Activating The Modern ReturnPlant
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 Plant
Topics
3
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Return Path Overview
AM Fiber Link
Coaxial Distribution
Headend
Transport
Drop
4
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
The Forward & Return RF Spectrum
5MHz
750MHz
Return
Forward
40MHz
54MHz
System
Split
2 3 4 5 6 …..
5
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Two-Way Amplifier
54-750MHz
5 - 40MHz
5 - 40MHz
54-750MHz
Forward
Amplifier
Return
Amplifier
Diplex Filter
Diplex Filter
C
H
L
H
C
L
From/To
Headend
To/From
Subscriber
6
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Diplex Filter Crossover
5MHz
750MHz
Return
Forward
40MHz
54MHz
Crossover
Amplitude
7
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
AM Fiber Link
Diplex Filter
Forward Receiver
Forward Transmitter
Return Receiver
Return Transmitter
Forward Fiber
Return Fiber
AM Optical
Node
Hub or Headend
To/From
Distribution
System
8
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
RF Impulse-Pay-Per-View
AM Fiber Link
Coaxial Distribution
Drop
Settop
Terminal
Headend
Transport
Control
System
9
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
RF-IPPV Frequency Allocation
5 MHz
40 MHz
10 MHz
15 MHz
20 MHz
25 MHz
30 MHz
35 MHz
v
v
15.45MHz
17.75MHz
10
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
RF-IPPV Bandwidth Utilization
15.45 MHz
17.75 MHz
2.3MHz
23 Channel Slots
100kHz
11
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
High-Speed Cable Modems
AM Fiber Link
Coaxial Distribution
Drop
Settop
Terminal
Headend
Transport
Interface
12
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Cable Modem Frequency Allocation
5 MHz
40 MHz
10 MHz
15 MHz
20 MHz
25 MHz
30 MHz
35 MHz
13
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Cable Modem Bandwidth Utilization
5 MHz
40 MHz
10 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 Plant
Cable Telephony
Telephone
Interface
AM Fiber Link
Coaxial Distribution
Drop
Headend
Transport
Interface
15
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Cable Telephony Frequency Allocation
5 MHz
40 MHz
10 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 Plant
Cable Telephony Bandwidth Utilization
5 MHz
40 MHz
10 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 Plant
Status Monitoring
Monitoring
System
AM Fiber Link
Coaxial Distribution
Drop
Headend
Transport
18
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Status Monitoring Frequency Allocation
5 MHz
40 MHz
10 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 Plant
Status Monitoring Bandwidth Utilization
5 MHz
40 MHz
29.8MHz
250 kHz
20
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Interactive Services
Video Server
AM Fiber Link
Coaxial Distribution
Drop
Headend
Transport
Digital
Settop Terminal
21
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Interactive Services Frequency Allocation
• One or more channels
• Frequency Agile
5 MHz
40 MHz
10 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 Plant
Interactive Services Bandwidth Utilization
5 MHz
40 MHz
10 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 Plant
Current Bandwidth Utilization
5 MHz
40 MHz
10 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 Plant
Proposed Bandwidth Allocation
5 MHz
40 MHz
10 MHz
15 MHz
20 MHz
25 MHz
30 MHz
35 MHz
RF-IPPV
Telephony
Cable Modem
Status Monitoring
Interactive Services
25
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Bandwidth Limitations
5MHz
750MHz
Return
Forward
40MHz
54MHz
26
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Segmented Reverse
Fiber
Cable
Coaxial Distribution
Diplex Filter
Reverse Fiber Tx
Fiber Rx
27
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Block Conversion
Optical
Receiver
Optical
Transmitter
Block
Converter
Block
Converter
Combiner
54 MHz
750 MHz
Reverse Block
5 - 40MHz
Reverse Block
5 - 40MHz
Upstream Blocks
5 - 40 MHz
40 - 75 MHz
75 - 110 MHz
110 - 145 MHz
35 MHz
35 MHz
5
40
75
28
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
High-End Return
735 MHz
Forward
50 MHz
1 GHz
Return
900 MHz
29
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Thermal Noise
Carrier-to-Noise Ratio
Noise Energy
RF Carrier
30
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Noise Accumulation: Forward
1
2
4
5
3
31
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Noise Accumulation: Return
1
2
3
4
5
32
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Managing Thermal Noise
Return Transmitters
Return Combining
Network
Noise
33
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
RF Ingress
HAM
HAM
HAM
HAM
HAM
40 M
20 M
15 M
CB
Land
Mobile
40MHz
Land Mobile
Civil 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 Plant
Non-RF Ingress
Power line conducted
emissions and noise
Household electric
motor noise
Industrial electric
motor noise
Electrical switches
Electrostatic
discharge
35
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Ingress Causes
DropDrop
Reports of 70 to 90%caused by drops andhouse wiring.
