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Thread: GPS Source for ADS-B Out

  1. #1
    Eddie Foy's Avatar
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    GPS Source for ADS-B Out

    I installed a Trig TT22 transponder last year. I need to add a GPS source to make it ADS-B capable. I am looking at the Trig TN72 but no tech info on it is available currently. I also want to add a 406 Elt with GPS. The TT22 uses an RS 232 serial bus to receive GPS info from the TN72.

    My question is this. Will the TN72 be able to provide GPS info to the TT21 and the ELT?

    Also, any other viable stand alone GPS sources to consider in the $500 price range.


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  2. #2
    fobjob's Avatar
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    I took this unit, which was recommended by Ack, for my 406 Ack install, took the 12v to 5v power supply apart, put it in a 'tube' of shrink tubing, wired the data cable directly to my Ack; it needed a 5.6k pull-up resistor to 5 volts....
    https://www.thegpsstore.com/Garmin-GPS-18x-serial-receiver-for-PC-P1842.aspx?gclid=Cj0KEQiA_eXEBRDP8fnIlJDXxsIBEiQAA GfyoeaaXc1JOQUBi64NQhR7ksDY3IjM3v_66TCsasTbNkUaAqn c8P8HAQ

  3. #3
    Bearhawk Builder's Avatar
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    Eddie, did you get an answer on this? Tying into the RS232 from the TN72 to feed the ELT? ACK E-04 to be exact.
    The ACK site says it will accept 'Bendix King , Garmin aviation formats as well as NEMA 0183 inputs'
    I can get it from the Ifly GPS but would rather connect directly to the TN72 if possible.

  4. #4
    wireweinie's Avatar
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    Just to be clear, the TN72 is not legal for certified ADS-B out stuff.

    You should be able to use the TN72 as a GPS source as long as any other stuff connected to it uses the same data programming, i.e., baud rate, Garmin or NMEA, etc. Also, if it is already connected to another unit, you'll need to connect the ELT in parallel with it. This means that the data out (transmit) line is connected to both the ELT and the other unit. This is usually ok but you'll need to run the setup and check for proper operation.

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  5. #5
    Bearhawk Builder's Avatar
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    Thanks Web, yes it's experimental. It seems the TN72 uses RS232 output and the ELT receives NEMA input so I take it that's not compatible. I'm guessing here. I can get NEMA at the correct baud rate from the I-Fly GPS if needed.

  6. #6
    wireweinie's Avatar
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    NMEA is a type of RS232 data.

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  7. #7
    Bearhawk Builder's Avatar
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    Am I right to say you really shouldn't split the RS232 signal from the GPS source? Rather, wiring them in series would require that the transponder has a signal IN port and would have to have a signal OUT port to go on to the ELT, correct? Or the GPS source must have two outputs. My understanding is these signals rely on timing of pulses and that splitting them between two receivers would upset that timing.

  8. #8
    wireweinie's Avatar
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    You can connect two units to one output but you need to do a functions check to make sure both units will operate correctly. The GPS's RS232 out/transmit line is connected to each units RS232 in/receive line. But this will only work if both receiving units can be programmed identically. This means both have to be set for Garmin or NMEA, same baud rate, etc. If the units cannot be programmed identically, then you'll need to use two separate GPS sources.

    Web
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  9. #9
    Bearhawk Builder's Avatar
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    Got ya, thanks

  10. #10

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    Doesn’t ADS-B require a WAAS GPS source? My exp Garmin system requires a supplemental WAAS source fo my ES transponder. In my case a GPS 20A. It appears the Trig equivalent is the TN70?

    Exp ADS-B transponders and WAAS GPS sources are one place exp equipment is significantly less expensive than certificated. Silly regulatory crap. I get that commercial operators might be held to a higher equipment standard but the average private airplane shouldn’t have to comply with the higher standard when the exp equipment works just as well.
    Last edited by stewartb; 10-25-2020 at 11:23 AM.

  11. #11
    Bearhawk Builder's Avatar
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    Yes, the TN70 is the WAAS source

  12. #12
    wireweinie's Avatar
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    I was under the impression you were using a TN72. If you have a TN70, you have two channels of RS232 data to work with. Make sure you read the details of the data found on each channel.

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  13. #13
    Bearhawk Builder's Avatar
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    No it’s a 72. Misspoke on the last post.
    TA70 antenna, TN72 GPS source, TT22 transponder.

  14. #14
    Steve Pierce's Avatar
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    TXPacer installed an inexpensive GPS puck on his ELT. Kept from having to run another wire all the way to the tail.
    Steve Pierce

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  15. #15
    txpacer's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    TXPacer installed an inexpensive GPS puck on his ELT. Kept from having to run another wire all the way to the tail.
    Same as what fobjob did in post 2
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