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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

MEMIC

Mobile electromagnetic incompatibility
Caused by badly fitted radio in a vehicle
Vibrating radio in vehicle