TechniSat GigaSystem 17/8 K - Handbuch (Seite 34)

5.4 Calibration
Checking the satellite range
> Check the output signals provided by the LNB´s; they must be linear over the entire
frequency (< 5 dB fall-off). Any differences caused by the power flux density of the
satellite can be at least partly compensated by using different sizes of satellite dish
antennas, and/or using pre-amplifiers.
> A short circuit in the LNB connections or trunk lines will be indicated by the both
LED’s of the 17/8G (visible through the ventilation slits), please refer to chapter 7.
> Make a note of the levels and quality.
BER (Bit error rate) for digital signals, or
S/N (Signal / Noise ratio) for analogue signals
of selected transponders at the upper end of the bands.
> If possible, when you have completed adjusting the levels for the installation, make
printouts of the levels measured at the individual participant sockets. This will greatly
facilitate any search for problems that may become necessary at a later stage.
Checking the terrestrial signals
> If strong and weak signals are received from different directions, try to make the
reception of the strong signals weaker by adjusting the position of the antenna.
> If all the signals are received from the same direction, you can use either one or more
good trap circuits to equalise the signal strengths (e.g. TSF 2169/2, Art. No
0000/6042) or you use channel filters.
With knowledge of the band allocations, set the trap circuits using a professional
antenna calibration tool in such a way that the weaker signals are immersed in the
noise to a slightly greater extent.
> Where an FM signal is being fed into the terrestrial combiner, it may be necessary to
use an adjustable damping joint.
> If a very linear frequency response distribution of terrestrial means is needed, termi-
nate unused outputs of the participants with a 75?-termination.
To avoid interference from the satellite reception range, it may be advisable to switch off the
satellite receiver while receiving weak terrestrial signals.
Checking on the return path
Feed the test channel of the modem into the system at the point of the participant located
furthest from the distribution installation, and measure the signal arriving at the headend.
You must also consider the different losses caused by the switching matrices and by any
accessory components.
5.5 Options for combinations with other TechniSat multi-switch
systems
TechniSwitch 5/8 switching matrices may be used only in sub-distributions (see
Point 6.2) and then only where the maximum current feeding the receiver (generally 400mA)
will not be exceeded. Benefit: Energy savings.
Please note that in this case the terrestrial signal is not continuously available.
34
GB
GigaSystem_17_8_deu_engl_23112011_3.qxp 28.11.2011 09:34 Seite 34