What is the primary purpose of VHF/UHF communications in aviation and what modulation is most common?

What is the primary purpose of VHF/UHF communications in aviation and what modulation is most common?

• A. To enable voice communication with ATC and other aircraft; FM is the common modulation.
• B. To enable data transmission; QPSK is common.
• C. To broadcast weather radar signals; AM is used.
• D. To distribute cockpit music; FM is used.

Answer: (B)

The main idea is that VHF/UHF aviation radios exist primarily to carry voice communications between pilots and air traffic control (and between aircraft). For these voice channels, the most common modulation is frequency modulation (FM), specifically narrowband FM. FM gives good intelligibility of speech in the noisy aviation environment and with the varying signal levels you’ll encounter, and it supports robust reception with relatively simple equipment. While data transmission is available over some VHF/UHF links (and digital data modulations are used there), the primary purpose of these bands is voice, not data. Quadrature Phase Shift Keying is a digital modulation used for higher-speed data links in other contexts, not the standard for typical VHF/UHF aviation voice communications.

The main idea is that VHF/UHF aviation radios exist primarily to carry voice communications between pilots and air traffic control (and between aircraft). For these voice channels, the most common modulation is frequency modulation (FM), specifically narrowband FM. FM gives good intelligibility of speech in the noisy aviation environment and with the varying signal levels you’ll encounter, and it supports robust reception with relatively simple equipment. While data transmission is available over some VHF/UHF links (and digital data modulations are used there), the primary purpose of these bands is voice, not data. Quadrature Phase Shift Keying is a digital modulation used for higher-speed data links in other contexts, not the standard for typical VHF/UHF aviation voice communications.