EQT 1 Radio theory Flashcards
What is electricity
A form of energy produced by the movement of electrons in atoms. It can be used to transmit and receive electromagnetic energy.
What are radio waves
How fast do they travel?
Electromagnetic energy that are similar in behaviour to light waves.
Travels at 3000000000 metres per second
What is audio limited by?
Range
How loud someone speaks
Absorption by materials within range
Attenuation
What is one wave cycle
Each time wave travels from zero up down and back to zero this counts as one cycle
What is amplitude
The max displacement or value attained by the wave from its mean value during the cycle
Basically from zero to peak and back to zero
What is wavelength represented by?
Lambada
What is a wavelength
The distance in metres or part of a metre between corresponding points in consecutive waves.
What is the frequency
Cycle per second - hertz
What is 1m wavelength in MHz
300 MHz
How do you calculate velocity
Velocity = frequency x wavelength
If the wavelength is longe is the frequency higher or lower?
Lower
What are carrier waves produced by?
A local oscillator
Local oscillator can manipulate what?
Amplitude or Frequency
What does AM stand for
Amplitude modulation
What does FM stand for?
Frequency Modulation
What does a modulator do?
Combines the audio and carrier wave
What are the advantages or FM
Resilience to noise
Easy to apply modulation at low power - no boosting of amplitude required
Use of efficient RF amplifiers - less battery power required
Advantages of AM
Stronger stations can override weaker
A heterodyne (squeal) indicates a blockage
Is AM or FM used in ATC
AM
What is the ideal length of an antenna
The same as wavelength of the frequency transmitted
What does a RF amp do?
Makes signal stronger but also amplified static - has a noise gate fitted
