2. WHAT IS FREQUENCY
Frequency is the rate at which occurs over a particular time
The rate per second of a vibration constituting a wave
‘A’ note on a violin string vibrates at about 440 Hz (440
vibrations per second)
It is measured in the hertz unit
The hertz abbreviated Hz
3. AMPLITUDE MODULATION (AM)
It is a form of modulation used for radio transmission
It has the two way radio communication applications
The basic concept is quite straight forward
The AM signal is changed in line with the instantaneous
intensity of the sound.
Signal carries the sound or modulation.
So that Radio frequency signal is the representation of the
sound wave
5. ADVANTAGES OF AM
It is simple to implement
It can be demodulated using a circuit consisting of very few
components
AM receivers are very cheap
No specialised components are needed
6. DISADVANTAGES OF AM
AM is a very basic form of modulation
Simplicity is one of its major disadvantage
It is not efficient in terms of its power usage
It is not efficient in terms of the its use of bandwidth
It is prone to high levels of noise
8. ADVANTAGES OF FM
It is resilience to signal level variations
The signals does not fall to a level where the receiver cannot
cope.
FM is ideal for mobile radio communication
FM is used for high quality broadcast transmissions
FM is widely used in many areas of radio technology including
broadcasting
Specially in two way radio communication.
10. DIGITAL AUDIO BROADCAST
DAB-is also known as digital radio and high definition radio
Analog audio is converted into a digital signal
Transmitted the signals on assign channel in the AM or FM
DAB offers FM quality audio on the AM broadband
In 1995, DAB technology was first developed UK
It became common in entire Europe
DAB is has better sound quality and new radio system
DAB receivers includes a small display
That provides information about the audio and visual
