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TDMM - 001 - Principles of Transmission Flashcards

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1
Q

Chapter Overview

A

Main concepts related to signal transmission through metallic, optical fiber and wireless transmission media and current information related to POE

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2
Q

Balanced twisted pair transmission topics

A

Transmission fundamentals
Standards
Applications support
Performance and equipment compatibilityF

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3
Q

Fiber Topics

A

Transmission fundamentals
Standards
Applications support
preformance and equipment compatibility

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4
Q

Electrical Conductor

A

Any material that can carry an electric charge from one point to another

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5
Q

Common Electrical Conductors

A

Copper
Copper Covered Steel
Aluminum
Silver
Gold

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6
Q

Copper Types

A

paired conductor cabling
single conductor cabling (bonding and earthing)

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7
Q

Copper Covered Steel Types

A

Coaxial cable center conductors
Aerial Paired Drop Wire

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8
Q

Aluminum Types

A

Paired Cable Shielding
Coaxial cable outer shield conductors

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9
Q

Silver and Gold

A

Electrical conductors not used because of high cost

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10
Q

Annealed Copper

A

Reference value - 100 percent conductivity

Copper clad steel and aluminum have less than 100% annealed copper’s conductivity

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11
Q

Copper Covered Steel - Description

A

Combines conductivity of copper with the strength of steel

Aerial, self supporting drop wire

Copper layer bonded to steel core

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12
Q

Aluminum Description

A

Bluish, silver white malleable ductile light trivalent metallic element

Good electrical and thermal conductivity

high reflectivity

resistance to oxidation

60% conductivity compared with copper

lighter in weight than copper

Electrical Utility Distribution Lines - common use

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13
Q

Solid copper conductor properties

A

Electrical Conductivity - Base standard for conductive materials - 100%

Ductility - Good
Solderability - Good

Corrosion Resistance - Good

Oxidation Resistance - Good

Weight - 14.25 kg / 31.4 lb

Tensile Strength

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14
Q

Electrical Conductivity

A
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15
Q

Ductility

A
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16
Q

Solderability

A
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17
Q

Corrosion Resistance

A
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18
Q

Oxidation Resistance

A
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19
Q

Tensile Strength

A
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20
Q

Solid vs Stranded Conductors

A

Solid - Single piece of metal wire

Stranded - bundle together a number of small AWG solid conductors to create a single larger conductor

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21
Q

Solid Conductor Advantages

A

less costly
less complex termination
better transmission performance at high frequencies
less resistance

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22
Q

Stranded conductor advantages

A

more flexible
longer flex life
less susceptible to damage during crimp termination

