Survey Maker Survey Templates Contact Privacy & Security

Exam Primer Transmission Line Part 1

What connects your transceiver to your antenna?

The power cord

A ground wire

A feed line

A dummy load

The characteristic impedance of a transmission line is determined by the:

Length of the line

Physical dimensions and relative positions of the conductors

Frequency at which the line is operated

Load placed on the line

The characteristic impedance of a 20 metre piece of transmission line is 52 ohms. If 10 metres were cut off, the impedance would be:

52 ohms

26 ohms

39 ohms

13 ohms

The impedance of a coaxial line:

Changes with the frequency of the energy it carries

Is correct for only one size of line

Is greater for larger diameter line

Can be the same for different diameter line

What commonly available antenna feed line can be buried directly in the ground for some distance without adverse effects?

300 ohm twin-lead

600 ohm open-wire

75 ohm twin-lead

Coaxial cable

The characteristic impedance of a transmission line is:

The impedance of a section of the line one wavelength long

The dynamic impedance of the line at the operating frequency

The ratio of the power supplied to the line to the power delivered to the termination

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:

Capacitive reactance

Inductive reactance

Propagation delay

Resistance

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

Velocity of energy on the line

Radius of the conductors

Centre to centre distance between conductors

Dielectric

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

Terminating the line in its characteristic impedance

Leaving the line open at the end

Increasing the standing wave ratio above unity

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

The distance between the centres of the conductors and the length of the line

The radius of the conductors and the frequency of the signal

The frequency of the signal and the length of the line

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

The diameter of the braid and the length of the line

The diameter of the braid and the frequency of the signal

The frequency of the signal and the length of the line

What is a coaxial cable?

Two wires side-by-side in a plastic ribbon

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

Two wires twisted around each other in a spiral

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

What is parallel-conductor feed line?

Two wires twisted around each other in a spiral

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

A metal pipe which is as wide or slightly wider than a wavelength of the signal it carries

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

Coaxial cable

Twin lead in a plastic ribbon

Twisted pair

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

Between the coaxial cable and the antenna

Between the transmitter and the coaxial cable

Between the antenna and the ground

Between the coaxial cable and the ground

What is an unbalanced line?

Feed line with neither conductor connected to ground

Feed line with both conductors connected to ground

Feed line with both conductors connected to each other

Feed line with one conductor connected to ground

What device can be installed to feed a balanced antenna with an unbalanced feed line?

A triaxial transformer

A balun

A wavetrap

A loading coil

A flexible coaxial line contains:

Four or more conductors running parallel

Only one conductor

Braid and insulation around a central conductor

Two parallel conductors separated by spacers

A balanced transmission line:

Is made of two parallel wires

Has one conductor inside the other

Carries RF current on one wire only

Is made of one conductor only

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

With an extra 250 ohm resistor

By using a 4 to 1 balun

By using a 4 to 1 trigatron

By inserting a diode in one leg of the antenna

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

Coaxial cable

75 ohm twin-lead

600 ohm open-wire

300 ohm twin-lead

Why does coaxial cable make a good antenna feed line?

It is weatherproof, and its impedance is higher than that of most amateur antennas

It is weatherproof, and its impedance matches most amateur antennas

It can be used near metal objects, and its impedance is higher than that of most amateur antennas

You can make it at home, and its impedance matches most amateur antennas

What is the best antenna feed line to use, if it must be put near grounded metal objects?

Ladder-line

Twisted pair

Coaxial cable

Twin lead

What are some reasons not to use parallel-conductor feed line?

You must use an impedance-matching device with your transceiver, and it does not work very well with a high SWR

It does not work well when tied down to metal objects, and it cannot operate under high power

It does not work well when tied down to metal objects, and you must use an impedance- matching device with your transceiver

It is difficult to make at home, and it does not work very well with a high SWR

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

A PL-259 connector

An F-type cable connector

A banana plug connector

A binding post connector

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

A BNC connector

A PL-259 connector

An F-type cable connector

A binding post connector

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

An F-type cable connector

A BNC connector

A PL-259 connector

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-174

RG-59

RG-213

RG-58

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

To help keep their resistance at a minimum

To keep them looking nice

To keep them from getting stuck in place

To increase their capacitance

What commonly available antenna feed line can be buried directly in the ground for some distance without adverse effects?

75 ohm twin-lead

600 ohm open-wire

Coaxial cable

300 ohm twin-lead

When antenna feed lines must be placed near grounded metal objects, which of the following feed lines should be used?

300 ohm twin-lead

600 ohm open-wire

75 ohm twin-lead

Coaxial cable

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

600 ohms

50 ohms

300 ohms

70 ohms

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

To keep television interference high

To keep the power going to your antenna system from getting too high

To keep the standing wave ratio of your antenna system high

To keep RF loss low

What are some reasons to use parallelconductor feed line?

