TELE-audiovision - The World’s Largest Digital TV Trade Magazine - page 46

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TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine
— 09-10/2013
90. Just like with the handheld
signal analyzer DS2400T intro-
duced in the 1209 issue of TELE-
audiovision, a long duration bit
error rate (BER) measurement is
also available. The time interval
can be selected and from that
point on a graphic shows the
progression of BER and MER.
This helps to identify intermit-
tent problems.
91. An additional measurement
for DVB-C signals is available,
namely the EVM or Error Vector
Magnitude. This measurement
resembles the MER measure-
ment but here a different refe-
rence is used: while the RMS
value of a QAM signal is used
for determining the MER, for
the EVM measurement the peak
value of the QAM signal is used
as a reference. The EVM measu-
rement presents the ratio of the
error vector amplitude versus an
ideal vector amplitude and helps
with the identification of interfe-
rence in signals under the QAM
mask.
92. The so-called Tilt measure-
ment shows the bars for each
channel in increasing frequency
from the left to the right so that
the line connecting the first bar
to the last bar shows the tilt. Ide-
ally, the line should be as hori-
zontal as possible. A large tilt in
the line suggests attenuation in
the upper frequency range (or
lower frequency range) and can,
for example, be compensated
for with the proper amplifier.
93. For the Barscan measure-
ment up to 16 channels can be
selected – you can choose only
analog, only digital or a com-
bination of analog and digital
channels.
94. Here only analog channels
were used for the Barscan mea-
surement.
95. Digital channels were now
measured (in blue) at the same
port. It’s obvious that the signal
is falling off for the four digital
channels on the right side. The
attenuation is too high.
96. The so-called Barscan mea-
surement is nearly self-explana-
tory and is where the level and
power of the selected channels
are displayed as a bar graph.
With analog channels the video
level is shown in green and the
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