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8/8/2019 Terrestrial Broadcasting 1
http://slidepdf.com/reader/full/terrestrial-broadcasting-1 1/28
Generation of C C V S
Review of the PAL Composite Video Signal
Starts with the RBG component signal.
Matrix creates color difference YUV signals.
Analog Composite
Video (PAL)
R
Y
V
U
COMPOSITE
ENCODER
B
G
Composite
Analog Video(RGB)
Color Difference
Composite
Analog Video (YUV)
M
A
T
R
I
X
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TIMING DETAILS OF C C V S
Sync and Burst Amplitude both should be 300mv.
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COLOUR TRANSMISSION
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SATELLITES
Presently to INSAT-2A (74oE) andINSAT-2B (93.5oE) and INSAT 2E (83o
E). Down link frequency bands beingused are C-Band (3.7-4.2 GHz) and Ex-C Band (4.5-4.8 Doordarshan is up
linking its national, and regionalservices
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TRANSMISSION OF BASE BAND
TO SATELLITE
The base band signal consists of video (5 MHz),two audio subcarriers (5.5 MHz & 5.75 MHz)
and energy dispersal signal (25 Hz). Aftermodulation (70 MHz) and upconversion (6 GHz)the carrier is amplified and uplinked throughSolid Parabolic Dish Antenna (PDA). Down linksignal can be received through same PDA using
Trans-Receive Filter (TRF) and Low NoiseAmplifier (LNA). After down conversion to 70MHz, it is demodulated to get audio and video.
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EARTH STATION UP
LINK/DOWN LINK
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SATELLITE TRANSPONDER
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Figure of Merit (G/Teq)
Down link Carrier to noise density of a
satellite down link signal is given as
( ) k loss Path
T
G EIRP
N
C
eq
sat
Do
−−+=
where k is boltzman's constant (-228.6 dB/degree
Kelvin
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Azimuth and
Elevation
Both the azimuth and elevation of a dish can
be affected by three factors for geo-stationarysatellites. They are The longitude of the
satellite. The latitude of the place. The
longitude of the place.
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LATITUDE AND LONGITUDE
LATITUDE ASANGULAR DISTANCEPARALLELSOF LATITUDE
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LONGITUDE
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CALCULATION OF ANGLE OF
ELEVATION
Where
R = Radius of the earth (6367 kms)
R = Radius of Synchronous orbit (42,165 kms)
Ø = Latitude of the earth station
D = difference in longitude of the earth
station and the satellite. (λ r - λ s)
( )
φ−
−φ= −
2
1
Cos.DCos1
R
r Cos.DCos
tanElevation
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CALCULATION OF AZIMUTH
where D = λ r - λ s in degrees.
Ø= latitude of the given site in degrees.
λ r = longitude of the given site indegrees.
λ s = longitude of the satellite.
( )( )φ sintantan180 1 Dazimuth o −
±=
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POLARIZATION
Circular or Elliptical
Right hand circular (RHCP) b)Left half circular (LHCP).
LINEAR POLARIZATION
Vertical (v) b) horizontal (h)
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SYNTHESIZED TVRO SYSTEM
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LOW NOISE BLOCK
CONVERTER
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TVRO BLOCK DIAGRAM
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PSU PSU PSU
AVR 50KVA Isolation
TFR 50
KVA
P s
1 - P
s 5
PA 1
PA 1
PA 1
PA 1
PA 1
PA 1
PA 1
PA 1
8
W
A
YS
P
L
I
T
TE
R
8
W
A
Y
CO
M
B
I
N
ER
AHU
Driver A
LCD
Touch
Screen
Driver B CPU
CPU
Multiplexer
input output
VA
V
A
EX-B
EX-AVrf O/P Diple
xer
CIBD
3 dB
Divider
PA 1
PA 1
3 dB
Divider
1600w6dBArf
13dBm
6dB
Driver A&B
CPU
To Txr
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Video + IF
Processor
EXITER
IF/RF
Converter
Interconnection Board
Sound + IF
Processor
IF/RF
Converter
Local
Osc.
Video I/P
1V PP
75Ω
IF O/P
38.9 MHz
-4 dbm VRF O/P
19 dbm
For Ch#5
175.25 MHz
To Control
System
600Ω
+6dbm
Audio2
Audio1
180.25 MHz
For Ch # 5-4dbm
IF O/P
33.4 MHz
ARF O/P
13 dbm
For Ch#5
214.25 MHz
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AURAL MODULATOR
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Representation of the side bands
in VSB transmission
Sound Carrier Picture Carrier
Parto
fL.S
.B
U.S.B
-1.25 –0.75 0 5 5.5
Frequency MHz
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RECEPTION OF VESTIGIAL SIDE
BAND SIGNALS
1600 O
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1600 W POWER AMPLIFIER
PhaseGain2 dbm
I/P T8MRF
182
Hybrid
MHL
8118
Pre-Amp
T7
Driver
AB
Driver
Driver
PCB
3
WA
Y
S
S
P
L
I
T
T
E
R
13 A20 W
13 A
20 W
13 A
20 W
T1
T2
T1
T2
T1
T2
10 W
10 W
W
IL
K
I
N
S
O
N
C
OM
B
I
N
E
R
3dBCombiner
Front panel
sample
600 W
600 W
600 W
1600 W O/P
3dB Divider
PA PCB AGC VSWR
Combiner PCBDC Biasing & Distribution Board
3.4 V biasingDrain 50 V
Over Drive
Protection
Over Current
Protection
VSWR
Protection
Safety Interface Board
Preamp board
CONSTANT IMPEDENCE BAND
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CONSTANT IMPEDENCE BAND
PASS DIPLEXER
OPF
STUB +2fs
- 2fs- fs
H2
BPF1
BPF2H1
A in
E
(4))
(3)
(2)(1)
R
A
B(3') (4')
(1'))
(2')
HF
Output
V in
CIBD
ea
(VP-P)
ev(VP-P)
ea
√2∠
0
o
ea
√2∠-90
o ∠-90oev
√2
ev
√2∠0
o
ev
ev & ea
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TRANSMITTING TOWER
UPPER BAY
1 to 12
2 to 24
L Meter
L + λ/4 Meter
Matchers for
Fine Tuning
Matchers for
Fine Tuning
12 Branch
Feeder Cables
LOWER BAY
1 to 12
2 to 24
L Meter
L + λ/4 Meter
Matchers for
Fine Tuning
Matchers for
Fine Tuning
12 Branch
Feeder Cables
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TV Demodulator (TVDM) is a precision monitoring
equipment for checking the quality of a TV
Transmitter in the VHF and UHF bands. It is similar to a precision TV receiver in many respects. The
function of the TVDM is to recover the picture and
sound signals from the carrier output.
TV DEMODULATORS
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TV DEMODULATOR BLOACK
DIAGRAM
PSU
+12V
-12V
-55V
230V
AC
Local Osc
Filter
RF IN
Mixer
IF IN
Inter Carrier Processing
SoundDiscriminator
LS
AF Out
DEV
VideoOutputNyquist Filter
AMP
AGC AMP
ENVDetector
SynchronousDet ector
Gating Pulse
Processor
VID AMP
Zero Ref Pulse
Processor
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SAMPLING AND QUANTIZATION