It will operate with a high SWR, and has less loss than coaxial cable

It has low impedance, and will operate with a high SWR

It will operate with a high SWR, and it works well when tied down to metal objects

It has a low impedance, and has less loss than coaxial cable

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 so the feed line is an odd number of wavelengths long

Shorten the excess cable

Roll the excess cable into a coil which is as small as possible

Shorten the excess cable so the feed line is an even number of wavelengths long

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

Signal loss decreases as length increases

Signal loss increases as length increases

Signal loss is the least when the length is the same as the signal's wavelength

Signal loss is the same for any length of feed line

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

Signal loss increases with decreasing frequency

Signal loss increases with increasing frequency

Signal loss is the least when the signal's wavelength is the same as the feed line's length

Signal loss is the same for any frequency

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

An SWR reading of 1:1

Less RF power being radiated

Reflections occurring in the line

The wire radiating RF energy

The lowest loss feed line on HF is:

Open-wire

75 ohm twin-lead

Coaxial cable

300 ohm twin-lead

In what values are RF feed line losses expressed?

Ohms per MHz

DB per MHz

Ohms per metre

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%

It would be reduced by 10%

It would be increased by 10%

It would be reduced to 50%

If the frequency is increased, how would this affect the loss on a transmission line? (Answer bank has it wrong. Answer should be: It would increase)

It is independent of frequency

It would increase

It depends on the line length

It would decrease

What does an SWR reading of 1:1 mean?

The best impedance match has been attained

An antenna for another frequency band is probably connected

No power is going to the antenna

The SWR meter is broken

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

A fairly good impedance match

An impedance match which is too low

An impedance mismatch; something may be wrong with the antenna system

An antenna gain of 1.5

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

A negative reading

No reading at all

A jumpy reading

A very low reading

What does a very high SWR reading mean?

The transmitter is putting out more power than normal, showing that it is about to go bad

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

There is a large amount of solar radiation, which means very poor radio conditions

The signals coming from the antenna are unusually strong, which means very good radio conditions

What does standing-wave ratio mean?

The ratio of maximum to minimum voltages on a feed line

The ratio of maximum to minimum inductances on a feed line

The ratio of maximum to minimum resistances on a feed line

The ratio of maximum to minimum impedances on a feed line

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

You should transmit using less power

The conductors in the feed line are not insulated very well

The feed line is too long

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:

Heat is produced at the junction

The SWR reading falls to 1:1

The antenna will not radiate any signal

Standing waves are produced in the feedline

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

Perfect impedance match between transmitter and feedline

Maximum transfer of energy to the antenna from the transmitter

Lack of radiation from the transmission line

Standing waves are produced in the feedline

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

Perfect impedance match between transmitter and feedline

Maximum transfer of energy to the antenna from the transmitter

Lack of radiation from the transmission line

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

Measuring radiated RF energy

Measuring the conductor temperature

Inserting a diode in the feed line

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?

6:1

3:1

4:1

5:1

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

75 ohm twin-lead

600 ohm open-wire

Coaxial line

300 ohm twin-lead

What device might allow use of an antenna on a band it was not designed for?

An antenna tuner

An SWR meter

A low pass filter

A high pass filter

What does an antenna matching unit do?

It matches a transceiver to a mismatched antenna system

It helps a receiver automatically tune in stations that are far away

It switches an antenna system to a transmitter when sending, and to a receiver when listening

It switches a transceiver between different kinds of antennas connected to one feed line

What would you use to connect a coaxial cable of 50 ohms impedance to an antenna of 35 ohms impedance?

An SWR meter

An impedance-matching device

A low pass filter

A terminating resistor

When will a power source deliver maximum output to the load?

When air wound transformers are used instead of iron-core transformers

When the power-supply fuse rating equals the primary winding current

When the impedance of the load is equal to the impedance of the source

When the load resistance is infinite

What happens when the impedance of an electrical load is equal to the internal impedance of the power source?

The electrical load is shorted

The source delivers maximum power to the load

No current can flow through the circuit

The source delivers minimum power to the load

Why is impedance matching important?

So the load will draw minimum power from the source

To ensure that there is less resistance than reactance in the circuit

To ensure that the resistance and reactance in the circuit are equal

So the source can deliver maximum power to the load

To obtain efficient power transmission from a transmitter to an antenna requires:

High load impedance

Low ohmic resistance

Matching of impedances

Inductive impedance

To obtain efficient transfer of power from a transmitter to an antenna, it is important that there is a:

High load impedance

Matching of impedance

Proper method of balance

Low ohmic resistance

If an antenna is correctly matched to a transmitter, the length of transmission line:

Must be a full wavelength long

Must be an odd number of quarter-wave

Must be an even number of half-waves

Will have no effect on the matching

The reason that an RF transmission line should be matched at the transmitter end is to:

Ensure that the radiated signal has the intended polarization

Transfer the maximum amount of power to the antenna

Prevent frequency drift

Overcome fading of the transmitted signal

If the centre impedance of a folded dipole is approximately 300 ohms, and you are using RG8U (50 ohms) coaxial lines, what is the ratio required to have the line and the antenna matched?

2:1

4:1

10:1

6:1

{"name":"Exam Primer Transmission Line Part 1", "url":"https://www.quiz-maker.com/QPREVIEW","txt":"What connects your transceiver to your antenna?, The characteristic impedance of a transmission line is determined by the:, The characteristic impedance of a 20 metre piece of transmission line is 52 ohms. If 10 metres were cut off, the impedance would be:","img":"https://www.quiz-maker.com/3012/images/ogquiz.png"}