Promax 8 plus Manual Del Usuario Y Operador página 79

INSTRUCTION MANUEL. PROMAX-8+
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 PROMAX-8+ performs this measurement
automatically at four frequencies around the video carrier (-1.5, -0.5, +0.5 and +1.5
MHz). These frequencies can be modified by the user, see Channel-Frequency mode
configuration menu (section 4.2.3.3) .
Figure 17.- Interpretation of the CSO and CTB measures.
The PROMAX-8+ displays as CSO value the worst measurement (that is 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 +0.5 MHz).
May 2001 Page 23