AET Communication Systems 3

Question 1

What is the purpose of SELCAL (Selective Calling System) in aviation communication?

Accepted Answer

To alert a specific aircraft when a ground station wants to communicate

Answer

SELCAL allows ground stations to alert a specific aircraft via a unique 4-tone code, enabling pilots to reduce cockpit audio monitoring on long-haul flights.

Question 2

Which modulation type is used by standard VHF aviation communication radios for voice transmissions?

Accepted Answer

AM (Amplitude Modulation)

Answer

Aviation VHF communication uses AM because it allows multiple signals to coexist on the same frequency and is compatible with legacy ground infrastructure.

Question 3

An aircraft HF radio is being checked and exhibits low output power but correct frequency. The MOST likely cause is:

Accepted Answer

Defective PA (power amplifier) stage

Answer

Low output power with correct frequency typically points to a failure in the PA stage, since frequency generation is handled separately by the synthesizer.

Question 4

What is the frequency range of the aviation VHF communication band?

Accepted Answer

118.0–136.975 MHz

Answer

Aviation VHF communication operates from 118.0 to 136.975 MHz, while 108–117.95 MHz is reserved for VOR/ILS navigation.

Question 5

A SATCOM system on an aircraft provides communication primarily via:

Accepted Answer

Geostationary or LEO satellites

Answer

SATCOM uses geostationary (e.g., Inmarsat) or low Earth orbit satellites to relay voice and data communications globally, including over oceans.

(AET) Aircraft Electronics Technician Practice Test

(AET) Aircraft Electronics Technician Practice Test

AET Communication Systems 3