Basic Radio Theory Flashcards
What is :
1-diffraction
2-critical angle
1-change in direction as a radio wave passes over Earth’s surface
2-angle at which radio wave leaves antenna
How are the electric and magnetic fields aligned in a vertically polarized antenna
Electric - vertical
Magnetic - horizontal
1-What is pulse modulation
2-what is pulse amplitude modulation (PAM)
3-what is pulse code modulation (PCM)
1-carrier transmitted in short pulses
2-amplitude of fixed series of pulses is modulated
3-each pulse amplitude is assigned either 1 or 0
How do FM transmitters differ from AM transmitters with regard to:
1-modulating power
2-reception
1-FM modulating power is lower
2-reception is static free
What is Depth of modulation
Extent to which carrier is modulated, expressed as percentage
What are sidebands
When rf carrier is AM, a single band of frequencies is produced above and below the carrier
Single Sideband Systems(SSB)
What is:
1-pilot carrier system
2-controlled carrier system
3-suppressed carrier system
1-a small carrier signal that is transmitted with the selected sideband, separated at receiver
2-carrier transmitted at full amplitude, between pauses in speech it is reduced
3-no carrier transmitted, all power contained in one sideband
What is a :
1-ground wave
2-direct wave
3-sky wave
1-a wave that follows Earth’s surface - VLF and HF
2-a wave that travels in straight lines - VHF and higher
3-waves refracted by ionosphere - HF
What are the 3 layers in the ionosphere
D layer
E / kenelley heaviside layer
F / Appleton layer
1-What properties does the ionosphere have during day
2-What properties does the ionosphere have during night
1-With large amount of UV radiation, abundance of free electrons
Said to be dense
All 3 layers present
2-less free electrons
Density decreases
D layer goes away, height of ionosphere increases
1-Does a radio wave have more/less refraction with a higher frequency
2-does the earth refract higher/lower frequencies during the day
1-Less
2- higher
What is :
1-skip distance
2-dead space
1-distance from transmitter to first touchdown point
2-distance between termination of ground wave and first touchdown point of sky wave
What is signal to noise ratio
A measure that compares level of desired signal to level of background noise
What frequency band is propagated as a space wave
VHF
What are 4 examples of directional antennas
Loop antenna
Parabolic antenna
Slotted planar antenna
Helical antenna
