General Requirements; Determining System Levels - R&S N 8000 Series System Manual

4.3.1

General 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.

Precorrection must be on, for which the Nonlinear control panel must be selected in the
precorrector graphical interface. A precorrection curve consisting of a straight line posi-
tioned on the X axis must be set for the amplitude precorrection and another for the
phase precorrection.
4.3.2

Determining System Levels

The graphical area contains lines representing distinctive signal levels such as all-white lev-
el (Wht), all-black level (Blk) and sync pulse level (Sync), as well as sync pulse level (Sync/
Aud) in the case of ATV combined. In DVT the level lines indicate the peak level (Peak) and
the average value (Avh). These marks indicate maximum level; the actual level may be dif-
ferent.
Changes to the set curve that affect only the range above the system level have no effect
on the signal or on precorrection of the signal.
The following method can be used to determine the actual values:
1. Use two interpolation points to determine the ends of the effective dynamic range in or-
der to define the possible setting range of the precorrector:
a) Add two interpolation points to the amplitude precorrection graph in the area above
the highest mark and set their slope.
You now have four points, consecutively numbered 1 to 4 from left to right. Points 2
and 3 are each indicated by an arrow.
b) Shift points 3 and 4 in the positive Y direction by +50%. Point 3 should then be im-
mediately adjacent to point 2.
c) Use the Write button to write this curve to the precorrector.
2. Now use the Navigator window to reduce the position of interpolation points 2 and 3 to-
gether in steps of one percent. Observe the effect:
ATV Split
ATV Combined
DTV
The upper of the two interpolation points thus represents the determined dynamic range limit.
3. Restore the original status.
2098.0188.72
Chapter 4
In ATV split systems, the first effect is seen in the sync pulse length, which
can be clearly observed on the TV demodulator (sync pulse length dis-
play) or the TV analyzer.
In ATV combined systems, the first effect is seen in the intermodulation
products about the two sound carriers f
In DTV systems the effect is seen as a reduced shoulder distance
- 4.33 -
Commissioning
± default f(T2-T1)
Tx
E-1