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Activating The Modern Return Plant
Presented By
Michael E. McCracken
Eastern Show ‘96
Presented By
Michael E. McCracken
Eastern Show ‘96
2 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantTopics
3 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReturn Path Overview
AM Fiber LinkCoaxial Distribution HeadendTransport
Drop
4 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantThe Forward & Return RF Spectrum
5MHz 750MHz
Return Forward
40MHz 54MHz
SystemSplit
2 3 4 5 6 …..
5 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantTwo-Way Amplifier
54-750MHz
5 - 40MHz 5 - 40MHz
54-750MHz
Forward Amplifier
ReturnAmplifier
Dip
lex
Filt
er
Dip
lex
Filt
er
C
H
L
H
C
L
From/ToHeadend
To/FromSubscriber
6 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantDiplex Filter Crossover
5MHz 750MHz
Return Forward
40MHz 54MHz
Crossover
Am
pli
tud
e
7 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantAM Fiber Link
Diplex Filter
Forward Receiver Forward Transmitter
Return ReceiverReturn Transmitter
Forward Fiber
Return Fiber
AM Optical Node
Hub or Headend
To/FromDistributionSystem
8 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantRF Impulse-Pay-Per-View
AM Fiber LinkCoaxial DistributionDrop
SettopTerminal
HeadendTransport
ControlSystem
9 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantRF-IPPV Frequency Allocation
5 MHz 40 MHz10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 35 MHz
vv
15.45MHz 17.75MHz
10 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantRF-IPPV Bandwidth Utilization
15.45 MHz 17.75 MHz
2.3MHz23 Channel Slots
100kHz
11 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantHigh-Speed Cable Modems
AM Fiber LinkCoaxial DistributionDrop
SettopTerminal
HeadendTransport
Interface
12 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantCable Modem Frequency Allocation
5 MHz 40 MHz10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 35 MHz
13 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantCable Modem Bandwidth Utilization
5 MHz 40 MHz10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 35 MHz
1 MHz
14 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantCable Telephony
TelephoneInterface
AM Fiber LinkCoaxial DistributionDrop HeadendTransport
Interface
15 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantCable Telephony Frequency Allocation
5 MHz 40 MHz10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 35 MHz
50 kHz
1 Voice Channel = 50kHz
16 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantCable Telephony Bandwidth Utilization
5 MHz 40 MHz10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 35 MHz
240 Channels in 12MHz
17 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantStatus Monitoring
MonitoringSystem
AM Fiber LinkCoaxial DistributionDrop HeadendTransport
18 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantStatus Monitoring Frequency Allocation
5 MHz 40 MHz10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 35 MHz
29.8MHz Typical
19 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantStatus Monitoring Bandwidth Utilization
5 MHz 40 MHz29.8MHz
250 kHz
20 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantInteractive Services
Video Server
AM Fiber LinkCoaxial DistributionDrop HeadendTransport
DigitalSettop Terminal
21 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantInteractive Services Frequency Allocation
• One or more channels
• Frequency Agile
5 MHz 40 MHz10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 35 MHz
Signaling Channel
22 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantInteractive Services Bandwidth Utilization
5 MHz 40 MHz10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 35 MHz
1.0 MHz
23 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantCurrent Bandwidth Utilization
5 MHz 40 MHz10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 35 MHz
RF-IPPV Telephony
Cable Modem Status Monitoring
Interactive Services
24 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantProposed Bandwidth Allocation
5 MHz 40 MHz10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 35 MHz
RF-IPPV Telephony
Cable ModemStatus Monitoring Interactive Services
25 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantBandwidth Limitations
5MHz 750MHz
Return Forward
40MHz 54MHz
26 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantSegmented Reverse
FiberCable
Coaxial Distribution
Diplex Filter
Reverse Fiber Tx
Fiber Rx
27 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantBlock Conversion
OpticalReceiver
OpticalTransmitter
BlockConverter
BlockConverterCombiner
54 MHz 750 MHz
Reverse Block5 - 40MHz
Reverse Block5 - 40MHz
Upstream Blocks5 - 40 MHz
40 - 75 MHz75 - 110 MHz
110 - 145 MHz
35 MHz 35 MHz
54075
28 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantHigh-End Return
735 MHz
Forward
50 MHz 1 GHz
Return
900 MHz
29 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantThermal Noise
Carrier-to-Noise Ratio
Noise Energy
RF Carrier
30 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantNoise Accumulation: Forward
1 2
4 5
3
31 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantNoise Accumulation: Return
1 2 3
4 5
32 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantManaging Thermal Noise
Return TransmittersReturn Combining Network
Noise
33 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantRF Ingress
HA
M
HA
M
HA
M
HA
M
HA
M
40 M
20 M
15 M
CB
Lan
dM
ob
ile
40MHz
Land MobileCivil Air Patrol Civil Air Patrol
5.0MHz
Sub-Split Return Spectrum
Potential Ingress Sources
34 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantNon-RF Ingress
Power line conductedemissions and noise
Household electricmotor noise
Industrial electricmotor noise
Electrical switches
Electrostatic discharge
35 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantIngress Causes
DropDrop
Reports of 70 to 90% caused by drops and house wiring.
