Televes TDT+ User Manual page 14

User manual
d.- Modulation format
By pressing the buttons, the following
menu appears. This is the modulation
format.
Modulation 64QAM Modulation 256QAM
To modify the modulation format, the user
must press the and buttons, until the
desired value appears (16, 32, 64, 128, 256).
This menu does not appear if the SCAN
function is activated in the extended
menu (SCAN = ON).
In the automatic modulation format, the
transport stream modulation is a function of
the Viterbi rate of the input signal, with
64QAM being for Viterbi 1/2, 2/3, 3/4 and
128QAM being for Viterbi 5/6 and 7/8.
If the user wants to select a modulation
format that gives a greater QAM symbol rate
than 7.2 Mbaud, the modulation format menu
will flash on and off, thus indicating that the
selected format is incorrect and that a greater
one should be chosen. For example:
Input symbol rate: 27.5 Mbaud
Viterbi code at input: 3/4
Select. modulation format: 32QAM
Symbol rate in 32QAM =
(27.5 x 2 x 3 / 4 ) / 5 = 8.25 Mbaud
This symbol rate is greater than the
maximum of 7.2 Mbaud, therefore the user
must choose a greater modulation format,
64QAM or 128QAM. If, for example, 64QAM
is chosen, the symbol rate for the previous
values will be 6.875 Mbaud, and for
128QAM, 5.893 Mbaud.
e.- Output level control
By pressing the button, the following
menu appears. This is the output level
control, with a range from 0 to 99. To
modify the output level, use the
buttons. For example, 85:
14
f.- CBER
By pressing the
menu appears. This is the CBER reading, or
the error rate. Since this is a read-only
menu, neither the
buttons are in use. The first three digits
correspond to the mantis and the third
corresponds to the exponent. For example:
This indicates an error rate of 2.5 x 10
Once here, the main parameters of the
TDT+ module have been configured.
and
TDT +
button, the following
button, nor the and
-4 .