Radio Waves Flashcards
the physical interaction among electric charges, magnetic moments, and the electromagnetic field.
Electromagnetism
Electromagnetic waves are generally known as ________ and obey the laws of _______.
light, optics
a measurement of how often a recurring event such as a wave occurs in a measured amount of time
Frequency
One completion of the repeating pattern is called a
cycle
The distance from the “crest” (top) of one wave to the crest of the next wave is
the wavelength
Energy in the form of wave
Electromagnetic radiation
Light travels in _______ line, at a ________speed, in the form of _______
straight, constant, wave
The existence of radio waves was proved by __________ in the year ______
Heinrich Hertz, 1880
The basic building block of radio communication
radio wave
Radio waves are a form of radiation known as electromagnetic waves. The wavelength of radio waves is longer than the infrared light.
Property 1
Radio waves can travel for a long distance.
Property 2
Radio waves can penetrate through materials.
Property 3
Radio waves cannot be felt and they are invisible.
Property 4
They travel at the speed of light in vacuum. When they travel through the materials the speed differs, depending on the object’s permeability and permittivity.
Property 5
The wavelength range of radio waves is from thousands of metres to 30 mm. These correspond to a frequency from 3 Hertz to 109Hertz.
Property 6
Radio waves are emitted naturally by lightning and astronomical objects that have a changing magnetic field. They are also created by varying electric currents.
Property 7
Radio waves experience reflection, refraction, absorption, diffraction and polarisation.
Property 8
Radio waves have both electric and magnetic components.
Property 9
Formula for frequency
F = 1/T
For the generation of radio waves, _____________ radiate EM energy
Accelerating charges
For the generation of radio waves, If charges oscillate back and forth, It gets _________ too.
time-varying magnetic fields
Amplitude Modulation (AM) that uses changes in the __________ to convey information
signal strength
AM Radio uses frequency range from
530 kHz to 1700 kHz
Frequency Modulation (FM) uses changes in the ____________ to convey information
wave’s frequency
FM radio Spans __________ in 200 kHz intervals
87.8 MHz to 108.0 MHz
Communication radios in general aviation aircraft use a portion of __________________, with frequencies between _______ to ______
the very high frequency (VHF) range, 118.0 MHz to 135.975 MHz
the bent whip rods mounted on top of the cabin
VHF antennas
Range of VHF transmissions is limited to
line of sight (obstructions such as buildings, terrains and the curvature of the earth block the radio waves)
Radios are classified according to number of channels they can accommodate: ____-channel radio or ____-channel radio
320 or 720
Since the communication radios usually combine a transmitter and a receiver, they are called ________
transceivers
