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Transponder replacementTransponder replacement

There’s no one-size-fits-all answer for ADS-B Out compliance. While a 1090ES Mode S transponder generally is going to cost more than most 978UAT Universal Access Transceiver ADS-B Out solutions, there are scenarios in which a 1090ES installation could cost you less.

Consider the following situations that might make transponder replacement a better choice for ADS-B Out compliance:

  • A working Mode C transponder is still required after the ADS-B Out rules take effect on January 1, 2020. If you have an older transponder, and especially if it has been reported as intermittent or is showing other less-than-stellar behavior, replacing it with a 1090 Extended Squitter product would give you both a reliable, digital transponder and ADS-B Out compliance—at a total cost that’s probably less than replacing a Mode C transponder and installing a separate ADS-B solution. If you’re shopping for ADS-B technology, talk with your radio shop or mechanic, and ask for installed quotes for both options.
  • Installation costs for a 1090ES transponder tend to be less than for a 978UAT, which could offset the UAT’s lower hardware cost. For example, a 1090ES installation frequently can re-use your existing transponder antenna and wiring, which can help to reduce installation costs. Keep in mind that you will need to install a WAAS GPS receiver and antenna if your aircraft is not already equipped with a complying position source.
  • 1090ES is an international standard and can be used outside the United States. Even if you do not fly internationally, if your aircraft is capable of doing so, this consideration could affect your resale value after January 1,2020.
  • 1090ES broadcasts directly to TCAS-equipped aircraft. Should there be any disruptions to an ADS-B ground station, your aircraft would remain visible to other traffic.
  • 1090ES ADS-B positions are visible on popular flight-tracking applications and websites, which can make the technology a good choice for flight schools, flying clubs, and other fleet operators.

To learn more about 1090ES transponder options, read “ADS-B: The Buzz About Transponders,” September 2015 AOPA Pilot, and “Avionics: Getting a twofer,” June 2015 AOPA Pilot.

For more information about available 1090ES transponders, see our listing of Mode S ADS-B Out solutions.