Seite 38 - TELE-satellite-1203

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TELE-satellite International — The World‘s Largest Digital TV Trade Magazine
— 02-03/2012
parameters for analog and
for digital channel. In this
way, you edit channel by
channel and save them in
the meter’s memory. Such
a list of the channels that
are present in a given ca-
ble network is called a band
plan of this network. Once
you have created a cor-
rect band plan for the ca-
ble systems you are about
to install and measure, you
can enter the Auto Meas-
ure menu item and make
the meter measure every
channel form the list one
by one.
However, it is also pos-
sible to scan an unknown
network. In such case, the
Digipro C-Max does a smart
thing: it recognizes fully
automatically all analog
channels as well as the QAM
modes and symbolrates for
the digital DVB-C channels.
For analog TV channels it
shows the video and audio
frequencies along with their
signal levels and S/N ratio.
The measurement results
screen for a DVB-C signal
is naturally more complex.
You get not only signal fre-
quency, QAM order, sym-
bol rate, channel power,
modulation error ratio
(MER) and carrier-to-noise
(C/N) readings but also a
graphic representation of
the constellation diagram.
By pressing a button you
can enlarge the diagram.
This is perfect to asses the
signal quality visually: the
tighter the green dots’ con-
centration in the center of
the squares, the less noisy
the signal is. Of course,
visual assessment is rather
subjective and not very ac-
curate, therefore there are
MER and C/N readings that
correspond to the quality of
the digital signal.
Furthermore, the Digipro
C-Max offers a spectrum
view. It produces a clean
picture of the frequency
spectrum with adjustable
span and amplitude. You
can set the following fre-
quency spans: FULL, 500,
200, 100, 50, 32, 16, and 8
MHz. Maximum amplitude
can be set from 60 to 120
dBµV in 10 dBµV steps. Di-
gipro C-Max creates a very
readable spectrum picture.
It does not take long to
scan the whole bandwidth.
Even the best looking
meter, and Digipro C-Max
looks great indeed, would
not be worth its price if its
measurement results were
improbable. Therefore, we
compared the results pro-
duced by the Digipro C-Max
with another high class ref-
erence meter. We are de-
lighted to announce that
the results were in perfect
agreement. Please exam-
ine Table 1 and Table 2.
Both for digital and analog
TV signals, the channel
power results were prac-
tically identical. Also the
MER measurements were
matching one another very
well indeed. The only differ-
ences we noted in the S/N
measurements, this, how-
ever, is common between
different meter brands.
That’s because S/N meas-
urements depend on the
particular frequency a me-
ter takes as a noise refer-
ence level. As a result, S/N
and C/N can be compared
only if measured with the
same meter model but not
when measured with dif-
ferent models and makes.
MER is a much better sig-
nal quality indicator as this
value can be measured with
different meters and you
can expect similar results
with any product. Our gen-
eral conclusion: Digipro C-
Max is a very accurate me-
ter and you can fully rely on
its signal strength and MER
A great highlight is an-
other positive feature: the
Digipro C-Max not only
takes measurements but it
can also play back digital
channel video and audio.
Once it locks to the signal,
it searches the NIT table
inside the transport stream
and based on the informa-
tions found there, the me-
ter displays a list of TV and
radio channels. The last re-
maining step is to select the
channel you want to watch
and press a button. Of
course, this works only for
FTA channels as the meter
does not have any CI slot
or smart card reader and
can not descramble PayTV
channels. The Digipro C-
Max does not display analog
TV channels either but tak-
ing into account how fast
the technology advances,
analog channels will disap-
pear from CATV networks
anyway quite soon. So this
is not something to care
Finally we come to a truel-
TELE-satellite expert Jacek
Pawlowski wears the installer's
vest from Satcatcher. The vest
offers multiple pockets for the
installer - and even matches the
Digipro C-Max protective case'
Table 1. Digital TV signal measurement results
Power [dBµV]
MER [dB]
C-Max Ref
C-Max Ref
256QAM 474 MHz
87,1 87,7 38,8 36,7
64QAM 474 MHz
87,1 87,7 37,9 36,8
256QAM 674 MHz
82,5 83 39,4 35,6
64QAM 674 MHz
82,6 82,8 38,7 35,4
Table 2. Analog TV signal measurement results
Power [dBµV]
S/N [dB]
C-Max Ref
C-Max Ref
Video 471,25 MHz
61,3 64,4 23,7 48,6
Audio 477,75 MHz
50,4 52
Video 576,25 MHz
64 63,7 26,1 17,7
Audio 581,75 MHz
50,3 49,8