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ACTIVE COMBINER
CABLING
The interconnections between the units have to be
made with high quality, low attenuation cables. Such
cables (CW-3931 ... 34) and cable sets are included in
our company's product range, too.
Connecting cables made by the system installer can
also be used, however they must be made of high
quality cable. For making special cables, we offer
cables and connectors in a large choice.
At cabling always use the shortest possible cables.
Especially the cables connecting the converter and
modulator outputs to the inputs of the passive com-
biners must be very short. For connecting the outputs
of the passive combiners with the inputs of the
ACTIVE COMBINER longer cables are permitted to
be used.
After the cabling has been finalized, it is advisable
to mark all cables at both ends. This can easily be
accomplished using the CW-1940 CABLE LABEL
SET. Here, the identification mark will be written on
the mat white side, then the self-adhesive label will
be stuck on the cable.
LEVEL ADJUSTMENT
After having installed and cabled the system, switch
on all units and perform the adjustment of the levels
of the system.
The output level is to be set according to the number
of the TV channels. Transmitting 80 TV channels and
48 radio channels, the nominal level of the high level
output can be 112 dBµV. Adjust the level of the digi-
tal channels with 64 QAM by 10-15 dB, and the
nominal output level of the radio channels by 10 dB
below the level of the analogue TV channels.
Measuring the nominal level of the digital chan-
nels with spectrum analyzer:
The actual level of the QAM signal is established by
adding a correction value to the spectrum analyzer
reading. For a digital signal of 8 MHz channel band-
width, at 100 kHz spectrum analyzer resolution
bandwidth (RB), the correction value is 21 dB, thus
the actual level of the signal is:
U
[dB] = Spectrum analyzer reading [dB] + 21 dB
QAM
For the example of Fig. 2:
U
= 99.78 + 21 = 120.78 dBµV
QAM
Correction values for the most frequent cases:
RB
30 kHz
100 kHz
300 kHz
1 MHz
3 MHz
Correction value
26 dB
21 dB
16 dB
11 dB
6 dB
Fig. 2. Measuring the signal level of the digital channel
with spectrum analyzer
The output levels can be adjusted with screwdriver
attenuators on the rear panel.
Recommended sequence of adjusting the output levels:
1. Analogue channels.
2. Digital channels.
3. FM radio channels.
4. Adjusting the level of the signal combined of the
above channels, using the OUTPUT LEVEL at-
tenuator.
ADDITIONAL INFORMATION
1. The main output (OUT) of the 'REVERSE PATH
OUTPUTS 5-65 MHz' module has to be termi-
nated with a 75 Ω F-type termination plug.
2. The main output (OUT) of the 'LOW LEVEL
OUTPUTS 47-862 MHz' module has to be termi-
nated with a 75 Ω F-type termination plug.
3. The main output of the 'HIGH LEVEL
OUTPUTS 85-862 MHz' module has to be termi-
nated with a 75 Ω F-type termination plug, when
measuring signal level at the CONTROL
OUTPUT.
4. The unused inputs of the ACTIVE COMBINER
should be terminated with 75 Ω F-type termina-
tion plugs, for having an amplitude response less
by several dBs.
GENERAL INFORMATION
The type number and serial number of the unit is
marked in a label on the unit's side cover.
The ACTIVE COMBINER needs no adjustment, it is
sufficient to check up the adjustments once in a year.
Dear Customer!
We hope, this guide will effectively support you in
your job. Should you have any question when using
the unit, our experts are at your disposal at any time.
3
CW-4076
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