10 to 30% caused by coaxial plant problems.
36 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantDrop Cable
Tra
nsfe
r Im
peda
nce
Frequency
0MHz 1GHz
0 m/m
100 m/m
Headend Quad
60/40 Quad
60% Braid
Worse
Better
50MHz
37 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantRF Egress
Potential for Harmful Interference
HA
M
HA
M
HA
M
HA
M
HA
M
40 M
20 M
15 M
CB
Lan
dM
ob
ile
40MHz
Land MobileCivil Air Patrol Civil Air Patrol
5.0MHz
Sub-Split Return Spectrum
38 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantRules on Interference
• Concerned with “harmful interference”
– Radio navigation
– Safety of life and protection of property
– Radiocommunication services
• System Operator must eliminate the problem “immediately”
– Measures include service or even system shutdown
39 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantSummary
• Bandwidth is limited and must be carefully managed
• Thermal Noise is a natural phenomenon and must be managed
• Ingress points must be located and eliminated on a continuous basis
• Egress must be tracked down and eliminated to prevent interference with radio communications
• Bandwidth is limited and must be carefully managed
• Thermal Noise is a natural phenomenon and must be managed
• Ingress points must be located and eliminated on a continuous basis
• Egress must be tracked down and eliminated to prevent interference with radio communications
40 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantBasic Network
Headend•End of line•Far from Headend•Large house•Two outlets
•First tap•Closer to headend•Short drop•Small house•Three outlets
41 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantHeadend
Pad
Modulator
Combiner
Same Amplitude
RF Carriers
To Distribution
42 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantForward AM Fiber Links
Forward Tx Forward Rx
From Headend To Distribution
Fiber
Signal Input Signal Output
43 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantForward Unity Transmission
-24 -24 -24
+24 +24 +24 +24
ConditionEstablished
ConditionRepeated
FromHeadend
Gain = Loss
Output Level
Input Level
1 2 3 4
+24-24
0
+24-24
0
44 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantBasic Forward Amplifier
EQEQ InterstageSection
-20dBTest
-20dBTest
InputTest Point
OutputTest Point
PADInputAmp
OutputAmp
45 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantAmplifier Spacing
-24
+24 +24
1 2
-19
+24 +24
1 2
Obstacle(Water)
Normal Spacing
Short Spacing
46 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantAmplifier Pad
InputTest Point
InputAmp
+24dB
Desired Input = 11dBmVInput = 16dBmV
5
Attenuation24dB - 19dB = 5dB
Amplifier Output11dBmV + 24dB = 35dBmV
-19dB
Amplifier Input16dBmV - 5dB = 11dBmV
47 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantAmplifier Pad Application
-24 -20
+24 +24
+24
+24FromHeadend
1 2 3 4-22
5
-12
-11Pad: 24 - 24 = 0Input: 35 - 24 = 11
•Forward Pad used to achieve same input level on all amplifiers•Forward Pad used to achieve same input level on all amplifiers
+24
11dBmV
35dBmV
Pad: 24 - 12 - 11 = 1Input: 35 - 12 - 11 - 1 = 11
Pad: 24 - 20 = 4Input: 35 - 20 - 4 = 11
Pad: 24 - 22 = 2Input: 35 - 22 - 2 = 11
48 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantForward Amplifier Equalizer
EQEQ InterstageSection
-20dBTest
-20dBTest
InputTest Point
OutputTest Point
PADInputAmp
OutputAmp
49 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantCable Attenuation vs. Frequency
5 20 80 320 1280
1 2 4 8 16
4 x Frequency = 2 x Attenuation4 x Frequency = 2 x Attenuation
Attenuation Factor
Frequency in MHz
50 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantCable Loss Ratio
50 800 50 800
Flat Test Signal
Cable = 24dB at 800MHz6dB
24dB
50
8000 25
0 25 24 6
MHz
MHz
x dB dB
.
