User's Manual Part 1

Chapter 4 Commissioning
2098.0188.72 - 4.34 - E-1
Fig. 1 Determining system levels
4.3.3 Precorrection Procedure
4.3.3.1 Starting Precorrection
Requirements
The following requirements should be fulfilled prior to precorrection:
 The transmitter must be operated at its nominal power output and the system level must
be adjusted at all points.
 A spectrum analyzer must be connected to the transmitter output.
Note A measurement should be taken upstream of the output filter as the shoulders are difficult
to detect owing to the band limiting of the filter. When measuring signals using the spectrum
analyzer, it is important to ensure that the precorrection target (e.g. 38 dB shoulder dis-
tance) is well above the noise limit, but the frequency range of the spectrum analyzer is
such that no intermodulation is generated in its input section.
 Precorrection must be activated. In the graphics area for the amplitude and phase pre-
correction, two interpolation points are present in each graph: the first point is modula-
tion 0% with magnitude 0% or 0°, and the second point is modulation 100% with
magnitude 0% or 0°.
A DTV spectrum with clear shoulders should be visible on the analyzer.