EQPS Flashcards
Sound waves travel at what speed?
The speed of sound
Radio waves travel at what speed?
The speed of light
What allows radiowaves to travel so far without attenuating?
The are part of the electromagnetic spectrum and therefore do not require a medium to travel through
What does attenuation mean?
Weakening of waves
What is a wavelength?
Measurement of a wave from crest to crest
What is frequency?
Number of times a wave oscillates per second
If frequency and wavelength are inversely proportional, then a high frequency will mean?
Short wavelength.
What travels further, high frequency or low frequency?
Low frequency. The wavelengths are longer and therefore less susceptible to attenuation.
Outline the process of a basic radio transmission?
MICROPHONE detects small audio waves, OSCILLATOR creates a basic carrier wave. MODULATOR superimposes audio wave onto carrier wave. TRANSMITTER sends the radio signal. It is received by the receiving antenna, demodulated and amplified via the speaker.
What are the 4 methods of modulation?
Keying, Pulse modulation, Amplitude modulation, Frequency modulation.
In general civil ATC, HF, VHF and UHF are used for what purposes?
HF - Oceanic RT
VHF - RT between ATC and a/c
UHF - use on ground between ATC and vehicles
What are the emergency frequencies that are constantly monitored?
121.5 and 243.0 VHF.
Name 4 Navaids that use radiowaves in aviation?
VOR, DME, ILS, NDB
What is propagation?
The behaviour of radiowaves when they are transmitted from one point to another or in the atmosphere.
Name some methods of propagation experienced by radiowaves?
Reflection, refraction, diffraction, attenuation, absorption.
State the difference between skywaves and groundwaves?
skywaves are refracted by Ionosphere and redirected back to Earth’s surface, whereas groundwaves follow a parallel path to Earth’s surface.
What is the purpose of a repeater station?
As ground waves travel in a ‘line of sight’ path, repeater stations can help to increase range.
State the Ionospheres effect on skywaves?
During the day, the ionosphere is excited by the suns radiation, leading to increased absorption of skywaves. At night the ionosphere contracts leading to increased reflection.
HF & NDB signals suffer from some forms of interference. Name them?
Static interference, station interference, night effect.
Explain antenna shadowing.
As the aircraft turns, some parts of the airframe block the antenna. less apparent in modern planes that have multiple antenna.
What is a VDF?
VHF Direction Finder. Uses radio transmissions of an aircraft to determine the aircraft’s bearing from the station.
What is VCCS?
Voice Communications Control System. Connects various systems for ATC communications and merges them onto the same software/interface.
What is Selcal?
Sends 2 two-tone consecutive signals on a list of frequencies that chimes in the cockpit. Saves the pilot from having to listen continuously to noisy frequencies.
What is ACARS?
Aircraft Communications Addressing and Reporting System. Airline to aircraft communications. Broadly 3 types: ATC messages, Aeronautical operational control, airline administrative control.
What frequencies does civil aviation use?
118-137 Mhz VHF frequencies.
What is AMS?
Aeronautical Mobile Service. Dedicated frequencies communications system for emergencies and instances related to the safety and regularity of flights.