.
and
51 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantEqualizer Attenuation Curve
50 100 200 400 800
Att
enu
atio
n
Frequency in MHz
Equalizer
Cable
Equalizer + Cable
52 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantEqualizer Function
6dB
50MHz 100MHz 200MHz 400MHz 800MHz
8.5dB
16.5dB
13dB
12dB
17dB
8dB
19dB
1dB
Eq
ual
ize
r A
tte
nu
atio
n
24dB
25dB
Cable Attenuation
25dB 25dB 25dB
53 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantEqualizer Function
50 800
25dB
50 800
6dB24dB 25dB
Equalizer24dB
800MHz
Equalizer Input Equalizer Output
Equalizer Reference Frequency
54 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantPad and Equalizer Practice
-24 -20
+24 +24
+24
+24FromHeadend
1 2 3 4-22
5
-12
-11
Pad: EQ : Input:
+24
11dBmV
35dBmV
Pad: EQ : Input:
Pad: EQ : Input:
Pad: EQ : Input:
Pad: EQ : Input:
Includes EQ Loss
55 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantTransition to Tapped Feeder
-24 -20
+24 +24FromHeadend
1 2 3 4-17
+24
11dBmV
35dBmV
+30
35 - 17 = 18dBmV
18 + 30 = 48dBmV
56 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantEqual Loss Signal Splitting
-4 -4 -4 -4 -4 -4
-2 -2 -2 -2 -2
48dBmV
-4 -4 -4 -4 -4 -4
Distribution System with equal loss taps
44dBmV 38dBmV 32dBmV 26dBmV 20dBmV 14dBmV
•Unacceptable amplitude differences•Inefficient signal distribution
57 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantEqual Loss Distribution
-2 -2 -2 -2 -2
48dBmV
-1 -1 -1 -1 -1 -1
Distribution System with selectable attenuation
16dBmV 16dBmV 16dBmV 16dBmV 16dBmV 16dBmV
•Equal amplitude at all subscriber connections•Equal attenuation to all subscriber connections•Feeder amplitude preserved for additional distribution
32 29 26 23 20 17
Attenuation: (5 x 1) + (5 x 2) + 17 = 32dB
Amplitude: 48dBmV - 32dB = 16dBmv
58 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantSummary
• All signals aligned to common amplitude at Headend
• The Forward Fiber Link provides “transparent” transport
• The Coaxial Trunk system provides “Unity Transmission”
• The Coaxial Feeder provides equal distribution of available signal
• All signals aligned to common amplitude at Headend
• The Forward Fiber Link provides “transparent” transport
• The Coaxial Trunk system provides “Unity Transmission”
• The Coaxial Feeder provides equal distribution of available signal
59 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantBasic Return Network
Headend•End of line•Far from Headend•Large house•Two outlets
•First tap•Closer to headend•Short drop•Small house•Three outlets
Sources
60 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantSignal Combining
Pad
Modulator
Combiner
Same Amplitude
RF Carriers
To Distribution
61 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReturn Path as a Combiner
SourceSource SourceSource SourceSource SourceSource
SourceSource SourceSource SourceSource SourceSource
CommonTest Point
Combiner
Settops
Objective: Achieve desired amplitude and quality at common test point.
