Promax 10 SE, Руководство пользователя

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USER’S MANUAL. PROMAX-10 Premium
Page 24 11/2008
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 Premium 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 Premium 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
Figure 18.- CSO and CTB
measurement.
When pressing the rotary selector
[9] again, we will access to the CSO-CTB
distortion products measuring screen.
First of all it will appear the message
REMOVE
CARRIER . PRESS TO MEASURE . 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 instrument has detected the absence or not of carrier.
At the lower part of the display it is shown 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 c V/A +C/N (paragraph 4.2.3.1.1).
Figure 19.- Measuring a digital
channel.
4.2.3.1.4 Power and C/N ratio measurement (DVB-C / DVB-T / DAB)
(only for digital channels)
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 with its related channel
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.