ADS-B in (Stratux) ADS-B out Garmin XPDR

Discussion in 'Avionics and Upgrades' started by labbadabba, Jan 31, 2017.

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  1. labbadabba

    labbadabba Pattern Altitude

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    So, question. A ship will only get TIS-B traffic if they have ADS-B out capability. But what if the in and out devices are separate?

    So, let's say I'm flying a club plane with the Garmin 345 XPDR with ADS-B out but I'm using a Stratux to drive my EFB. Will I get TIS-B traffic or do the devices somehow need to be tied into each other?
     
  2. GeorgeC

    GeorgeC Administrator Management Council Member

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    You will get traffic, the devices do not need to be connected.
     
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  3. labbadabba

    labbadabba Pattern Altitude

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    Stupid question. How do they know?

    i.e., They're not connected in anyway, there' s no interrogation that I know of between the devices. So, if were flying in formation where a plane next to me that had ADS-B "out" and I only had ADS-B "in", would I receive TIS-B traffic?
     
  4. GeorgeC

    GeorgeC Administrator Management Council Member

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    Yes, you'd be inside their "hockey puck".
     
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  5. exncsurfer

    exncsurfer Pattern Altitude

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    From my tiny knowledge of the system, the ads-b out triggers the ground stations to send data, then it can be received by whatever ads-b in device might be monitoring in range. The reason you aren't guaranteed traffic with only in is that you're not triggering the ground stations to send. disclaimer, i may have made this up.
     
  6. bnt83

    bnt83 Final Approach

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    A GTX345 will drive Foreflight...

    The GTX345 should also be configured for ADS-B in.

    There are settings in configuration pages that change the ADS-B out message, it can be set to 978 UAT (in) yes or no. I would think that would affect whether or not data will be uplinked but IDK for sure.
     
    Last edited: Jan 31, 2017
  7. labbadabba

    labbadabba Pattern Altitude

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    I'm not using FF. (yet) I currently use FltPlanGo and am playing with Aerovie. Both of which run off of the Stratux. (as opposed to the Stratus...)
     
  8. labbadabba

    labbadabba Pattern Altitude

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    Okay, these together make sense. Basically, the ADS-B Out sends a message and the ADS-B In gets the reply. The ADS-B ground station sends the TIS-B signal to an area of the sky where it expects the plane to be but only after receiving an interrogation.
     
  9. exncsurfer

    exncsurfer Pattern Altitude

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    Well, I would think the ground station just sends it out, no targeting involved, whoever is in range can receive it. thats the 'hockey puck' someone was referring to, the range of the broadcast
     
  10. exncsurfer

    exncsurfer Pattern Altitude

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    It seems silly to me that they would withold the broadcast of safety information in this way, are they trying to save power(on a ground station?) or just forcing participation? The data should be going out all the time in my opinion.
     
  11. labbadabba

    labbadabba Pattern Altitude

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    If that were the case, you wouldn't need the 'Out' solution.
     
  12. labbadabba

    labbadabba Pattern Altitude

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    On face value, I agree. I did stumble on an explanation that it's due to network limitations. They have a two-way interrogation in order to make targeted broadcasts to conserve network bandwidth.
     
  13. RotorDude

    RotorDude Pattern Altitude

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    Yes, but they don't limit their signal to "an area of the sky". AFAIK, they broadcast it isotropically (i.e. evenly spread to everyone within range) with the "puck" customized around the traffic that triggered the transmission.
     
  14. bnt83

    bnt83 Final Approach

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    Let us all know what you find out.
     
  15. ircphoenix

    ircphoenix En-Route

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    I heard that and I'm pretty sure it is nonsense. Or are they saying that their bandwidth is going to expand enough to cover everyone that has ADS-B out by 2020? I'm almost 100% sure that it is just to make sure everyone buys the transponders and can't skate with in only.
     
  16. George Mohr

    George Mohr Line Up and Wait

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    There's a lot of empty sky up there. Even when every airplane has ADS-B Out, the amount of airspace covered by "hockey pucks" at any moment will be a small fraction of the total volume of airspace. Without the ADS-B Out trigger for ADS-B In, they would need to basically spam coverage for the entire sky without knowing if there is anyone to listen. This, I believe, is the nature of the bandwidth limitation.
     
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