Objective: Achieve desired amplitude and quality at common test point.
HFC Network
62 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantSignal Combining at the Home
TV 1
TV 2
-5.5dB
75’ @ 1.67 = -1.25dB35’ @ 1.67 = -.58dB
10’ @ 1.67 = -.17dB
+55dBmV
+55dBmV
1 2 3
49.3 48.948.3
+55dBmV
Cable Modem
63 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantTerminal Calibration
TV 1
TV 2
-5.5dB
75’ @ 1.67 = -1.25dB35’ @ 1.67 = -.58dB
10’ @ 1.67 = -.17dB
+54dBmV
+54.4dBmV
1 2 3
48.348.348.3
+55dBmV
Cable Modem
64 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantCombining in the Feeder Plant
-.5 -.5 -.5 -.5 -.5-1 -1 -1 -1 -1 -1
48dBmV 48dBmV 48dBmV 48dBmV 48dBmV 48dBmV
32 29 26 23 20 17
Attenuation: (5 x 1) + (5 x .5) + 17 = 24.5dBAttenuation: 32dB
Reverse Amplifier Input
1: 16.0dBmV 4: 20.5dBmV
2: 17.5dBmV 5: 22.0dBmV
3: 19.0dBmV 6: 23.5dBmV
Reverse Amplifier Input
1: 16.0dBmV 4: 20.5dBmV
2: 17.5dBmV 5: 22.0dBmV
3: 19.0dBmV 6: 23.5dBmV
1 2 3 4 5 6
1 2 3 4 5 6
65 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantTraditional Concept
-.5 -.5 -.5 -.5 -.5-1 -1 -1 -1 -1 -1
48dBmV 46.5dBmV 45dBmV 43.5dBmV 42dBmV 40.5dBmV
32 29 26 23 20 17
Attenuation: (5 x 1) + (5 x .5) + 17 = 24.5dBAttenuation: 32dB
Reverse Amplifier Input = 16dBmVReverse Amplifier Input = 16dBmV
1 2 3 4 5 6
654321 Terminal output adjusted to compensate for path conditions
66 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantUnity Loss in Return Path
-.5 -.5 -.5 -.5 -.5-1 -1 -1 -1 -1 -1
48dBmV
48dBmV
48dBmV
48dBmV
48dBmV
48dBmV
32 29 26 23 20 17
Reverse Amplifier Input
Uniform at 16.0dBmV
Reverse Amplifier Input
Uniform at 16.0dBmV
Maximum output level for best carrier/interference
ratio
Maximum output level for best carrier/interference
ratio
0 -1.5 -3 -4.5 -6 -7.5
1 2 3 4 5 6
Return Path Pad
Attenuation: 32dB Attenuation: (5 x 1) + (5 x .5) + 17 + 7.5 = 32dB
67 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantSplitters and DCs in the Return Path
-.5 -.5-8
-.5 -.5-1 -1 -1 -1 -1 -1
48dBmV
48dBmV
48dBmV
48dBmV
48dBmV
48dBmV
32 29 26 23 20 17
0 -1.5 -3 -4.5 -6 -7.5
1 2 3 4 5 6
-.5 -.5-1 -1
48dBmV
48dBmV
48dBmV
14 11 8
-5.5 -7 -8.5
7 8 9
-.5
-.5
Total Attenuation always = 32dB
Amplifier Input Always = 16dBmV
1 Values are arbitrary examples
Total Attenuation always = 32dB
Amplifier Input Always = 16dBmV
1 Values are arbitrary examples
68 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantBasic Reverse Amplifier
EQEQ InterstageSection
-20dBTest
-20dBTest
InputTest Point
OutputTest Point
PADInputAmp
OutputAmp
RvrsAmp
Dip
lexe
r
Dip
lexe
r
-20dBTest
-20dBTest
EQEQPAD
-20dBRev Inj
69 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReverse Pads and EQs
EQEQ InterstageSection
-20dBTest
-20dBTest
InputTest Point
OutputTest Point
PADInputAmp
OutputAmp
RvrsAmp
Dip
lexe
r
Dip
lexe
r
-20dBTest
-20dBTest
EQEQPAD
-20dBRev Inj
70 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReverse Pad Application
-5
-8
+10 +10ToHeadend
+10 +10-4
-2 +10
-5 -1
AB
Gain vs Attenuation
Path A = 10 - (4 + 1) = 5dB
Path B = 10 - (2 + 8) = 0dB
Gain vs Attenuation
Path A = 10 - (4 + 1) = 5dB
Path B = 10 - (2 + 8) = 0dB
Amplifier #3 Input
1 2 3 A
B
71 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReverse Pad Application (con’t)
-5
-8
+10 +10ToHeadend
+10 +10-4
-2 +10
-5 -1
A B
Attenuation vs Gain
Path A = 10 - (4 + 1 + 5) = 0dBmV
Path B = 10 - (2 + 8 + 0) = 0dBmV
