Transmission Line I

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A conductive connection that transfer electrical energy from one point to another.

Transmission Line

What connects your transceiver to your antenna?

Feed Line

______ waves travel from source to load while ______ waves travel back from load to source.

incident, reflected

______ line has two conductors with equal resistance while _____ line has one conductor connected to ground.

balanced, unbalanced

Balance Line has impedance from ____

150 Ω to 600 Ω

_____ current flow in opposite direction while ______ current flow in same direction

Metallic Circuit, Longitudinal

Open Wire Line has parallel conductor, closely spaced by _____ while Twin Lead or Ribbon Cable has parallel conductor, closely spaced by _____.

air, solid

The following are reasons to not use parallel conductor feed line except:

it works even there is high SWR.

What are the reasons to use parallel conductor feed line?

Any of these

What is used to couple coaxial cable to parallel lines?

Balun

Which transmission line is not used in high frequency?

Twisted Pair

Ushielded Twisted Pair has at least ____ twist per inch.

Which is used for voice grade and low speed data and has rate of 1 Mbps?

Cat 1

Cat 2 cable has rate reaching up to _____.

4 Mbps

Which cable reaches up to 16 Mbps?

Cat 3

Which cable reaches up to 20 Mbps?

Cat 3

Cat 3 has at least ___ turns per inch.

Which cable has rate of 20 Mbps?

Cat 4

Cat 5e has rate of _____ Mbps.

250

Which cable is known as Shielded Screen Twisted Pair?

Cat 7

___ consists of two copper wires encapsulated by PVC while STP has wires and dielectric enclosed in conductive metal sleeve.

UTP, STP

It is twisted pair with rate of 10 Mbps and span distance of 1200 meters.

RS 422A

The area between ceiling and roof or ceiling of next floor.

Plenum

It is non combustible tubing encasing riser cable.

Riser Conduit

Series of closets connected by slots between floors.

Raceway

What is commonly used transmission line?

Coaxial Cable

Coaxial Cable has conductor surrounded by ______ then shielding.

dielectric

Which can be buried directly in the ground for some distance without adverse effects?

Coaxial Cable

Coaxial Line is _____ line

unbalanced

Which is true about coaxial cable?

The impedance of a coaxial cable can be same for different diameter.

The characteristic impedance of a transmission line is:

equal to the pure resistance which, if connected to the end of the line, will absorb all the power arriving along it.

A transmission line differs from an ordinary circuit or network in communications or signaling devices in one very important way. That important aspect is:

propagation delay

The characteristic impedance of a parallel wire transmission line does not depend on the:

velocity of energy on the line

Any length of transmission line may be made to appear as an infinitely long line by:

terminating the line in its characteristic impedance

What factors determine the characteristic impedance of a parallel-conductor antenna feed line?

The distance between the centres of the conductors and the radius of the conductors

What factors determine the characteristic impedance of a coaxial antenna feed line?

The ratio of the diameter of the inner conductor to the diameter of the braid

What is a coaxial cable?

A center wire inside an insulating material which is covered by a metal sleeve or shield

What is parallel-conductor feed line?

Two wires side-by-side held apart by insulating rods

What kind of antenna feed line is made of two conductors held apart by insulated rods?

Open-conductor ladder line

Where would you install a balun to feed a dipole antenna with 50-ohm coaxial cable?

Between the coaxial cable and the antenna

A flexible coaxial line contains:

braid and insulation around a central conductor

A balanced transmission line:

is made of two parallel wires

A 75 ohm transmission line could be matched to the 300 ohm feedpoint of an antenna:

by using a 4 to 1 balun

What kind of antenna feed line can be constructed using two conductors which are maintained a uniform distance apart using insulated spreaders?

600 ohm open-wire

Why does coaxial cable make a good antenna feed line?

It is weatherproof, and its impedance matches most amateur antennas

What common connector usually joins RG-213 coaxial cable to an HF transceiver?

A PL-259 connector

What common connector usually joins a hand-held transceiver to its antenna?

A BNC connector

Which of these common connectors has the lowest loss at UHF?

A type-N connector

If you install a 6 metre Yagi antenna on a tower 50 metres from your transmitter, which of the following feed lines is best?

RG-213

Why should you regularly clean, tighten and re-solder all antenna connectors?

