Reviewer in Radiation and Wave Propagation | ECE Board Exam

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(Last Updated On: February 15, 2020)

Review Notes in Radiation and Wave Propagation

This is the Reviewer in Radiation and Wave Propagation as one topic in ECE Board Exam taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies (EST), Communications Books, Journals and other Communications References. This particular Coaching Notes in Communications Engineering has random Questions and Answers in random topics. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.

Summary of Important Radiation and Wave Propagation Review Notes

Field strength is the amount of voltage induced in a wave by an electromagnetic wave

An electromagnetic wave consists of both electric and magnetic fields

 

D is the lowest layer of the ionosphere

James Clerk Maxwell profounded electromagnetic radiation theory

The D, E and F layers are known as Kennely-Heaviside layers

 

Band – different grouping of the electromagnetic spectrum

90° is the relation in degrees of the electric and magnetic fields in an electromagnetic wave

A changing electric field gives rise to a magnetic field

Frequencies in the UHF range propagate by means of space waves

In electromagnetic waves, polarization is due to the transverse nature of the waves

Electromagnetic waves are refracted when they pass into a medium of different dielectric constants

Ionosphere is the highest layer of the atmosphere

F2 is the thickest layer of the ionosphere

K factor – Effective earth radius to true earth radius ratio

Reflection-multipath – fading due to interference between direct and reflected rays

D layer reflects very low frequency waves and absorbs medium frequency waves

E layer is used for high-frequency daytime propagation

Critical frequency is the highest frequency that can be sent straight upward and be returned to earth

High frequency range is from 3 to 30 MHz

 

Medium frequency range is from 0.3 to 3 MHz

 

In tropospheric scatter propagation, the attenuation is dependent on scatter angle

If the transmitter power remains constant, an increase in the frequency of the sky wave will lengthen the skip distance

The unit of electric field strength is volts per meter

Polarization refers to the direction of the electric field vector space

Circularly polarized – a TEM wave whose polarization rotates

300 x 10^6 m/s – velocity of light in free spaces

Radiowave that is far from its sources is called plane wave

Light goes from medium A to medium B at angle of incidence of 40°. The angle of refraction is 30°. The speed of light in B is less than that in A

In a vacuum the speed of an electromagnetic wave is a universal constant

 

The depth of an object submerged in a transparent liquid always seems less than its actual depth

Wavefront – a fixed point in an electromagnetic wave

VHF ship station transmitters must have the capability of reducing carrier power to 1 W

 

Most of the effects an electromagnetic wave produces when it interacts with matter are due to its electric field

 

A mobile receiver experiences “dead” areas of reception as a result of shading of the RF signal by hills and trees

 

When the electric field is perpendicular to the surface of the earth, vertical is the polarization of the TEM wave

When the magnetic field is perpendicular to the surface of the earth, horizontal is the polarization of the TEM wave

When the magnetic field is parallel to the surface of the earth, vertical is the polarization of the TEM wave

The two interrelated fields considered to make up an electromagnetic wave are an electric field and a magnetic field

 

The bandwidth of the transmitted signal affect selective fading because it is more pronounced at wide bandwidths

Spread spectrum communication – a wide bandwidth communications system in which the RF carrier varies according to some predetermined sequence

A changing magnetic field gives rise to electric field

When a space-wave signal passes over a mountain ridge, a small part of the signal is diffracted down the far side of the mountain. This phenomenon is called knife-edge diffraction

The index of refraction of a material medium is greater than 1

Electromagnetic waves travel in free space approximately 300 million meters per second

Vertical polarization – electric field that lies in a plane perpendicular to the earth’s surface

Horizontal polarization – electric field that lies in a plane parallel to the earth’s surface

Fading applies to troposcatter propagation

VLF waves are used for some types of service because they are very reliable

High-frequency waves are affected by the solar cycle

Distances near the skip distance should be used for sky-wave propagation to prevent sky-wave and upper ray interference

A ship-to-ship communications system is plagued by fading. The best solution seems to be the use of frequency diversity

