Dual Graupner Rx's on ALTA?

Discussion in 'ALTA' started by Josh Lambeth, Sep 11, 2015.

  1. Josh Lambeth

    Josh Lambeth Well-Known Member

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    Hey Guys,
    Wondering if anyone has attempted to use 2 Groupner Rx's on the ALTA? I know on the MZ24 Tx and the MX20 you can bind 2 Rxs to the same radio. Just wondering if it would work. My guess is it won't since Futaba is S.Bus and Graupner is PPM and i'm not sure if the second RX location on the ALTA can accept a PPM signal.

    Anyway would love to hear your thoughts on this. Thank you in advance!

    Josh
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I was wondering the same thing, Josh.
    I've not seen any postings that suggest anyone's done it (yet!)

    Andy
     
  3. Josh Lambeth

    Josh Lambeth Well-Known Member

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    Guess I'll have to try!
     
  4. Tabb Firchau

    Tabb Firchau Administrator
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    Just the one input for Graupner

    2 for Spektrum and S.bus
     
  5. matt ragan

    matt ragan New Member

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    Josh,
    What did you find out, we just recieved our Alta today and I want to set up Gruapner as well
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    As Tabb says, there is only one place to plug in the PPM output from the Graupner Rx -- but perhaps a larger issue is that in the case of a lost link between Tx and Rx, as I understand it, the ALTA will execute a return to home, but will hover above home until a low battery reached triggers the autoland -- rather than an return to home and an immediate autoland.

    I'm not sure if there is a workaround for this.

    Andy.
     
  7. Michael McVay

    Michael McVay Active Member

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    I think there might be a way to do it - and you would still only use one input into the ALTA.

    I am doing this 100% from memory when I was reading a manual on either the MZ24 or the GR24 receiver so please look into it further if I point you in a direction that might help you.

    I recall reading that you are able to program both a SUM OUT signal (like most of us do with our Graupner receivers) and a SUM IN signal. The SUM in signal can accept a SUM OUT signal from a second receiver. So you would still bind both receivers to your transmitter and pass the signal from one of the receivers (not connected to ALTA) to the other receiver (the one that is connected to the ALTA). In theory it seems to make the second receiver the equivalent of a spectrum satellite type arrangement.

    The thing that is slightly different is that you would have to run a wire between them. I have not looked to see if the wiring channel on the ALTA goes all the way around - or if there is a clear channel to get from Receiver A to receiver B. There probably is - you would just need to remove the wiring channel covers and see. If so, you would be able to retain the clean look of the ALTA - if not, the wire would just need to be outside the frame.

    Reminder - this is from memory based on something I read a while back - my apologies if I am way off base on this.

    Good luck and please let me know if you look further into it and what you find out. Although I went Futaba for my Alta I have always had good performance with Graupner.

    UPDATE: Did a quick search and here are some small pieces of other posts in various forums:

    "1 receiver is set to SUMO and the other receiver is set to SUMI and then they are
    connected in ex code, the receiver set to SUMI take the output signal from the receiver
    set to SUMO and it is operated at the same time. The final channel of receiver
    is the output channel of SUMO, but you may change to the desired channel."

    "SUMI is Input, used for diversity"
     
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  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Excellent find, Michael.
    I wonder how we could implement the failsafe with Graupner? With Mikrokopter avionics it used a separate channel -- and if that channel's signal went away that constituted a lost Tx/Rx link.

    Andy.
     
  9. Michael McVay

    Michael McVay Active Member

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    Good question. I would imagine that Freefly must have this answer. I went Futaba for the Alta so I never had a reason to look into it - but a quick note to the support people would probably get to the bottom of it for everyone.
     
  10. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I shall dispatch a missive forthwith. :)
    Andy.
     
  11. Andreas Riem

    Andreas Riem Member

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    Why don't you use the GR-32? It's a dual receiver.
     
  12. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Can you even get the GR-32 any more? I can see the GR-32L -- but I seem to recall there was some disadvantage to the L-series radios? I know they're the lower cost line but I have a faint feeling that they lack certain features that the non-L series have.

    Andy.
     
  13. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I should have added that the GR-32, as Andreas points out, is a dual receiver, but they're packaged in the same enclosure -- so you really don't have as much spatial diversity as you'd get with two receivers on opposite sides of the carbon fiber "mass" of the ALTA.

    But certainly the GR-32 beats just having a single receiver.

    Andy.
     
  14. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I also found this at http://www.rcgroups.com/forums/showthread.php?t=2035316&page=8

    That is not about "US" receivers - the "L" versions have less functionality and are about half the price. If you compare the GR-12L to the GR-12 you will find it has no SUMO and SUMI and a lot more (or less). Just compare the manuals and you will see. If you don't need all the extras it's a good alternative.

    These L-versions seem to be tailored for the US market but are sold worldwide (AFAIK) but that is also true for the MZ series...
     
  15. Andreas Riem

    Andreas Riem Member

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    You'll get only the GR-32 ones in Europe, costs 139,99 Euro. I think it's good to face the four antennas without the original tubes towards ground and sky - therewith you can reduce the "mass" Problem in the middle.
     

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