PT 5780 DVB-T Modulator
ProTelevision Technologies
Introduction and Applications
Instruction Manual
Revision 3.11
2-7
2.7
Test Facilities
The DVB-T Modulator PT 5780 features a range of useful test signal for both off-line and on-line
testing.
Single carrier:
The single carrier test signal is an off-line test signal (i.e. it interrupts the modulators data
transmission). When the single carrier test signal is activated the normal DVB-T spectrum is
substitutes for a single continuous sine wave located at the centre frequency of the normal in-
service DVB-T spectrum. The RMS level of the sine equals the average RMS level in the full
bandwidth of the normal DVB-T spectrum. The signal is therefore excellent for adjusting
transmitter level and/or verifying frequency accuracy or phase noise performance for the
modulator output.
-1 Carrier test signal
For special tests any single one of the carriers in the DVB-T spectrum can be switched off. This
test signal is in principle an off-line test signal. However, as the FEC of the COFDM coding will
normally cope with the loss of a single carrier without difficulty the signal can be activated during
normal transmission with marginal influence to the performance (slight increase in BER may be
noticed).
-50 Carrier test signal
To allow analysis of in-band intermodulation in a transmitter system 50 consecutive carriers in
the DVB-T spectrum can be switched off. The location of the 50-carrier hole can freely be
selected but typically the hole is placed at the centre of the spectrum. It is recommended to use
this test signal only for off-line tests. However, in most cases the transmission service is
maintained despite the loss of 50 carriers thanks to the FEC of the COFDM coding.
TS Stuffing
This test signal facilitates testing of a transmission systems IF and/or RF parameters even when
no MPEG-2 input is available (MFN mode only). When the TS Stuffing signal is activated a
pseudo random bit sequence as described in section 9.16.1 of the DVB-T Measurement
Guidelines ETR 290 is transmitted.
Summary of Contents for PT 5780
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