Communication Systems Flashcards
6 cards from real AET practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Communication Systems flashcards as text
What frequency band does aviation VHF communication primarily use?
Answer: 118–137 MHz
Aviation VHF communications operate in the 118.000–136.975 MHz frequency band for air-to-ground and air-to-air voice communications.
What modulation type is used by VHF aviation voice communication radios?
Answer: AM
VHF aviation communications use Amplitude Modulation (AM) because it allows simultaneous reception from multiple stations and simulates 'breaking squelch' when multiple transmitters key at once.
What is the channel spacing used by modern 8.33 kHz VHF aviation radios in Europe?
Answer: 8.33 kHz
Europe mandates 8.33 kHz channel spacing to increase frequency spectrum capacity in congested airspace.
Which component in a VHF comm transceiver ensures the carrier frequency is stable?
Answer: Frequency synthesizer with PLL
A frequency synthesizer using a Phase-Locked Loop (PLL) generates precise, stable carrier frequencies across all selectable channels.
What is the purpose of a squelch circuit in an aviation receiver?
Answer: Mute the receiver when no signal is present
The squelch circuit silences the audio output when received signal strength falls below a set threshold, eliminating background noise between transmissions.
What does SELCAL stand for in aircraft communication systems?
Answer: Selective Calling System
SELCAL (Selective Calling System) allows ground stations to alert a specific aircraft over HF/VHF without requiring continuous radio monitoring by the crew.