Attenuation vs Gain
Path A = 10 - (4 + 1 + 5) = 0dBmV
Path B = 10 - (2 + 8 + 0) = 0dBmV
Amplifier #3 Input
0dB Pad
5dB Pad
1 2 3 A
B
72 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReverse Pad Exercise
EQEQPAD+10dB+10dB EQEQPAD+10dB+10dB
EQEQPAD+10dB+10dB
Reverse Amp A
Reverse Amp B Reverse Amp C
-4dB
-1dB
-8dB
-1dB
73 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReverse Unity Transmission
-6 -6 -6
+6 +6 +6 +6
ConditionEstablished
ConditionRepeated
ToHeadend
Gain = Loss
Output Level
Input Level
+6-60
+6-60
1 2 3 4
74 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReverse Equalizers
EQEQ InterstageSection
-20dBTest
-20dBTest
InputTest Point
OutputTest Point
PADInputAmp
OutputAmp
RvrsAmp
Dip
lexe
r
Dip
lexe
r
-20dBTest
-20dBTest
EQEQPAD
-20dBRev Inj
75 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantCable Attenuation vs. Frequency
5 20 80 320 1280
1 2 4 8 16
4 x Frequency = 2 x Attenuation4 x Frequency = 2 x Attenuation
Attenuation Factor
Frequency in MHz
76 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantCable Loss Ratio
50 800 50 800
Flat Test Signal
Cable = 24dB at 800MHz6dB
24dB
50
8000 25
0 25 24 6
MHz
MHz
x dB dB
.
.
and
77 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantEqualizer Attenuation Curve
5 10 15 20 40
Att
enu
atio
n
Frequency in MHz
Equalizer
Cable
Equalizer + Cable
78 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReverse Equalizer Function
2.1dB
5MHz 10MHz 20MHz 40MHz
3dB
4dB
4.3dB
2.7dB
4.9dB
1dB
Eq
ual
ize
r A
tte
nu
atio
n
6dB
Cable Attenuation
7dB 7dB 7dB
79 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantEqualizer Function
5 40
7dB
5 40
2dB6dB 7dB
Equalizer6.0dB40MHz
Equalizer Input Equalizer Output
Equalizer Reference Frequency
80 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReverse Pad and EQ Practice
-6 -5
+10 +10
+10
+10ToHeadend
-5
-8
-2
Pad: EQ : Atten:
+10
Pad: EQ : Atten:
Pad: EQ : Atten:
Pad: EQ : Atten:
Pad: EQ : Atten:
Includes EQ Loss
-1
81 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReverse AM Fiber Links
Reverse Rx Reverse Tx
To Headend From Distribution
Fiber
Signal Output Signal Input
82 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantSummary
• All paths must have equal attenuation
• Reverse signals must be maintained at the highest possible levels
• 40MHz signals experience only about one fourth the cable attenuation of 750MHz signals
• Passive devices attenuate forward and reverse signals approximately the same
• All paths must have equal attenuation
• Reverse signals must be maintained at the highest possible levels
• 40MHz signals experience only about one fourth the cable attenuation of 750MHz signals
• Passive devices attenuate forward and reverse signals approximately the same
83 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantEarly Return Path Application
2 T9
Video/Audio returned to headend on Return Path channel
Return Path Channel translated to Forward Path channel
Subscribers view local video on Forward Path channel
84 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantBasic Alignment Technique
SignalSource
Technician 1
Injects calibrated test signal
Selects Pads and EQs
Technician 2
Informs Tech 1 of results
85 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantImproved Alignment Technique
2
Return Path signal displayed on analyzer
Technician views analyzer display on TV and makes adjustments to Return Path
