the individual power supplies. The power consumption
values can be found in the technical data list.
> Add in some reserve capacity when making your calculations; this improves liability
and longevity of your system.
> If you are also utilising the return path, the signals of the individual participants (with a
reserve of 5 dB) must be within the input range of the head end tuner (generally
40...75dBμV).
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GigaSystem_17_8_deu_engl_23112011_3.qxp 28.11.2011 09:34 Seite 32