hat is wave propagation?

Transmission of energy by electromagnetic radiation

What are the two electromagnetic fields associated with every antenna?

Induction and radiation fields

Basic antenna systems are composed of what two fields?

Electric and magnetic

What is electromagnetic radiation?

Radiation associated with periodically varying electric and magnetic fields

Electrical field exists around all _______________.

Electrically charged objects

In an electrical field lines travel from...

positive to negative

An electrical field is generated by ___________of antenna

capacitive action

In an electrical field lines connect....

at a right angle

An induction field continually...

expands and contracts

What type of combined field doesn't exist apart from the antenna?

Induction field

The direction of the magnetic field is determined by....

the direction of the current flow

Which field is represented by lines forming closed loops around a current-carrying conductor?

Magnetic (H) field

Which combined field is the action of the expanding and collapsing of the induction field causes radiation to be radiation to be released?

Radiation field

What are the two types of polarization?

Vertical and horizontal

Which type of polarization has an E field perpendicular to the Earth's surface?

Vertical

Which type of polarization is ideal for antennas at higher elevation?

Horizontal

Which type of polarization has an E field parallel to the Earth's surface?

Horizontal

Which type of polarization has the greater signal strength along the Earth's surface?

Vertical

Which polarization has the advantage of simple antenna?

Vertical

Which polarization has the less loss in dense areas?

Horizontal

Which polarization is affected less by reflection?

Vertical

Which polarization has the stronger receiver signal?

Vertical

Which polarization is the less likely to be affected by man-made interference?

Horizontal

Waves, light waves, radio waves, etc. are all types of ...

Electromagnetic energy

Radio waves have a shape that is similar to?

A sine wave

Electromagnetic waves travel

at the speed of light

What can likely slow down an electromagnetic wave?

Atmospheric conditions

What are wavelengths in Basic Antenna Systems?

The space occupied by one full cycle of a wave at any given instant

What are wavelengths measured in?

Meters

What are the two types of waves?

Ground waves and sky waves

What are the two types of ground waves?

Surface waves and direct waves

What are surface waves?

Waves that travel along the ground

What are direct waves?

Waves that travel from the transmitting to the receiving antenna.

What are sky waves?

Radio waves returned to Earth from the ionosphere

From the earth to space what is the order of regions of the atmosphere?

Troposphere, Stratosphere, and Ionosphere

What is reflection?

Turing back a wave from the boundary of a medium

Reflection can be reflected up to 180 degrees depending on...

The surface, angle of incidence, polarization, and wave length

What is refraction?

Changing direction of the wave as it passes through a medium

Refraction is dependent on...

Density of ionization of the layer, frequency of the radio wave, and the angle at which the wave enters the layer

What is defraction?

Bending of radio waves as they pass an object

Which propagation factor allows for receiving of radio waves around the edges of an obstacles?

Diffraction

What are antenna systems?

A conductor used to radiate or collect electromagnetic energy

What three basic components make up antenna systems?

Coupling device, feeder and antenna

The size and shape of an antenna system is determined by...

Frequency of transmitter, amount of power radiated, and the direction of the receiving antenna

What must be at least one-half the wavelength of the frequency?

Radiation of electromagnetic energy

What are the operational characteristics of antenna systems?

Reciprocity of antennas and antenna gain

What type of antenna is independent of ground?

Hertz

What are the four types of special antennas?

Long wire, Slot, Skin, and Blade

electromagnetic radiation

the radiation associated with an electric and magnetic field; it varies periodically

type of electromagnetic fields

Electric (E) field and Magnetic (H) field

Electric field

exist around all electrically charged objects. force of voltage on antenna.
lines travel from positive to negative and lines connect at right angles.

magnetic field

produced by current field through a conductor. direction is determined by flow current

Induction field

continually expands and collapses
doesn't exist apart from the antenna

radiation field

the action of the induction field expanding and collapsing causes the radiation field to be released

induction field and radiation field

associated with every antenna

Vertical Polarization

E Field perpendicular to earths surface
greater signal strength along Earth's surface

horizontal polarization

the E field is parallel to the earths surface.
ideal for antennas at higher elevation

advantages of vertical polarization

stronger antenna, stronger receiver signal up to 50 MHz, and affected less by reflection.

advantages of horizontal polarization

minimizes interference from certain directions, less likely to be affected by man-made interference, and less loss in dense areas.

electromagnetic energy

includes infrared waves, light waves, and radio waves

radio

radio waves in the 3 KHz to 300 MHz

frequencies (RF)

electromagnetic waves transmit electromagnetic energy through free spaces

radio waves shape

basic shape is that of a sine wave
may or may not retain shape once radiated into space

Radio Wave Velocity

electromagnetic waves travel at the speed of light
186,000 miles per second or 300,000 meters per second

what would slow down radio waves velocity

atmospheric conditions

radio wave wavelength

spaced occupied by one full cycle of a wave at any given instant
measured in meters

wave categories

ground wave and sky wave

ground wave

Radio waves that travel near the surface of the Earth

sky wave

Radio waves that are reflected back to Earth from the ionosphere
usually high frequency

Regions of the Atmosphere

troposphere, stratosphere, ionosphere

ionosphere

most important region for long distant point-to-point communication

Reflection

turning back of a wave from the boundary of a medium

Refraction

changing direction of the waves as it passes through a medium

Diffraction

bending of radio waves as they pass an object

Tropospheric Scattering

caused by turbulence in the troposphere

antenna system

a conductor used to radiate or collect electromagnetic energy

basic components of antenna systems

coupling, feeder, and antenna

antenna system size and shape

determined by frequency of transmitter, amount of power radiated, and direction of receiving antenna

Radiation of electromagnetic radiation

must be at least one-half the wavelength of the frequency

reciprocity of antennas

using one antenna for both transmission and reception

antenna gain

ration between directional propagation and total propagation

Hertz (Half Wave)

what type of antenna is independent of ground

marconi (quarter-waves)

grounded or connected to counterpoise, perpendicular to earth, one quarter wavelength, and resonates at same frequency as half-wave antenna

long wire antenna

at least one wavelength long, and used for frequencies up to twice that for which it was cut

slot antenna

radiator formed by narrow slot in metal surface. is one-half wavelength long. underside of a wing surface.

skin antenna

produced by flush-mounted antenna. electrically isolating portion of metal skin of the aircraft.

blade antenna

quarter-wave antenna fed through a base. low drag for external aircraft fuselage mounting.