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signals (up to 8 signals) is shown on the screen. The echo signals are arranged in the
descending order of amplitude.
To change the measurement parameters, press the F1 / Settings key. The following
settings will be listed in the dropdown menu:
1) Zone. Selecting the echo signal delay range indicated on the diagram: Full-echo
– the full delay range supported by the Analyzer, Pre-echo – the negative delay
range, Post-echo – the positive delay range, Near-echo – the range close to the
main signal;
2) Resolution. The delay resolution of echo diagram measurement: Normal – fast
echo diagram measurement with rough delay estimation, High – slow echo
diagram measurement with precise delay estimation;
3) Units. The delay measurement unit: Distance – additional distance traveled by
echo signal in reference to main signal in km or miles (depending on regional
settings), Delay – echo signal arrival time in reference to main signal.
4.3.7. Equalizer parameters measurement of DVB-C and J.38-B/C channels
This mode allows displaying the parameters of signal demodulator equalizer, as well
as the common quality parameters of DVB-C and J.83-B/C channels reception. The
screen view and the data displayed are presented in Fig. 4.15:
The equalizer is intended for correcting the amplitude and phase response of the
received signal, thus enabling higher quality of reception in presence of distortion. That is
why the equalizer parameters analysis allows estimating the signal correction level in
terms of quality and quantity, and thus determining its distortion.
The equalizer parameters are presented graphically. The following display modes are
available for selection from the drop down menu by pressing the F2 / View key:
1) Equalizer taps. This mode allows viewing the gain values diagram for each of the
equalizer taps. The values are shown in dB in reference to the central tap having
the gain value of 0 dB. Each equalizer tap enables the signal delay equal to time,
which is a multiple of symbol duration. When receiving the ideal signal, all of the
equalizer taps energy is concentrated in three to five taps to the left and to the
right of the central tap. In case of distortion, the energy is distributed to the larger
number of taps. A peak value at one or several taps is the evidence of the
reflected signal arrival. Gain value and tap signal delay in the cursor position are
indicated in the bottom part of the screen. If you select the Distance
measurement unit from the F1 / Settings dropdown menu, the screen view will
display the distance
the signal was reflected instead of delay. Each of the tap bars has a marker of
1
For distance calculation, relative signal propagation rate in cable is assumed to be equal to 0.87
Figure 4.15
1
from the signal source to obstacle at the boundary of which
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