UNAOHM
EP2500 (Rev. 0)
45
10 MPEG CARD
The MPEG module makes it possible to view non encrypted (free to air) digital transmissions. This,
however, is not the most useful function it performs in the instrument in which it has been fitted,
since the quality of a digital signal should not be judged by the TV-picture, but only by means of
specific measurements such as BER or the C/N ratio (although much less reliable and accurate).
The real value of this module lies in the identification of channel contents. Digital channels appear
as noise bands of variable width: a few MHz for SCPC transmissions, around 7 MHz for terrestrial
cable or aerial transmissions, approximately from 18 to 30 MHz for MCPC transmissions.
Specialized magazines supply all the information concerning satellite transmissions, but when
dealing with frequency conversion installations an exchange between channels is always possible.
The same problems may be caused by QPSK to QAM transmodulation
2
.
The MPEG module receives the DTS (Data Transport Stream) coming from the QPSK, QAM or
OFDM demodulator and supplies the name of the transponder, the Network data, the television or
audio programs which are separately available, the list of audio channels associated with each video
program; if the program is not scrambled, it is decoded and may be viewed.
10.1 HOW TO USE THE MPEG CARD
1. Tune to a digital channel.
2. The instrument should be set to one of the following modes: Spectrum, Span, Measure or TV.
Press the key DIGITAL (35) on the front of the instrument. This enables the suitable digital
module to be selected automatically depending on the selected band.
3. Set the parameters necessary to lock the signal. For correct use of the digital cards see the related
section of the manual. Figure 22 shows a QPSK display.
4. Press the key MPEG. Figure 23 will appear on the display.
⇒ NOTE: Since data are transmitted cyclically, not continuously, information may be downloaded
with a certain delay, which is normally kept within 30 seconds.
Figure 22 BER display of a QPSK signal
2
A transmodulation demodulates and decodes the channels of a digital satellite transponder, which normally occupies a
30 MHz bandwidth, into a digital terrestrial transponder containing the very same channels in a 7 MHz bandwidth.
NETWORK INFORMATION TABLE
NETWORK NAME: MEDIASET
O/P 19.0E LH
BACK
001 I1 VID 3200 AUD 01
002 C5 VID 3201 AUD 01
003 R4 VID 3202 AUD 01
004 TEST VID 3203 AUD 03
005 RDMT AUD 01
005 PROGRAMMES ON THE NETWORK
UP/DOWN = (Shaft Enoder) SELECT = (DIGI)
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