Operating Instructions
ProTelevision Technologies
PT 5780 DVB-T Modulator
Instruction Manual
Revision 3.11
4-24
instrument in question. The menu allows furthermore the user to input a new options key if
additional options are to be installed/enabled at a later date.
The CONFIGURE – STATUS MENU ID (menu ID 5B00) configures the manner in which the
status menu ID shown in the bottom right hand corner of every Status Display window (See
Chapter 4.3.3) is displayed. It can either be turned off (“Off”), flash, or be displayed as normal.
4.3.4.8
TEST SIGNAL Menu System (Menu ID 6000)
The TEST SIGNAL menu system is only available if the CONFIGURE – LOCK – TEST menu
option (menu ID 5100) is “OFF”. In addition, the TEST SIGNAL status window is only available if
a test signal has been selected from the TEST SIGNAL – SELECT TEST menu option (menu ID
6100). The default test signal mode is “OFF”
Sub menus are available for selecting a specific test signal (Single Carrier, -1 carrier, -50 carrier
and TS Stuffing) and for setting parameters for a test signal where applicable (for example
specification of which carrier to be removed with the –1carrier test signal).
The test signal functions are only for MFN mode. Per definition SFN mode does not allow
transmission of signals that are not bit synchronous to the signal transmitted from the other
transmitter of the network.
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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