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ADS-B universal access transceiver frequency

Aviation Mechanic Airframe (AMA) practice question 5 of 26 on Communications, Light Signals, and Runway Lighting Systems. ACS element AM.II.I.K20 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONA general aviation aircraft is equipped with a universal access transceiver (UAT) for ADS-B. On what frequency does that transceiver broadcast?

  1. A978 MHz
  2. B1090 MHz
  3. C1575.42 MHz
Show the answer and explanation

Correct answer: A. 978 MHz

  • A — correct The broadband solution largely being introduced for general aviation ADS-B is at 978 MHz, accomplished with a 978 universal access transceiver.
  • B — incorrect 1090 MHz is the expanded use of the Mode-S transponder protocol known as 1090 ES, the other ADS-B data link.
  • C — incorrect 1575.42 MHz is the GPS L1 carrier frequency used in civilian aviation, which is a received navigation signal rather than an ADS-B broadcast.

BACKGROUND

ADS-B OUT combines the positioning information available from a GPS receiver with on-board flight status information such as location including altitude, velocity and time, then broadcasts that information to other ADS-B equipped aircraft and to ground stations. Two different frequencies carry these broadcasts with data link capability. The first is an expanded use of the 1090 MHz Mode-S transponder protocol known as 1090 ES. The second, largely introduced as a new broadband solution for general aviation implementation, is at 978 MHz using a universal access transceiver. An omni-directional antenna is required in addition to the GPS antenna and receiver.

STUDY TIP

Pair each ADS-B link with its user: 1090 ES rides the Mode-S transponder, while the 978 MHz UAT is the general aviation path.

KEY POINTS

  • ADS-B OUT broadcasts GPS position plus altitude, velocity and time.
  • 1090 ES uses the 1090 MHz Mode-S transponder protocol.
  • The universal access transceiver broadcasts on 978 MHz and needs an omni-directional antenna.

SOURCES

  • ama-airframe/ch11.txt "ADS-B"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.