1090 MHz Mode S “extended squitter” transponder

An Aircraft Transponder for the Experimental Aviation Community to meet the 2020 FAA ADS-B mandate.

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In 2020 all experimental aircraft will be required to update their transponders to meet the new ADS-B out requirement. Many of the commercial available options are very expensive so I thought I would give rolling my own a shot.

RF Front End

  • 250 Watt Peak Pulse Transmitter @ 1090 MHz
  • 1030 MHZ Receiver
    • Modulation PAM and DPSK
  • 1090 MHz Receiver
    • Modulation PPM
  • 978 MHz UAT Receiver 
    • Modulation FSK

Avionics Instrumentation 

  • WAAS GPS Source
  • Pressure Altitude 

Communication Buses

  • GDL90 (RS422)

Power Supplies

  • SWMPS 6v
  • SWMPS 50v
  • LDO 5v
  • LDO 3.3v


  • ATSAMC21E ---> Panel MCU
  • ATSAMC21G ---> Radio MCU


  • Monochrome OLED 1.54"

  • 1 × ATSAMC21E Arm MCU
  • 1 × ATSAMC21G Arm MCU

  • Assembled the first set of boards

    SN:10112410205/01/2018 at 19:27 0 comments

    Well, some errors where discovered in the first set of board, but I should still be able to use them for code development.

  • First Boards Arrive.

    SN:10112410204/16/2018 at 15:04 0 comments

    Got the boards back from fab, now just need to populate them. The two board cover all the digital logic, now just need the RF stuff, basically the hard part. A couple of careless mistakes on the large board but it should be fine, nothing to worry about at the moment. 

  • Avionics Board v0

    SN:10112410204/12/2018 at 16:40 0 comments

    Well I finished out the layout for the avionics board. Hopefully have it back from fab next week. 

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