10 to 30% caused bycoaxial plantproblems.
36
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Drop Cable
Transfer Impedance
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 Plant
RF Egress
Potential for Harmful Interference
HAM
HAM
HAM
HAM
HAM
40 M
20 M
15 M
CB
Land
Mobile
40MHz
Land Mobile
Civil Air Patrol
Civil Air Patrol
5.0MHz
Sub-Split Return Spectrum
38
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Rules 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
•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 Plant
Summary
•Bandwidth is limited and must be carefullymanaged
•Thermal Noise is a natural phenomenon and mustbe managed
•Ingress points must be located and eliminated ona continuous basis
•Egress must be tracked down and eliminated toprevent interference with radio communications
•Bandwidth is limited and must be carefullymanaged
•Thermal Noise is a natural phenomenon and mustbe managed
•Ingress points must be located and eliminated ona continuous basis
•Egress must be tracked down and eliminated toprevent interference with radio communications
40
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Basic 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 Plant
Headend
Pad
Modulator
Combiner
Same Amplitude
RF Carriers
To Distribution
42
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Forward 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 Plant
Forward Unity Transmission
-24
-24
-24
+24
+24
+24
+24
Condition
Established
Condition
Repeated
From
Headend
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 Plant
Basic Forward Amplifier
EQ
EQ
Interstage
Section
-20dB
Test
-20dB
Test
Input
Test Point
Output
Test Point
PAD
Input
Amp
Output
Amp
45
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Amplifier 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 Plant
Amplifier Pad
Input
Test Point
Input
Amp
+24dB
Desired Input = 11dBmV
Input = 16dBmV
5
Attenuation
24dB - 19dB = 5dB
Amplifier Output
11dBmV + 24dB = 35dBmV
-19dB
Amplifier Input
16dBmV - 5dB = 11dBmV
47
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Amplifier Pad Application
-24
-20
+24
+24
+24
+24
From
Headend
1
2
3
4
-22
5
-12
-11
Pad: 24 - 24 = 0
Input: 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 = 1
Input: 35 - 12 - 11 - 1 = 11
Pad: 24 - 20 = 4
Input: 35 - 20 - 4 = 11
Pad: 24 - 22 = 2
Input: 35 - 22 - 2 = 11
48
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Forward Amplifier Equalizer
EQ
EQ
Interstage
Section
-20dB
Test
-20dB
Test
Input
Test Point
Output
Test Point
PAD
Input
Amp
Output
Amp
49
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Cable Attenuation vs. Frequency
5
20
80
320
1280
1
2
4
8
16
4 x Frequency = 2 x Attenuation
4 x Frequency = 2 x Attenuation
Attenuation Factor
Frequency in MHz
50
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Cable Loss Ratio
50
800
50
800
Flat Test Signal
Cable = 24dB at 800MHz
6dB
24dB
51
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Equalizer Attenuation Curve
50
100
200
400
800
Attenuation
Frequency in MHz
Equalizer
Cable
Equalizer + Cable
52
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Equalizer Function
6dB
50MHz
100MHz
200MHz
400MHz
800MHz
8.5dB
16.5dB
13dB
12dB
17dB
8dB
19dB
1dB
Equalizer Attenuation
24dB
25dB
Cable Attenuation
25dB
25dB
25dB
53
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Equalizer Function
50
800
25dB
50
800
6dB
24dB
25dB
Equalizer
24dB
800MHz
Equalizer Input
Equalizer Output
Equalizer Reference Frequency
54
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Pad and Equalizer Practice
-24
-20
+24
+24
+24
+24
From
Headend
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 Plant
Transition to Tapped Feeder
-24
-20
+24
+24
From
Headend
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 Plant
Equal 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 Plant
Equal 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 Plant
Summary
•All signals aligned to common amplitude atHeadend
•The Forward Fiber Link provides “transparent”transport
•The Coaxial Trunk system provides “UnityTransmission”
•The Coaxial Feeder provides equal distribution ofavailable signal
•All signals aligned to common amplitude atHeadend
•The Forward Fiber Link provides “transparent”transport
•The Coaxial Trunk system provides “UnityTransmission”
•The Coaxial Feeder provides equal distribution ofavailable signal
59
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Basic 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 Plant
Signal Combining
Pad
Modulator
Combiner
Same Amplitude
RF Carriers
To Distribution
61
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Return Path as a Combiner
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Common
Test Point
Combiner
Settops
Objective: Achieve desiredamplitude and quality atcommon test point.
