Flashcards in Bandwidth And Modulation Deck (15):
0
What's bandwidth
Width of frequency covering a signal
1
What makes up a carrier wave
Audio frequency modulated with radio frequency which is modulated into
AM
FM
2
How many side bands does
AM
FM
AM has only an upper side band and lower side because it's uses only 1 frequency
FM has an infinite number of sidebands because it uses numerous frequencies
3
Why are channels split into 25khz
To allow for sidebands
4
USB
LSB
Upper sidebands
Lower sidebands
5
FM
Frequency modulation
Carrier wave remains constant
Very wide bandwidth
Infinite numbers of sidebands
Only used at VHF and above
Limits white noise to make it quieter
6
AM
Amplitude modulation
Only a single side band
White noise
Greater range than FM
Frequency remains constant
7
EMC
Electromagnetic compatibility is achieved when noise from external noises is kept to a minimum eg antenna siting
8
Environmental factors affecting noise
Atmospheric
Man made
Interference HF/UHF
9
Atmospheric noise increases
Tropical
Polar regions
Lower frequencies
Night
10
Man made noise
Unsurprised ignition systems
Generators
Telegraph lines
Trams
Trains
11
Counter measures for noise
Antenna siting
Suppres noise
Txing station increase power
Improve antenna efficiency
12
Interference
VHF
Super refracting
Ducting
Local mutual interference
Harmonics/breakthrough
HF
Local mutual interference
Ionospheric interference
13
Interference counter measures
VHF
Good freq assignment
Antenna siting
Minimum power
HF
Same as above
Ionospheric interference
14