CH 01 - Principles of Transmission

Question 1

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

Answer 1

• Copper.
• Copper-covered steel.
• high-strength copper alloys.
• Aluminum.

Question 2

Copper:

Answer 2

• 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.

Question 3

Cover Covered Steel:

Answer 3

• 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.

Question 4

High Strength Copper Alloys:

Answer 4

• 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.

Question 5

Aluminum:

Answer 5

• 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.

Question 6

Advantages of solid conductors:

Answer 6

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

Question 7

Advantages of stranded conductors:

Answer 7

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

Question 8

Composite conductor:

Answer 8

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

Question 9

Advantages of composite conductors:

Answer 9

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

Question 10

Disadvantages of composite conductors:

Answer 10

• 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.

Question 11

AWG

Answer 11

• American Wire Gauge.

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

Question 12

Insulation

Answer 12

• 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.

Question 13

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

Answer 13

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

Question 14

FEP

Answer 14

• Fluorinated ethylene propylene
• Dielectric Constant: 2.1
• Dissipation Factor: 0.0005

Question 15

PE

Answer 15

• Polyethylene
• Dielectric Constant: 2.3
• Dissipation Factor: ___

Question 16

ECTFE

Answer 16

• Ethylene chlorotrifluoroethylene
• Dielectric Constant: 2.5
• Dissipation Factor: 0.01

Question 17

PVC (non-plenum rated)

Answer 17

• Polyvinyl Chloride
• Dielectric Constant: 3.4
• Dissipation Factor: ___

Question 18

PVC (plenum rated)

Answer 18

• Polyvinyl Chloride
• Dielectric Constant: 3.6
• Dissipation Factor: 0.04

Question 19

XL Polyolefin

Answer 19

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

Question 20

Dielectric Constant

Answer 20

• 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.

Question 21

Dielectric Strength

Answer 21

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

Question 22

Dissipation Factor

Answer 22

• 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.

Question 23

IR

Answer 23

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

Question 24

Balanced Twisted Pair Overview

Answer 24

• 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.

Question 25

Balanced Twisted Pair Overview

Answer 25

- 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. .

Question 26

Balanced Twisted Pair Overview

Answer 26

- 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.

Question 27

Pair Twists

Answer 27

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.

Question 28

Tight Twisting

Answer 28

- 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.

Question 29

Environmental Consideration

Answer 29

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