Chapter 6 - TV Measuring Range
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10713 Vxx.11
In the case of a US-DOCSIS signal, the automatically detected de-interleaver depths are also
shown in the display. The variable de-interleaver is part of the J83B specification (in the case of
DVB-C and EURO-DOCSIS, the de-interleaver is fixed with I = 12 / J = 17).
Figure 6-9 DOCSIS ranging display
Scan
6.2.2.2.2
With this function, you can scan the entire TV range for DOCSIS signals.
For this, you must switch the instrument to channel input mode.
The scan function includes the automatic scan of the DOCSIS variants as described above. That
means that the instrument scans every channel with EUDOC64, EUDOC256, USDOC64 and
USDOC256.
The arrow keys have a dual function. After entry of a new channel, the menu item
2.FUNCTION
is
inverted. That means that the Program list decoder can be operated with the arrow keys. To start
the scan, first press the F5 key in order to activate the first function of the arrow keys. The scan is
then started by first tuning the measuring receiver to a channel at which the scan should begin.
Press the
↑
key to start the scan in the positive direction. Press the
↓
key to do the same in the
negative direction. When the band limit is reached, the scan continues at the other end of the
range. You can end the scan at any time by pressing
ENTER
. “SCAN” is shown on the display
while the scan takes place.
BER measurement (Bit Error Rate)
6.2.2.2.3
The measurement of the bit error rate aids in the determination of the quality of a DVB signal. To
determine the bit error rate, the error correction mechanisms in the digital receiver are used. The
data stream is compared before and after correction and the number of corrected bits is determined
from that.
This number is placed in a ratio to the total throughput of bits and the BER is calculated based on
that. With Euro-DOCSIS, there is only one error protection mechanism (Reed-Solomon). That
means that there is only one bit error rate (BER) here.
With US-DOCSIS, in contrast, there is an internal error protection (Viterbi) and an external error
protection (Reed-Solomon) as same as in DVB-S and DVB-T. For technical reasons, the
measuring instrument can measure only the bit error rate according to Viterbi (VBER) with US-
DOCSIS.
