ATC Equipment Flashcards
What is the medium that sound waves travel through?
Air
What does “attenuate” mean?
Reduce the force, effect or value of. Thinning. Weakening .
Which travels faster sound waves or radio waves?
Radio waves - speed of light.
Sound - spend of sound.
E.g. Lightning vs thunder.
Describe 4 properties of radio waves:
- Do not require a medium to travel through.
- Can travel very long distances without being attenuated.
- Travel at the speed of light.
- May be reflected, refracted, attenuated, absorbed and diffracted.
- Part of the electromagnetic spectrum
Define wavelength:
Wavelength is the measurement from crest to crest.
Define amplitude in regards to waves:
Amplitude is the height of the waves.
Define frequency in regards to waves:
Frequency is the number of times the wave oscillates up and down per second. (Cycles per second, one cycle per second = one hertz)
In 4 steps, describe the working principles of a transmitting and receiving…
- Sound waves are converted to electrical signal.
- This is then superimposed on a radio frequency called a carrier wave.
- Carrier wave generated by the radio when the transmit button is pressed.
- Receiving radio removes the carrier wave and converts the electrical signal back into sound.
What are 4 components of a transmitter?
Microphone - converts sound waves to electrical signals.
Modulator - superimposes audio signal on a carrier wave.
Radio frequency oscillator - generates radio frequency carrier wave.
Transmitting Antenna - transmits radio wave
What are 5 components of a receiver?
Receiving Antenna.
Tuner - picks up transmitted radio frequency.
Demodulator- removes carrier wave.
Amplifier - boosts audio signal.
Speaker - converts audio signal to sound waves.
What would HF radio be used for in ATC?
Oceanic Flights (approx 3-30Mhz)
What would VHF be used for in ATC?
Radio Telephony between ATC and aircraft (118-137 MHz)
What would UHF be used for in ATC?
Radio Telephony on ground between ATC and vehicles.
What would AMS (Aeronautical Mobile Service) be used for in ATC?
A designated frequency for emergencies?
What is Radio Propagation?
Radio propagation is the behaviour of radio waves when they are transmitted, or propagated from one point on the earth to another or into various parts of the atmosphere.
What are the two principle types of propagation paths?
Ground waves - follow a straight line of sight. Travel directly from transmitter to receiver.
Sky waves - signal travels upwards into the sky, HF band and below are absorbed and refracted by the ionosphere. VHF band and higher will continue travelling into space.
What are the limitations of HF & NDB signals?
Static Interference - precipitation, thunderstorms.
Station Interference - Frequency congestion, care needed with selection & identification.
Night Effect - during the day the sun heats up the ionosphere and more is reflected?
Explain the effect of Antenna shadowing on RTF communications…
When an aircraft turns, the VHF Antenna may be shadowed by other parts of the airframe. This is less so nowadays as aircraft will have both top and bottom antennas.
Describe the use of Direction Finding (VDF)?
VDF Determines the aircraft bearing from a ground station.
They are capable of measuring the direction of arrival of radio transmissions from aircraft.
What other methods of communication are used in ATC other than radio?
Telephone - VCCS
Interphone/Intercom
Describe the VCCS…
Voice Communication &a Control System
Advantage - puts all the communications in one place / allows easy selection and deselecting of frequency.
Disadvantage- power failure means that back up separate phones must be available.
State the use of Selcal?
Selective Call - Means
