ADS-B Out

[Chappy Bishoff]

This is a total newb question, and I apologize as I'm learning, but is it the transponder that pushes the ADS-B Out data? Or is there more involved than this?

 

[GRG55]

This is a total newb question, and I apologize as I'm learning, but is it the transponder that pushes the ADS-B Out data? Or is there more involved than this?

The architecture for the entire ADS-B system is complex, involving equipment installed in aeroplanes plus ground stations across the country (including some on offshore oil production platforms to get coverage). The FAA didn't exactly follow all the conventions for international ADS-B in designing the US airspace system. Most of the world plans to use 1090 MHz only, which is the frequency existing Mode A, C and S transponders use.

The FAA is using two transmission modes, UAT and 1090ES. UAT is a two-way protocol at 978 MHz, and is the high bandwidth frequency for the FAA to send weather and traffic data to ADS-B In equipped airplanes. For transmitting ADS-B Out this frequency is limited by regulation for use only up to 18,000 ft. If you equip your airplane for ADS-B Out using UAT you will have a transmitter separate from your existing 1090 MHz transponder. And as the rest of the world slowly moves to ADS-B it is likely a UAT installation will only work in US airspace.

If you equip your airplane to ADS-B Out using 1090 MHz you will either be able to upgrade your transponder for ES (extended squitter) if it is Mode S or have to replace it if it is Mode A/C only and cannot be upgraded.

Because the FAA is using two frequencies, and airplanes equipped to receive only one cannot see airplanes transmitting on the other frequency, the US system has an expensive and complicated rebroadcast from ground station system.

Clear as mud?