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CETNetworking - BICSI - RCDD > CH 01 - Principles of Transmission > Flashcards

CH 01 - Principles of Transmission Flashcards

1
Q

What is the most common electrical conductors for ICT wire and cables?

A
  • Copper.
  • Copper-covered steel.
  • high-strength copper alloys.
  • Aluminum.
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2
Q

Copper:

A
  • Sets the standard for comparing the conductivity of other metals. Annealed copper is used as the reference value (eg. 100% Conductivity).
  • Good Ductility.
  • Good Solderability.
  • Good Corrosion Resistance.
  • Good Oxidation Resistance.
  • 1,001 ft of 10 AWG solid conductor weights 31.4 lbs.
  • Tensile Strength - 36,259 psi.
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3
Q

Cover Covered Steel:

A
  • Typically used as a conductor for aerial, self-supporting drop wire.
  • Good Ductility.
  • Good Solderability.
  • Good Corrosion Resistance.
  • Good Oxidation Resistance.
  • 1,001 ft of 10 AWG solid conductor weights 28.8 lbs.
  • Tensile Strength - 55,114 psi.
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4
Q

High Strength Copper Alloys:

A
  • A mixture of copper and other metals to improve certain copper alloy properties and characteristics of copper.
  • 85% conductivity rating.
  • Best Ductility.
  • Good Solderability.
  • Poor Corrosion Resistance.
  • Good Oxidation Resistance.
  • Tensile Strength - 79,771 psi.
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5
Q

Aluminum:

A
  • Bluish Silver-white malleable ductile.
  • Poor oxidation.
  • 60% conductivity rating.
  • Good Ductility.
  • Solderability requires special techniques.
  • Good Corrosion Resistance.
  • Poor Oxidation Resistance.
  • 1,001 ft of 10 AWG solid conductor weights 9.5 lbs.
  • Tensile Strength - 10,008 psi.
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6
Q

Advantages of solid conductors:

A
  • Less costly.
  • Less complex termination systems.
  • Better transmission performance at high frequencies.
  • Less resistance.
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7
Q

Advantages of stranded conductors:

A
  • More flexible.
  • Longer flex life.
  • Less susceptible to damage during crimp termination processes.
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8
Q

Composite conductor:

A

A term used to describe conductors constructed from non-traditional materials (eg. metallic resins, graphite).

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9
Q

Advantages of composite conductors:

A
  • Flexible.
  • Lightweight.
  • Inexpensive and easy to produce.
  • Easily embedded into other material.
  • Low coefficient of expansion.
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10
Q

Disadvantages of composite conductors:

A
  • Poor high attenuation analog transmission characteristics above 4,000 Hz.
  • Poor digital transmission characteristics.
  • Easily damaged unless encased in rigid material.
  • Inconsistent quality.
  • not recommended for use with modern telecommunications networks.
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11
Q

AWG

A
  • American Wire Gauge.

- AWG Sizing system has become generally accepted in North America.

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12
Q

Insulation

A
  • Insulation is used to isolate the flow of current by preventing direct contact between:
    • Conductors
    • A conductor and its environment.
  • Historically, telecommunications cable conductors were insulated with PVC and PE.
    • PVC was commonly used for ISP.
    • PE was commonly used for OSP.
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13
Q

Certain materials provide lower smoke and flame spread characteristics as well as improved transmission performance:

A
  • FEP (Fluorinated ethylene propylene) eg. Teflon®, NEOFLON FEP™)
  • ECTFE (Ethylene chlorotrifluoroethylene) eg. Halar®
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14
Q

FEP

A
  • Fluorinated ethylene propylene
  • Dielectric Constant: 2.1
  • Dissipation Factor: 0.0005
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15
Q

PE

A
  • Polyethylene
  • Dielectric Constant: 2.3
  • Dissipation Factor: ___
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16
Q

ECTFE

A
  • Ethylene chlorotrifluoroethylene
  • Dielectric Constant: 2.5
  • Dissipation Factor: 0.01
17
Q

PVC (non-plenum rated)

A
  • Polyvinyl Chloride
  • Dielectric Constant: 3.4
  • Dissipation Factor: ___
18
Q

PVC (plenum rated)

A
  • Polyvinyl Chloride
  • Dielectric Constant: 3.6
  • Dissipation Factor: 0.04
19
Q

XL Polyolefin

A
  • Cross Linked
  • Polyvinyl Chloride
  • Dielectric Constant: 3.8
  • Dissipation Factor: ___
20
Q

Dielectric Constant

A
  • The ratio of the capacitance of an insulated conductor to the capacitance of the same conductor uninsulated in the air. Air is the reference with a dialectric constant of 1.0.
  • Low dielectric constant is desirable.
21
Q

Dielectric Strength

A
  • Measures the maximum voltage that an insulation can withstand without breakdown.
  • A high value is preferred (withstand voltage stress)
22
Q

Dissipation Factor

A
  • The relative power loss in the insulation is due to molecular excitement and subsequent kinetic and thermal energy losses.
  • A low dissipation factor is preferable.
23
Q

IR

A
  • The insulation’s ability to resist the flow of current through it.
  • There is an inverse relationship between insulation resistance and cable length.
24
Q

Balanced Twisted Pair Overview

A
  • Metallic conductor cables commonly use balanced twisted-pair conduction.
  • The main reason for twisting pairs of conductors is to minimize crosstalk and noise by decreasing capacitance unbalance and mutual inductance coupling between pairs.
25
Q

Balanced Twisted Pair Overview

A
  • Twisting conductors improves the balance (physical symmetry) between conductors of a pair and reduces noise coupling from external noise sources.
  • Pair-to-pair capacitance unbalance is a 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. .
26
Q

Balanced Twisted Pair Overview

A
  • Mutual inductance is a measure of the 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.
  • The conditions under which crosstalk is measured include both capacitance unbalance and mutual inductance coupling effects.
27
Q

Pair Twists

A

Generally, a counterclockwise twist length between 50mm and 150 mm (1.97” and 6”) is used for voice and low-frequency data cables. Adjacent pairs are generally designed to have twist length differences of at least 12.7mm (.5”). These specifications vary according to the manufacturer.

28
Q

Tight Twisting

A
  • The option of tight twisting, where pair twist lengths are less than 12.7mm (.5”) is used particularly within and between computers and other data processing equipment.
  • Category 5e, category 6, category 6A and higher category cables employ tight twisting for optimum transmission performance.
29
Q

Environmental Consideration

A

Temperature Effects:

-One concern is the attenuation invrease at higher cable temperatures above 20C (68F).

CETNetworking - BICSI - RCDD (2 decks)

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