To help keep their resistance at a minimum

TV twin-lead feed line can be used for a feed line in an amateur station. The impedance of this line is approximately:

300 ohms

Why should you use only good quality coaxial cable and connectors for a UHF antenna system?

To keep RF loss low

If your transmitter and antenna are 15 metres apart, but are connected by 65 metres of RG-58 coaxial cable, what should be done to reduce feed line loss?

Shorten the excess cable

As the length of a feed line is changed, what happens to signal loss?

Signal loss increases as length increases

Losses occurring on a transmission line between transmitter and antenna results in:

less RF power being radiated

The lowest loss feed line on HF is:

open-wire

In what values are RF feed line losses expressed?

dB per unit length

If the length of coaxial feed line is increased from 20 metres (65.6 ft) to 40 metres (131.2 ft), how would this affect the line loss?

It would be increased by 100%

If the frequency is increased, how would this affect the loss on a transmission line?

It would increase

What does an SWR reading of 1:1 mean?

The best impedance match has been attained

What does an SWR reading of less than 1.5:1 mean?

A fairly good impedance match

What kind of SWR reading may mean poor electrical contact between parts of an antenna system?

A jumpy reading

What does a very high SWR reading mean?

The antenna is the wrong length, or there may be an open or shorted connection somewhere in the feed line

What does standing-wave ratio mean?

The ratio of maximum to minimum voltages on a feed line

If your antenna feed line gets hot when you are transmitting, what might this mean?

The SWR may be too high, or the feed line loss may be high

If the characteristic impedance of the feedline does not match the antenna input impedance then:

standing waves are produced in the feedline

The result of the presence of standing waves on a transmission line is:

reduced transfer of RF energy to the antenna

An SWR meter measures the degree of match between transmission line and antenna by:

comparing forward and reflected voltage

A resonant antenna having a feed point impedance of 200 ohms is connected to a feed line and transmitter which have an impedance of 50 ohms. What will the standing wave ratio of this system be?

4:1

The type of feed line best suited to operating at a high standing wave ratio is:

600 ohm open-wire

_____ coaxial cable has tubular outer conductor around a conductor and air insulation while _____ coaxial cable has braided, and flexible outer conductor.

Rigid, Solid

The following statement are disadvantage of rigid coaxial cable except:

It can minimize radiation losses

It is coaxial cable used for UHF connector.

PL-529

It is flat conductor separated from ground plane by dielectric.

Microstrip

Flat conductor sandwich between two ground planes.

Stripline

Dielectric constant of transmission line are:

inductance and capacitance

These are theoretical properties of a transmission line that are lumped into a single component.

Lumped Constant

Refers to penetration depth of current density from skin effect.

Skin Depth

It is potential difference between two conductors.

Dielectric Heating

What does Skin Effect cause?

Copper Loss

It is loss when current flows through a conductor.

Copper Loss

Self Induction retards the movement of the encircled electron in the center at above ___

100 MHz

Copper Loss can be minimized by:

plating the conductor with silver.

The loss when electrostatic and electromagnetic fields around conductor, and radiating.

Radiation Loss

It is luminous discharge between conductor when there is potential difference between them.

Corona

It is impedance seen looking at finite or infinite length terminated in purely resistive equal to characteristic impedance.

Surge Impedance

Capacitance and inductance of transmission line are ______

distributed

What happens to wire resistance and dielectric loss when frequency increases?

wire resistance and dielectric loss increases.

It deals with production, transport, and delivery of quality signal from source to destination.

Transmission System Engineering

It is used to calculate transmission line impedance.

Smith Chart

How is impedance represented on Smith Chart?

a point

______ is measure how voltage or current decreases with distance along with distance

Attenuation Constant

It express the attenuation and phase shift per length of transmission line.

Propagation Constant

It is difference in phase between input and output voltage or current.

Phase Constant

When load and line are mismatched,

power not absorbed will be reflected.

It is voltage and current variation along transmission line terminated with its characteristic impedance.

Standing Wave

Mismatching can be corrected by:

Any of these

If incident and reflected voltages are in phase are

maximum voltage and minimum current

If incident and reflected voltages are out of phase,

voltages neutralized

100

If a wire is terminated on short circuit, wire end is point of:

maximum current and zero voltage

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