Promax 8 SE Manual De Instrucciones página 76

The distortion products of greater level and which usually fall within the channel
bandwidth are those of second and third order beats.
The CSO distortion (Composite Second Order) is defined, as a ratio of the peak
level of the video carrier to the peak of the distortion products of second order beat,
produced by the rest of channels. The ratio is expressed in dB and can be resembled to
a C/N measurement as it is desired to be maximum.
Similarly, the CTB, Composite Triple Beat, is defined as a ratio of the peak level
of the video carrier to the peak of distortion products of third order beat, which show up
at the same frequency as the video carrier.
In order to obtain these measurements, the carriers of the channel plan that is
desired to transmit, must be present in the network and the measurements must be
carried out for each one of the channels of the system.
Second order beats show up within the channel, around the video carrier, but as
the relative position of the video carrier in all the channels can be different, it is difficult
to determine where they are going to appear, as a consequence we would have to be
made a sweep within all the channel. The
measurement automatically at four frequencies around the video carrier (-1.5, -0.75,
+0.75 and +1.5 MHz). These frequencies can be modified by the user.
Figure 16.- Interpretation of the CSO and CTB measures.
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The
to say, the CSO ratio that has minor value) accompanied of the frequency offset for
which it has been obtained (for example, in the figure previous at +0.75 MHz).
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
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reason, that the
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
this measurement at one of the free adjacent channels.
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-1.5 MHz -0.75 MHz 0.75 MHz 1.5 MHz
SE displays as CSO value the worst measurement (that is
SE makes this measurement at the same frequency as
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USER'S MANUAL.
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SE
SE allows, like approach, to make
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SE
performs this
09/2013