Promax -10 Manual Del Usuario página 90

The CTB measurement is performed equivalently to the CSO . If all the channels
that are transmitted have the video carrier at the same position within the channel, then
the CTB beat will show up at the same frequency as the video carrier. It is for that
reason, that the PROMAX-10 makes this measurement at the same frequency as the
video carrier and, as consequence, to make this measurement it is necessary to turn
off the video carrier of the channel we want to analyse. If it is not possible to turn off the
carrier at the head-end, the PROMAX-10 allows, like approach, to make this
measurement at one of the free adjacent channels (see section 4.2.3.3. Channel-
Frequency mode configuration ).
MEASURING METHOD
When pressing the rotary selector
[9] again, we will accede to the CSO-CTB
distortion products measuring
First of all it will appear the message PRESS TO
MEASURE. REMOVE CARRIER . That is to say,
once the video carrier level on which it is desired to
make the measurement appears on the screen,
you must press the rotary selector [9] in order that
the unit retains the carrier level and comes to
calculate the CSO and CTB ratios; next you must turn off the video carrier of the
channel you want to make the measurement (at the right of the CTB measurement will
appear the message Carrier OFF ).
The display will show the level of the video carrier (80 dBµV in the previous
figure) and the CSO ratio (accompanied by the frequency offset for which the minimum
ratio has been obtained) and the CTB ratio (with the message Carrier OFF or Carrier
ON according to the equipment has detected the absence or not of carrier).
The lower part of the screen shows the 4 measures made for the estimation of
the CSO value.
If the rotary selector [9] is pressed again, the unit will return to the measurement
screen of the video carrier + V/A +C/N (paragraph 4.2.3.1.1).
4.2.3.1.4 Power and C/N ratio measurement of digital channels (DVB-
C / DVB-T / DAB).
When the tuned channel has been defined as
digital by means of the Edit Channel Plan function (see
section 4.2.1 Global Configuration Menu ) a screen as
shown in the attached figure will appear. This screen
shows the digital CHANNEL POWER (40 dBµV in the
example) together
bandwidth ( BW = 8.0 MHz) and the Carrier/Noise
ratio ( C/N =17 dB). At the bottom of the screen, as
in the case of analogue channels, a bar-graph
represents the channel power, with a resolution of 1 dB.
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screen.
with its related channel
USER'S MANUAL. PROMAX-10
Figure 16.- CSO and CTB
measurement.
Figure 17.- Measuring a digital
channel.
04/2004