Specifications

3-58 888-2857-001 5/9/13
WARNING: Disconnect primary power prior to servicing.
Section 3 Operation
Platinum VAX-C Series
Guard Interval Choices are 1/4, 1/8, 1/16, and 1/32. The Guard Interval is the time, between
symbol transmissions, when nothing is transmitted. The guard interval is
entered as a fraction, which represents the guard interval time as a fraction of
the useful symbol duration. Total symbol duration is the sum of the useful
symbol duration plus the guard interval. In the 2k mode, useful symbol
duration is 224 microseconds and in the 8k mode, useful symbol duration is
896 microseconds.
Constellation Choices are QPSK (Quadrature Phase Shift Keying), 16 QAM (Quadrature
Amplitude Modulation), and 64 QAM. Constellation refers to the size of each
RF sub-carrier constellation. When using the hierarchical mode, 16 QAM or
64 QAM must be selected.
Transmission
Config(uration)
Choices are Non Hierarchical or Hierarchical. Non Hierarchical modulation
allows transmission of only one data stream, the HP (High Priority) input.
Hierarchical modulation allows transmission of two data streams, the LP (Low
Priority) and the HP (High Priority) transport stream inputs. The Low Priority
stream has a higher data rate which produces a higher quality reproduction,
but it is less robust and therefore covers a limited distance. The High Priority
stream has a lower data rate which produces a lower quality reproduction, but
it is more robust and therefore covers a greater distance.
High Priority Code
Rate
Choices are 1/2, 2/3, 3/4, 5/6, and 7/8. These choices affect the convolutional
encoder code rate for the High Priority channel. It offers a choice between the
useful data rate (picture and sound quality) verses signal robustness (distance
the signal can be received). A code rate of 1/2 includes one forward error
correction bit and one data bit. This yields a lower quality signal which can be
received at a greater distance. A code rate of 7/8 includes one forward error
correction bit for every seven data bits. This yields a higher quality signal
which can be received at a much shorter distance.
Low Priority Code
Rate
Low Priority Code Rate: Choices are: 1/2, 2/3, 3/4, 5/6, 7/8. The Low Priority
Code Rate is only visible when in Hierarchical mode. These choices affect the
convolutional encoder code rate for the low priority channel.
Softkeys
Setup Displays Setup screen.
Exciter Home Displays Exciter Home screen.
Table 3-32 Xmtr Home>Exciter Home>Setup>DVB-T Modulator>Next x4
(screen 5)
Fields Explanation