USER’S MANUAL. TV EXPLORER II/II+
Page 42
12/2013
5.13.2
DVB-T/H (COFDM) Digital Channel Configuration
Press the
Measurements Configuration
[17] key to access to the
CONFIGURATION
menu and turn the rotary selector [1] to access the
COFDM
signals
parameters which can be defined by user and are described below:
1)
Channel BW
(channel bandwidth)
Enables the channel bandwidth to be selected between 6 MHz, 7 MHz and 8 MHz.
The selection of this parameter is essential for the correct operation of the tuner,
as it affects the frequency separation of the carriers.
2)
Guard Interval
The
Guard Interval
parameter corresponds to the dead time between symbols, its
purpose is to permit a correct detection in multi-path situations. This parameter is
defined according to the symbol length:
1/4
,
1/8
,
1/16
,
1/32
. To modify its value, by
turning the rotary selector [1], place the marker over the
Guard Interval
field and
then press it : a menu with the available values will appear. Turning the rotary
selector [1] select the desired value and finally press it to validate.
3)
Carriers
(Number of carriers)
It defines the number of modulation carriers between
2k
,
4k
and
8k
. To modify its
value, place the marker over the
Carriers
field by turning the rotary selector and
then press it: a menu will appear on the screen. Turning the rotary selector [1]
select the desired value for the Carriers parameter and finally press it again to
validate.
4)
Spectral Inv.
(spectral inversion)
This option enables spectral inversion to be applied to the input signal, though in
the majority of cases it should be in the OFF position (not inversion).
This configuration menu shows, besides the user definable
COFDM
signal
parameters, the value of the rest of signal parameters detected automatically:
Code Rate
Also known as Viterbi ratio, defines the ratio between the data bits
number and the total number of bits transmitted (the difference
corresponds to the number of control bits for the error detection and
recovery).
Modulations
Carriers modulation. It also defines the system noise immunity.
(QPSK, 16-QAM and 64-QAM).
Hierarchy
The
DVB-T/H
norm contemplates the possibility to make a
TDT
transmission with hierarchical levels, it is to say a simultaneous
transmission of the same program with different image qualities and
noise protection levels, in order the receiver can exchange to a
signal of smaller quality when the reception conditions are not
optimal.