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23
Q

Crimp Termination

A
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24
Q

American Wire Gauge - AWG

A

north america

standard reference for comparing various conductor materials

outside of the USA, typically metric

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25
AWG Number 4
0.204" 5.19mm
26
AWG Number 6
0.162" 4.11mm 13.3 mm2
27
AWG Number 8
0.128" 3.26mm 13.3 mm squared
28
AWG Number 10
0.102" 2.59mm 5.26 mm squared
29
AWG Number 12
0.0808" 2.05mm 3.31 mm sq
30
AWG Number 14
0.0641" 1.63mm 2.08mm sq
31
AWG Number 16
0.0508" 1.29mm 1.31 mmsq
32
AWG Number 18
0.0403" 1.02mm 0.823mm s
33
AWG Number 20
0.0320" 0.812mm 0.528 mm sq
34
Insulation
Used to isolate the flow of current by preventing direct contact between: Conductors Conductor and its inviromentI
35
Insulation Material
One or more plastic materials applied by a variety of methods
36
Extruded Polymer
Common insulation material proved to be functional, dependable and cost-effective
37
Insulation - Lower Dielectric Constant and Dissipation Factor
better transmission performance lower attenuation lower capacitance
38
Attenuation
39
Capacitance
40
Dielectrics
Reduce electromagnetic coupling between conductors by increasing conductor separation
41
Common insulators
PVC - Inside Plant PE - Outside Plant - better transmission, unsuitable for indoor use unless encased in fire-retardant jacket material
42
Insulators - lower smoke and flame spread characteristics + improved transmission performance
FEP - Teflon - NEOFLON FEP ECTFE - Halar
43
Insulator - Electrical Characteristics - FEP
Dielectric Constant - 2.1 Dissipation Factor - 0.0005
44
Insulator - Electrical Characteristics - PE
Dielectric Constant - 2.3 Dissipation Factor - n/a
45
Insulator - Electrical Characteristics - ECTFE
Dielectric Constant - 2.5 Dissipation Factor - 0.01
46
Insulator - Electrical Characteristics - PVC (Non-plenum)
Dielectric Constant - 3.4 Dissipation Factor - n/a
47
Insulator - Electrical Characteristics - PVC (Plenum)
Dielectric Constant - 3.6 Dissipation Factor - 0.04
48
Insulator - Electrical Characteristics - XL Polyolefin
Dielectric Constant - 3.8 Dissipation Factor - n/a
49
ECTFE
Ethylene chlorotrifluoroethylene
50
FEP
Fluorinated ethylene propylene
51
PE
Polyethylene
52
PVC
Polyvinyl Chloride
53
XL
Cross-linked
54
Dielectric Constant
The ratio of the capacitatnce of an insulated conductor to the capacitance of the same conductor uninsulated in the air air is the refernce with a dielectric constant of 1.0 a low dielectric constant is desirable changes with temperature, frequency and other factors
55
Dielectric Strength
Measures the maximum voltage that an insulation can withstand without breakdown Recorded in breakdown tests - voltage is increased at a controlled rate until the insulation fails. The voltage at that time, divided by the thickness of the insulation equals the dielectric strength expressed in V per mm High value preferred Typical strength of 7500 to 30,000 V per mm (for low voltage)
56
Insulator - Temperature Rising
ECTFE and FEP perform better than PVC as termperatures rise
57
Dissipation Factor
Relative power loss in the insulation due to molecular excitement and subsequent kinetic and thermal energy loses Primary concern in high-frequency MHz ranges where signal loss increases because of the structure of the insulating material Example Polar molecules (water) absorb energy in an electromagnetic field effect best understood in terms of microwave heating LOW dissipation factor is preferable
58
IR - (Insulation Resistance)
Insulation's ability to resist the flow of current through it Inside conductors - typically megohm * km or megohm * 1000ft Inverse relationship between insulation resistance and cable length (as cable length increases, insulation resistance becomes smaller)
59
Balanced Twisted Pair Cables
Twisting individual pairs and grouping those twisted pairs to form either a cable or a unit for larger cable Main Reason - minimize crosstalk and noise by decreasing capacitance unbalance and mutual inductance coupling between pairs. Improves balance (physical symmetry) between conductors Reduces noise coupling from external noise sources
60
Pair-to-Pair Capacitance Unbalance
Expressed in "picofarads per unit length" measure of the electric field coupling between two pairs if a differential voltage is applied on one pair and a differential noise voltage is measured on another pair in close proximity
61
Mutual Inductance
measure of magnetic field coupling between two pairs if a differential current is applied on one pair and a differential noise current is measured on another pair in close proximity
62
Crosstalk Measurement -
includes both capacitance unbalance and mutual inductance coupling effects
63
Differential Current
64
Differential Noise Current
P
65
Picofarad
66
Differential voltage
67
Differential Noise Voltage
68
Pair Twists
Both mutual inductance and capacitance unbalance are affected by the relative length and uniformity of pair twists Minimize crosstalk - within multipair cable, each pair is given a different twist length with a standard range
69
Counterclockwise Twist Length (Typical)
Between 50mm and 150mm Between 2" and 6"
70
Adjacent Pair Length Difference (Typical)
Adjacent pairs - differences of at least 13mm / 0.50"
71
Tight Twisting
Category 5e, 6, 6A employ tight twisting of individual pairs for optimum transmission performance Preserve shape better in a cable
72
Longer twists
nest together as packed in a cable
73
Electromagnetic Interference - EMI
Stray electrical energy radiated from electronic equipment and electronic systems cause distortion or interference to signals in other nearby cables or systems
74
Temperature Effects - Range -
20 / -3 : degree celcius 68 / -5.4 : degree fahrenheit
75
Temperature Effects - Locations
Exterior building walls ceiling spaces and plenums high levels of POE mechanical rooms
76
Temperature Effects - Attenuation Effects
Conductor Resistance Insulation dielectric constant Dissipation factor
77
Temperature Effects - Attenuation increase above 20C / 68F
0.2 percent per degree (screened cables)
78
Temperature Effects - Attenuation increase above 20-40C / 68-104F
0.4 percent per degree (unscreened cables)
79
Temperature Effects - Attenuation increase above 40-60C / 104-140F
0.6 percent per degree (unscreened cables)
80
Temperature Coefficient - Category 3 Cables
1.5 percent per degree Celsius
81
Temperature Effects - Insulators
Best Performing - FEP - Fluorinated Ethylene Propylene Average Performing - ECTFE - Ethylene chlorotrifuoroethylene Worst Performing - PVC - Polyvinyl Chloride
82
Cable Shielding
Metallic covering or envelope enclosing - Insulated conductor wire pair

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