SpectrumAnalyzer
Baseband Video
Camera views analyzer display
Camera output modulated to Forward Path channel
SignalSource
86 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantSweeping vs Balancing
Balancing with two carriers
• Only two reference points visible
Broadband Sweeping
• Hundreds of reference points
87 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReverse Sweep Equipment
Headend UnitField Unit
88 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantTypical Sweep Display
5MHz 40MHz
5db/Div
Ref Lvl +20dBmV
89 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReturn Path Activation Steps
• Install sweep system headend unit
• Configure sweep equipment
• Install and Align Reverse Fiber Link
• Install and Align reverse amplifiers in sequence, from first to last
• Install sweep system headend unit
• Configure sweep equipment
• Install and Align Reverse Fiber Link
• Install and Align reverse amplifiers in sequence, from first to last
90 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantInstalling the 3ST Transmitter
Co
mb
inin
g N
etw
ork
ForwardLaser
ForwardLaser
Return PathReceiver
Return PathReceiver
Ret
urn
Sig
nal
Bre
ak-o
ut
Diplex FilterH / L
Fiber Out
Fiber In
out
in
Sweep Signal -10 to -12dB
Telemetry Signal -5dB
Input -10dBmV to +10dBmv
91 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantConfiguring the 3ST Transmitter
• Enable Reverse Sweep
• Select Reverse Telemetry Carrier Frequency
• Create a Reverse Sweep Plan
• Select a Reverse Sweep Plan
• Enable Reverse Sweep
• Select Reverse Telemetry Carrier Frequency
• Create a Reverse Sweep Plan
• Select a Reverse Sweep Plan
92 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantSweeping a Fiber Node
ForwardReceiver
ForwardReceiver
ReverseTransmitter
ReverseTransmitter
LH
Fiber In
Fiber Out
From System
in out
3SR
External RF In
Forward Test Point
Fiber node
93 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantReverse Fiber Receivers
Return PathReceiver
Return PathReceiver
Ret
urn
Sig
nal
Bre
ak-o
ut
Diplex FilterH / L
Fiber In
in
Return PathReceiver
Return PathReceiver
Fiber In
Return PathReceiver
Return PathReceiver
Fiber In
Return PathReceiver
Return PathReceiver
Fiber In
Ret
urn
Sig
nal
Co
mb
iner
-8dB-11dB-0.5
-0.5
-0.5
+24dBmV
+3.5dBmV
94 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantInboard Test Points
LH
Coaxial
Cable
in out
3SR
Forward Test Point
LH
Coaxial
Cable
Two-way Amplifier with Test Point Inboard of Diplex Filter
95 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantOutboard Test Points
LH
Coaxial
Cable
in out
3SR
Forward Test Point
NS-6LH
Coaxial
Cable
Two-way Amplifier with Test Point Outboard of Diplex Filter
• Wavetek Model 3ST Operating Guide Section 5.1.3
96 GTS Enterprises, Inc.Wednesday, September 18, 1996
Activating the Modern Return PlantSummary
• Understand your Return Path application
• Know the design specifications
• Install and configure the sweep system headend equipment
• Align the Reverse Fiber Links for uniform receiver output
• Align the coaxial plant to have least impact on transmitted signals
• Understand your Return Path application
• Know the design specifications
• Install and configure the sweep system headend equipment
• Align the Reverse Fiber Links for uniform receiver output
• Align the coaxial plant to have least impact on transmitted signals