HFC Network
62
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Signal Combining at the Home
TV 1
TV 2
-5.5dB
75’ @ 1.67 = -1.25dB
35’ @ 1.67 = -.58dB
10’ @ 1.67 = -.17dB
+55
dBmV
+55
dBmV
1
2
3
49.3
48.9
48.3
+55
dBmV
Cable Modem
63
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Terminal Calibration
TV 1
TV 2
-5.5dB
75’ @ 1.67 = -1.25dB
35’ @ 1.67 = -.58dB
10’ @ 1.67 = -.17dB
+54
dBmV
+54.4
dBmV
1
2
3
48.3
48.3
48.3
+55
dBmV
Cable Modem
64
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Combining 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 = 24.5dB
Attenuation: 32dB
Reverse Amplifier Input
1:16.0dBmV4:20.5dBmV
2:17.5dBmV5:22.0dBmV
3:19.0dBmV6:23.5dBmV
1
2
3
4
5
6
1
2
3
4
5
6
65
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Traditional 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 = 24.5dB
Attenuation: 32dB
Reverse Amplifier Input = 16dBmV
1
2
3
4
5
6
6
5
4
3
2
1
Terminal output adjusted tocompensate for path conditions
66
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Unity Loss in Return Path
-.5
-.5
-.5
-.5
-.5
-1
-1
-1
-1
-1
-1
48
dBmV
48
dBmV
48
dBmV
48
dBmV
48
dBmV
48
dBmV
32
29
26
23
20
17
Reverse Amplifier Input
Uniform at 16.0dBmV
Maximum output level forbest carrier/interferenceratio
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 Plant
Splitters and DCs in the Return Path
-.5
-.5
-8
-.5
-.5
-1
-1
-1
-1
-1
-1
48
dBmV
48
dBmV
48
dBmV
48
dBmV
48
dBmV
48
dBmV
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
48
dBmV
48
dBmV
48
dBmV
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
68
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Basic Reverse Amplifier
EQ
EQ
Interstage
Section
-20dB
Test
-20dB
Test
Input
Test Point
Output
Test Point
PAD
Input
Amp
Output
Amp
Rvrs
Amp
Diplexer
Diplexer
-20dB
Test
-20dB
Test
EQ
EQ
PAD
-20dB
Rev Inj
69
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Reverse Pads and EQs
EQ
EQ
Interstage
Section
-20dB
Test
-20dB
Test
Input
Test Point
Output
Test Point
PAD
Input
Amp
Output
Amp
Rvrs
Amp
Diplexer
Diplexer
-20dB
Test
-20dB
Test
EQ
EQ
PAD
-20dB
Rev Inj
70
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Reverse Pad Application
-5
-8
+10
+10
To
Headend
+10
+10
-4
-2
+10
-5
-1
A
B
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 Plant
Reverse Pad Application (con’t)
-5
-8
+10
+10
To
Headend
+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
Amplifier #3 Input
0dB Pad
5dB Pad
1
2
3
A
B
72
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Reverse Pad Exercise
EQ
EQ
PAD
+10dB
+10dB
EQ
EQ
PAD
+10dB
+10dB
EQ
EQ
PAD
+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 Plant
Reverse Unity Transmission
-6
-6
-6
+6
+6
+6
+6
Condition
Established
Condition
Repeated
To
Headend
Gain = Loss
Output Level
Input Level
+6
-6
0
+6
-6
0
1
2
3
4
74
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Reverse Equalizers
EQ
EQ
Interstage
Section
-20dB
Test
-20dB
Test
Input
Test Point
Output
Test Point
PAD
Input
Amp
Output
Amp
Rvrs
Amp
Diplexer
Diplexer
-20dB
Test
-20dB
Test
EQ
EQ
PAD
-20dB
Rev Inj
75
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Cable Attenuation vs. Frequency
5
20
80
320
1280
1
2
4
8
16
4 x Frequency = 2 x Attenuation
4 x Frequency = 2 x Attenuation
Attenuation Factor
Frequency in MHz
76
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Cable Loss Ratio
50
800
50
800
Flat Test Signal
Cable = 24dB at 800MHz
6dB
24dB
77
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Equalizer Attenuation Curve
5
10
15
20
40
Attenuation
Frequency in MHz
Equalizer
Cable
Equalizer + Cable
78
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Reverse Equalizer Function
2.1dB
5MHz
10MHz
20MHz
40MHz
3dB
4dB
4.3dB
2.7dB
4.9dB