A range of microwave frequencies more easily passed by the atmosphere than are the other is called a window

Frequencies in the UHF range normally propagate by means of space waves

Tropospheric scatter is used with frequencies in the UHF range

The ground wave eventually disappears as one moves away from the transmitter, because of tilting

In electromagnetic waves, polarization means the physical orientation of electric field in space

As electromagnetic waves travel in free space, attenuation happens

The absorption of a radio waves by the atmosphere depends on their frequency

Diffraction of electromagnetic waves may occur around the edge of a sharp obstacle

In an electromagnetic wave the electric field is perpendicular to both the magnetic field and the wave direction

The highest frequencies are found in x-rays

Electromagnetic waves transport energy

 

The ionosphere is a region of ionized gas in the upper atmosphere. The ionosphere is responsible for long-distance radio communications

 

Blue – light of which has the shortest wavelength

The quality in sound that corresponds to color in light is pitch

All real images can appear on a screen

 

When a beam of light enters on medium from another, a quality that never changes is its frequency

 

Relative to the angle of incidence, the angle of refraction is smaller or is larger

 

A light ray enters one medium from another along the normal. The angle of refraction is dependent on the indexes of refraction of the two media

 

E layer aids MF surface-wave propagation a little and reflects some HF waves in daytime

Dispersion is the term used to describe the splitting of white light into its component colors in refraction

 

The depth of an objects submerged in a transparent liquid always seems less than its actual depth

Total internal reflection can occur when light passes from one medium to another that has a lower index of refraction

When a light ray approaches a glass-air interface from the glass side at the critical angle, the angle of refraction is 90°

The brightness of light source is called its luminous intensity, whose unit is candela

Luminous efficiency is least for a low-wattage light bulb

The minimum illumination recommended for reading is 8000 lx

The solid angle subtended by a hemisphere about its center is 2π sr

Microwave signals propagate by way of the direct wave

The ionosphere causes radio signals to be refracted

Groundwave communications is most effective in 300 kHz to 3 MHz frequency range

The ionosphere has its greatest effect on signals in 3 to 30 MHz frequency range

The type of radio wave responsible for long-distance communication by multiple skips is the sky wave

Line-of-sight communications is not a factor in HF frequency range

A microwave-transmitting antenna is 550 ft. high. The receiving antenna is 200 ft high. The minimum transmission distance is 53.3 mi

To increase the transmission distance of UHF signal, increase antenna height should be done

Inverse Square Law – states that power density is inversely proportional to the distance from its source

Sky wave gets in contact with the ionosphere and reflected by it

F2 is the highest layer in the ionosphere

E is the next lowest layer in the ionosphere

Ultraviolet radiation is the primary cause of ionization in the atmosphere

F2 layers does not disappear at night

ELF, VLF and MF use surface wave propagation

The ability of the ionosphere to reflect a radio wave back to the earth is determined by operating frequency, ion density and angle of incidence

MUF – highest frequency that can be used for skywave propagation between two given points on earth

Skip distance – the shortest distance measured along the earth’s surface that a skywave is returned to earth

Fading – fluctuations in the signal strength at the receiver

Space diversity – two or more antennas are used separated by several wavelengths

Frequency diversity – two or more receivers are used using a single antenna

Diversity is not a cause of fading

Solar flares – the gigantic emission of hydrogen from the sun

SIDs – Sudden Ionospheric Disturbance

Troposcatter propagation – a means of beyond the line of sight propagation of UHF signals

Troposcatter – two directional antennas are pointed so that their beams intersect in the troposhere

Ducting – super refraction

Duct – a layer of warm air trapped above cooler air

Electric field corresponds to voltage

Shadow zone – absence of reception

Huygen’s principle – each point on a spherical waveform maybe a source of a secondary spherical wavefront

Ducting occurs in Troposphere

E region is most ionized at midday

Transequatorial propagation is best during afternoon or early evening

 

Very high and ultra high frequencies is most affected by knife-edge refraction

F2 layer has an average height of 225 km at night

Complete List of Communications Engineering Review Notes

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