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ICT > TDMM - 001 - Principles of Transmission > Flashcards

TDMM - 001 - Principles of Transmission Flashcards

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
Q

AWG Number 4

A

0.204”

5.19mm

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26
Q

AWG Number 6

A

0.162”

4.11mm

13.3 mm2

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27
Q

AWG Number 8

A

0.128”

3.26mm

13.3 mm squared

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28
Q

AWG Number 10

A

0.102”

2.59mm

5.26 mm squared

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29
Q

AWG Number 12

A

0.0808”

2.05mm

3.31 mm sq

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30
Q

AWG Number 14

A

0.0641”

1.63mm

2.08mm sq

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31
Q

AWG Number 16

A

0.0508”

1.29mm

1.31 mmsq

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32
Q

AWG Number 18

A

0.0403”

1.02mm

0.823mm s

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33
Q

AWG Number 20

A

0.0320”

0.812mm

0.528 mm sq

34
Q

Insulation

A

Used to isolate the flow of current by preventing direct contact between:
Conductors
Conductor and its inviromentI

35
Q

Insulation Material

A

One or more plastic materials applied by a variety of methods

36
Q

Extruded Polymer

A

Common insulation material

proved to be functional, dependable and cost-effective

37
Q

Insulation - Lower Dielectric Constant and Dissipation Factor

A

better transmission performance
lower attenuation
lower capacitance

38
Q

Attenuation

A
39
Q

Capacitance

A
40
Q

Dielectrics

A

Reduce electromagnetic coupling between conductors by increasing conductor separation

41
Q

Common insulators

A

PVC - Inside Plant

PE - Outside Plant - better transmission, unsuitable for indoor use unless encased in fire-retardant jacket material

42
Q

Insulators - lower smoke and flame spread characteristics + improved transmission performance

A

FEP - Teflon - NEOFLON FEP

ECTFE - Halar

43
Q

Insulator - Electrical Characteristics - FEP

A

Dielectric Constant - 2.1

Dissipation Factor - 0.0005

44
Q

Insulator - Electrical Characteristics - PE

A

Dielectric Constant - 2.3

Dissipation Factor - n/a

45
Q

Insulator - Electrical Characteristics - ECTFE

A

Dielectric Constant - 2.5

Dissipation Factor - 0.01

46
Q

Insulator - Electrical Characteristics - PVC (Non-plenum)

A

Dielectric Constant - 3.4

Dissipation Factor - n/a

47
Q

Insulator - Electrical Characteristics - PVC (Plenum)

A

Dielectric Constant - 3.6

Dissipation Factor - 0.04

48
Q

Insulator - Electrical Characteristics - XL Polyolefin

A

Dielectric Constant - 3.8

Dissipation Factor - n/a

49
Q

ECTFE

A

Ethylene chlorotrifluoroethylene

50
Q

FEP

A

Fluorinated ethylene propylene

51
Q

PE

A

Polyethylene

52
Q

PVC

A

Polyvinyl Chloride

53
Q

XL

A

Cross-linked

54
Q

Dielectric Constant

A

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
Q

Dielectric Strength

A

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
Q

Insulator - Temperature Rising

A

ECTFE and FEP perform better than PVC as termperatures rise

57
Q

Dissipation Factor

A

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
Q

IR - (Insulation Resistance)

A

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
Q

Balanced Twisted Pair Cables

A

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
Q

Pair-to-Pair Capacitance Unbalance

A

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
Q

Mutual Inductance

A

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
Q

Crosstalk Measurement -

A

includes both capacitance unbalance and mutual inductance coupling effects

63
Q

Differential Current

A
64
Q

Differential Noise Current

A

P

65
Q

Picofarad

A
66
Q

Differential voltage

A
67
Q

Differential Noise Voltage

A
68
Q

Pair Twists

A

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
Q

Counterclockwise Twist Length (Typical)

A

Between 50mm and 150mm
Between 2” and 6”

70
Q

Adjacent Pair Length Difference (Typical)

A

Adjacent pairs - differences of at least 13mm / 0.50”

71
Q

Tight Twisting

A

Category 5e, 6, 6A employ tight twisting of individual pairs for optimum transmission performance

Preserve shape better in a cable

72
Q

Longer twists

A

nest together as packed in a cable

73
Q

Electromagnetic Interference - EMI

A

Stray electrical energy radiated from electronic equipment and electronic systems

cause distortion or interference to signals in other nearby cables or systems

74
Q

Temperature Effects - Range -

A

20 / -3 : degree celcius
68 / -5.4 : degree fahrenheit

75
Q

Temperature Effects - Locations

A

Exterior building walls
ceiling spaces and plenums
high levels of POE
mechanical rooms

76
Q

Temperature Effects - Attenuation Effects

A

Conductor Resistance

Insulation dielectric constant

Dissipation factor

77
Q

Temperature Effects - Attenuation increase above 20C / 68F

A

0.2 percent per degree (screened cables)

78
Q

Temperature Effects - Attenuation increase above 20-40C / 68-104F

A

0.4 percent per degree (unscreened cables)

79
Q

Temperature Effects - Attenuation increase above 40-60C / 104-140F

A

0.6 percent per degree (unscreened cables)

80
Q

Temperature Coefficient - Category 3 Cables

A

1.5 percent per degree Celsius

81
Q

Temperature Effects - Insulators

A

Best Performing - FEP - Fluorinated Ethylene Propylene

Average Performing - ECTFE - Ethylene chlorotrifuoroethylene

Worst Performing - PVC - Polyvinyl Chloride

82
Q

Cable Shielding

A

Metallic covering or envelope enclosing -
Insulated conductor wire pair

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