Kathrein 9986492 User Manual

 

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For the terrestrial digital transmission of television signals (DVB-T), the modulation 
type COFDM (Orthogonal Frequency Division Multiplex)  is used.   

In 2k mode, 1705 carries and in 8k mode 6817 carriers either QPSK-, QAM16- or 
QAM64 are modulated. 

DVB-T signals are transmitted in the so-called hierarchy modulation. Two MPEG 
transport streams of difference priority are simultaneously transmitted.  

The demodulated QPSK signals are decoded in the MPEG decoder and their con-
stellations are represented on the screen of the MSK 33.  

THE MSK33 can automatically represent the constellations of all possible modula-
tion types and  display the respective values.  

 

By pressing this softkey, 
you receive all data of the 
DVB-T signal (see left).  

 

Since it deals with the transmission of binary 
data for DVB-T, the bit error rate can be 
observed as measurement for the occurring 
transmission error in the data stream. The BER 
measurement is carried out before and behind 
the viterbi decoder and displayed on the 
screen. The bit error rate is the ration of the 
number of the received defective bits divided by 
the entire number of receive bits. The low bit 
error rate, which the MSK 33 can measure, is 

1.0 e-8. If  the measured value is below this value, the display of BER skipped to 
zero „0“ (no bit error available). The highest displayed BER is 1 e-2. Generally, it 
can be assumed, that the picture disturbance can occur for a BER of ca. ca. 2.2 e-
2 before viterbi. 

The conception of the MSK 33 allows the S/N ratio of the I- and Q- data stream to 
be displayed in addition to the C/N measurement on the digital carriers in the 
Const-menu.  The measurement is carried out after the QPSK demodulation and 
can be called in as an indicator for the noise on the I/Q signals.  Differences in the 
result to the C/N measurement in the spectrum menu can be caused by the com-
plex interfering influences of the digital signal or by differences in the input level. 
The SNR value is displayed on the upper edge of the TFT screen.  

The best value, which the MSK 33 can measure, is 32 dB.  

The carrier offset display represents the difference between set receiving fre-
quency on the MSK 33 and the transmission frequency of the digital signal in MHZ. 
With the cursor buttons,  ◄►,  you can switch to the next channel.   

Displays how many carries of the DVB-T signal are modulated. It is modulated  be-
tween the 2k mode (1705 carriers) and the 8k mode (6817 carriers). 

Displays the modulation type, with which the DVB-T carriers are modulated. The 
modulation types QPSK, QAM16 and QAM64 are possible.