Communication Systems Flashcards

HF radio communication in aviation is primarily used for which purpose?

Answer: Oceanic and long-range en-route communications

HF radio (2–30 MHz) uses ionospheric propagation to achieve communications over oceanic and polar routes beyond VHF line-of-sight range.

What type of modulation is used by HF aviation voice transceivers?

Answer: Single Sideband (SSB)

HF aviation radios use Single Sideband (SSB) modulation because it is more power-efficient and occupies less bandwidth than double-sideband AM.

What is the function of a SATCOM system on a commercial aircraft?

Answer: Enable satellite-based voice, data, and internet communication

Aircraft SATCOM systems use geostationary or low-earth-orbit satellites to provide global voice, data, and passenger internet connectivity.

Which connector type is most commonly used for VHF antenna connections in aircraft communication systems?

Answer: BNC or TNC (50Ω coaxial)

VHF antenna coaxial connections in aviation typically use BNC or TNC 50-ohm coaxial connectors, with BNC most common in general aviation.

What is a common symptom of a broken coaxial antenna feed line in a VHF COM system?

Answer: Very short transmission range and reduced receive sensitivity

A broken or high-VSWR coaxial feed line causes significant signal loss, resulting in greatly reduced transmit range and receive sensitivity.

What test instrument is used to verify antenna VSWR (Voltage Standing Wave Ratio) in aircraft communications?

Answer: Wattmeter/SWR meter

A wattmeter or SWR meter measures forward and reflected RF power to calculate VSWR, confirming antenna system impedance matching.