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Transponders for Dummies.....me. Need explanation please.

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  • #16
    Originally posted by Uncle Willie View Post

    Transponders come in 4 basic flavors.

    Mode A ... Squawk and IDENT.
    Mode C ... Mode A Plus Altitude.
    Mode S ... Mode C Plus TCAS Collision Info, ICAO Code.
    Mode ES ... Mode S Plus ADS-B (Extended Squitter)

    Modes C, S, and ES all meet the requirements of Mode C.

    You can't buy a new Mode A Transponder anymore, so any Transponder will meet the Basic Mode C requirements for Class B airspace today.

    The ADS-B OUT function is an extension of the TCAS Collision avoidance system.
    To meet the minimum ADSB requirements you will need to transmit basic Mode C plus UAT ADS-B out Data ... Or Mode ES which incorporates the ADS-B Out Data.

    The Mode C or ES transmission is the beacon that allows other aircraft to see your location.
    You are not required to receive the ADS-B data but without it, you will be blind in seeing approaching traffic or weather.

    Mode C or better will allow Airliner TCAS systems to alert the pilots to your presence.

    Basic mode C will only inform a TCAS equipped aircraft that you are within a specified mile range.
    Your Altitude will be known but your direction will not. "Traffic 2 miles, 5700 ft."
    The distance is based on how strong a signal is received Air-to-Air, so it is not very accurate.
    2 miles could be anything between 1 and 4 miles.

    ADS-B will allow everyone to know what everyone else is doing in great detail.
    "Propeller Traffic, 11 o'Clock, 2 miles, SouthWestBound, Descend through 5700 ft. at 70 kts."
    Some additional info re the above: There are two possibilities for ADS-B "Out". It can be broadcast on either 978 MHz UAT (using TCAS) or 1090 MHz (ES) via a transponder. Mode ES just uses 1090 MHz. Ground stations pick up ES "Out" signals; these stations then rebroadcast the data for ADS-B "In" on aircraft so equipped. My understanding is that 1090 ES "Out" data does NOT go air-to-air, except to TCAS aircraft that have been modified to also process 1090 ES signals. So, two Mode ES equipped aircraft will NOT "see" each other unless they both have ADS-B "In" AND are close enough to a ground station to receive "In" data therefrom. Also, ground stations usually only broadcast the data for "In" when they are actually receiving "Out" data from aircraft in the area.

    Importantly, to meet the "Out" requirements for a GPS source, your GPS receiver must be permanently installed (i.e. not a portable), and also be WAAS enabled. That is, the satellite position information must augmented by WAAS ground reference stations (https://www8.garmin.com/aboutGPS/waas.html)

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    • #17
      "
      Hueychief

      Hueychief replied
      09-07-2018, 12:27 AM
      Transponders come in 4 basic flavors.

      You're so right, chief, I'm also a "master computer systems engineer", with specialties in 5 major programming languages, 5 operating systems and DBA on 4 major DBMS's , and I can throw a boatload of acronyms on you in a heartbeat. Yet I'm also experienced enough to know the importance of proper documentation practices on all this stuff. Hence my continuing efforts to improve the "Gremminger" terms and acronym file.
      Regards

      Frank

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      • #18
        Thank you all for these insights. I think I have a plan.
        "at 55 I did'nt GO over the hill, I FLEW over it"

        Sport Pilot Powered Parachute
        Sport Pilot Gyro

        Lifelong Member of the Dominator Fanclub.

        Currently building an Aviomania GS2 powered by a Honda 130 HP Engine. Expected completion about two weeks. Wait a minute....I finished it!

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        • #19
          So what's your plan? :)

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          • #20
            Probably Post #5
            "at 55 I did'nt GO over the hill, I FLEW over it"

            Sport Pilot Powered Parachute
            Sport Pilot Gyro

            Lifelong Member of the Dominator Fanclub.

            Currently building an Aviomania GS2 powered by a Honda 130 HP Engine. Expected completion about two weeks. Wait a minute....I finished it!

            Comment

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