Bandwidth And Modulation

Question 0

What makes up a carrier wave

Answer 0

Audio frequency modulated with radio frequency which is modulated into
AM
FM

Question 1

What’s bandwidth

Answer 1

Width of frequency covering a signal

Question 2

How many side bands does
AM
FM

Answer 2

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

Question 3

Why are channels split into 25khz

Answer 3

To allow for sidebands

Question 4

USB

LSB

Answer 4

Upper sidebands

Lower sidebands

Question 5

FM

Answer 5

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

Question 6

AM

Answer 6

Amplitude modulation
Only a single side band
White noise
Greater range than FM
Frequency remains constant

Question 7

EMC

Answer 7

Electromagnetic compatibility is achieved when noise from external noises is kept to a minimum eg antenna siting

Question 8

Environmental factors affecting noise

Answer 8

Atmospheric
Man made
Interference HF/UHF

Question 9

Atmospheric noise increases

Answer 9

Tropical
Polar regions
Lower frequencies
Night

Question 10

Man made noise

Answer 10

Unsurprised ignition systems
Generators
Telegraph lines
Trams
Trains

Question 11

Counter measures for noise

Answer 11

Antenna siting
Suppres noise
Txing station increase power
Improve antenna efficiency

Question 12

Interference

Answer 12

VHF
Super refracting
Ducting
Local mutual interference 
Harmonics/breakthrough 
HF
Local mutual interference
Ionospheric interference

Question 13

Interference counter measures

Answer 13

VHF
Good freq assignment
Antenna siting
Minimum power
 HF
Same as above
Ionospheric interference

Question 14

MEMIC

Answer 14

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