1dB
Equalizer Attenuation
6dB
Cable Attenuation
7dB
7dB
7dB
79
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Equalizer Function
5
40
7dB
5
40
2dB
6dB
7dB
Equalizer
6.0dB
40MHz
Equalizer Input
Equalizer Output
Equalizer Reference Frequency
80
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Reverse Pad and EQ Practice
-6
-5
+10
+10
+10
+10
To
Headend
-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 Plant
Reverse 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 Plant
Summary
•All paths must have equal attenuation
•Reverse signals must be maintained at thehighest possible levels
•40MHz signals experience only about one fourththe cable attenuation of 750MHz signals
•Passive devices attenuate forward and reversesignals approximately the same
•All paths must have equal attenuation
•Reverse signals must be maintained at thehighest possible levels
•40MHz signals experience only about one fourththe cable attenuation of 750MHz signals
•Passive devices attenuate forward and reversesignals approximately the same
83
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Early Return Path Application
2
T9
Video/Audioreturned toheadend on ReturnPath channel
Return Path Channeltranslated to ForwardPath channel
Subscribers view localvideo on Forward Pathchannel
84
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Basic Alignment Technique
Signal
Source
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 Plant
Improved Alignment Technique
2
Return Path signaldisplayed on analyzer
Technician views analyzerdisplay on TV and makesadjustments to ReturnPath
Spectrum
Analyzer
Baseband Video
Camera views analyzerdisplay
Camera outputmodulated to ForwardPath channel
Signal
Source
86
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Sweeping 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 Plant
Reverse Sweep Equipment
Headend Unit
Field Unit
88
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Typical Sweep Display
5MHz
40MHz
5db/Div
Ref Lvl +20dBmV
89
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Return 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 Plant
Installing the 3ST Transmitter
Combining Network
Forward
Laser
Forward
Laser
Return Path
Receiver
Return Path
Receiver
Return Signal Break-out
Diplex Filter
H / L
Fiber Out
Fiber In
out
in
Sweep Signal -10 to -12dB
Telemetry Signal -5dB
Input -10dBmVto +10dBmv
91
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Configuring 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 Plant
Sweeping a Fiber Node
Forward
Receiver
Forward
Receiver
Reverse
Transmitter
Reverse
Transmitter
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 Plant
Reverse Fiber Receivers
Return Path
Receiver
Return Path
Receiver
Return Signal Break-out
Diplex Filter
H / L
Fiber In
in
Return Path
Receiver
Return Path
Receiver
Fiber In
Return Path
Receiver
Return Path
Receiver
Fiber In
Return Path
Receiver
Return Path
Receiver
Fiber In
Return Signal Combiner
-8dB
-11dB
-0.5
-0.5
-0.5
+24dBmV
+3.5dBmV
94
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Inboard Test Points
LH
Coaxial
Cable
in
out
3SR
Forward Test Point
LH
Coaxial
Cable
Two-way Amplifier withTest Point Inboard ofDiplex Filter
95
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Outboard Test Points
LH
Coaxial
Cable
in
out
3SR
Forward Test Point
NS-6
LH
Coaxial
Cable
Two-way Amplifier withTest Point Outboard ofDiplex Filter
•Wavetek Model 3ST Operating Guide Section 5.1.3
96
GTS Enterprises, Inc.
Wednesday, September 18, 1996
Activating the Modern Return Plant
Summary
•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 transmittedsignals
•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 transmittedsignals