11.05.2 Communications Flashcards
What are the 3 communication groups?
- Aircraft communications
- Radio communications
- Accident investigation
What are AC communication systems?
- Interphone
- Passenger address
What are radio communication systems?
- VHF
- HF
- Satcom
- ACARS
What are accident investigation systems?
- Cockpit voice recorder
- Emergency locator transmitter
- FDR
What are 2 requirements of communication?
- Information (Audio signal)
- Carrier (RF signal)
What are frequency bands?
- HF - 3MHz to 30mHz (ADF and public radio stations)
- VHF - 30MHz to 300MHz (distance upto 200nm, VOR, ILS)
- UHF - 300MHz to 3GHz (military comms, DME, ATC and GPS)
How do you work out wavelength?
T = 1/f
Two types of wave propagation?
- Skywave
- Groundwave
Which frequencies use each type of wave propagation?
- High frequency - Skywave
- Low frequency - Groundwave
How if HF wave propagated?
Reflected by ionosphere
What affects HF reception quality?
Time of day and frequency selected
What are two types of modulation?
- Amplitude
- Frequency
What are audio system components?
- Microphones
- Speakers
What does microphone do?
Converts acoustic to electrical
What does a speaker do?
Converts electrical to acoustic
What are three types of microphone?
- Area
- Hand held
- Integrated
What are three types of speaker?
- Loudspeakers
- Small loudspeakers
- Cabin loudspeakers
What are radio system components?
Antenna, transmitter, receiver
What is a combined transmitter receiver called?
Transceiver
What are three transmitter components?
- Oscillator
- Modulator
- Power amp
What does an oscillator do?
Generates RF carrier frequency
What does a modulator do?
Couples audio signal to carrier in either FM or AM
What does a power amp do?
Generates power to TX
What is normal power output for a VHF system?
25 W