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F
REQUENCY:
Parameter that characterizes the radio-
electrical wave. It is measured in “Hertz“. We usu-
ally use
some multiples of this unit: kilohertz (kHz), megahertz (MHz), gigahertz (GHz).
ex.: At Saint Etienne (Guizay), the TF1 frequency is 583.25 MHz
H
P/LP:
high/low priority
possibility to transmit 2 multiplexes under the same channel in digit format (
ex.: in COFDM, we have a very robust high priority flow in QPSK; secondary flow in 16QAM)
G
UARD INTERVAL:
The guard interval is the time when the signal is not emitted: all signals carrying
the same
information but coming from different sources (various emitters or through multiple reflections) won't dis-
turb
each other.
Value for DTT: 1/32 (28µs), that permits echoes lower than 8.4km
I
SOFREQUENCY:
(or SFN: Single Frequency Network)
A DVB-T emitter network that emits on a whole region or a country at the same frequency.
risk of echoes outside the guard interval
moving reception
L
NB:
Low Noise Block-converter
A LNB (or universal head) is a standard converter for the analogical and digital reception of a satellite.
The reception is made on 2 low/high frequency band and 2 horizontal/vertical polarizations of the received
wave.
The commutation of the band is made by a 13/18Volt voltage. The commutation of the polarization is
made by a 22kHz signal superimposed to this voltage (you can also use the DiSEqC commutation for
some LNB).
L
DPC:
Low Density Parity Checker
An algorithm used to correct errors in transmissions of digital satellite transmissions DVB-S2 signals.
N
OISE MARGIN:
Difference between the measured and the theoretical noise level before incorrigible
errors.
Difference in dB between the measured C/N and the minimum C/N for error-free transmission.
M
ER
:
Modulation Error Ratio
Ratio in dB measuring the distance between the theoretical dot and the observed dot on a constellation
quarter. You can use it to control the reception:
the higher this value, the better the image
.
Communication
control
LNA+MIXER
Local Oscillator
10,6 GHz
Local Oscillator
9,75 GHz
22kHz
0kHz
18V
13V
H
V
Waves
Exit
BIS
