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Graupner users get in here

Discussion in 'Cinestar Misc' started by Dave King, Jul 29, 2014.

  1. Dave King

    Dave King Well-Known Member

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    Hello All

    Lately I have had to do several jobs that involve taking my copter up close to our legal 400 feet limit. I've noticed that a few times in both my X8 and flat 8 copters I start to loose telemetry around 350 feet. It seems to vary between 350-400 feet. The radio will start beeping and my onscreen telemetry goes away. The copter never goes into fail safe, and I never lose control of the copter but I find it interesting that the telemetry goes out before the control signal. What's odd is that I can go out 300 meters straight at about 50 meters high and not have any loss of telemetry it only seems to occur when I am going up high in altitude and close to the copter. Anyone else experience this?

    I am also planning on doing a shoot for my show reel this year that will involve both of my copters at the same time. I plan on having both copters having cameras onboard to film. One copter films the scene and the other copter films the 1st copter. My question to those that have done something similar to this, have you ever flew 2 copters with the Graupner radios at the same time, and have you used 3 Graupners at the same time. My first thought would be that I would need to do the little track that disables the telemetry to one of the copters just like I do for my gimbal normally? So it would look something like this

    Copter 1 - TX 1 - RX 1 - Has fullTelemetry
    Copter 2 - TX 2 - RX 2/RX 3 - RX 2 will be active, RX3 will be paired up with TX 2 but not on so that it shuts off the telemetry.
    Gimbal 1 - TX 3 - RX 4/RX 5 - RX4 wll be active, RX 5 will be paired up with TX 3 but not on so that it shuts off the telemetry.
     
  2. Steve Maller

    Steve Maller UAV Grief Counselor

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    I'm no radio expert, but if the Graupners are anything like the Spektrum radios (which I know a little too much about right now) the telemetry channel is a whole different radio handshake, and may be deliberately lower priority for the radio. Remember, your transmitter is a transmitter, and its ability to be a receiver is orthogonal to that capability. One thing to consider based on what you're describing is how you have your antenna on the mx20 pointed. I usually use mine bent 90° to the right or 90° upwards. If you use yours upwards, it's got a lower profile for the radio when the copter's directly overhead. In that situation you may want to extend it straight towards the horizon. One more thing...do you have the radio log enabled in the mx20? Those logs will have a wealth of information. Too much for my little brain. :confused:
    Don't overthink it. As long as the radios are bound properly, the can coexist just fine, I believe.
     
  3. Dave King

    Dave King Well-Known Member

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    Thanks Steve I'll pointing the antenna straight out. AS for the multiple radios and receivers I know that there were issues where there were more than 1 telemetry signal being used at the same time as it was messing up the transmitters TX send signal. Andy Johnson Laird where are you when I need you? :confused:
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Imagine a circular disk with the tip of the Tx antenna stick through the middle of it (and therefore at 90 degrees to the long axis of the antenna). That disk represents the "side lobes" of the typical whip antenna such as you have on your Tx.

    If you point the long axis of the antenna straight up, then the side lobes extend out parallel to the ground all around you. If you point the antenna so that the long axis is parallel to ground, then the side lobes are at 90 degrees to the ground.

    Check http://www.antenna-theory.com/basics/radPatDefs.php

    So you point the antenna parallel to the ground and directly away from you, then the side lobes will be like a rainbow to your left and right and above you, but almost no energy extending away and up in front of you. That may not be what you want! ;)

    Andy.
     
  5. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Also, to amplify what Steve says, remember that the telemetry is coming back down from the copter using the copter's *receiver* as a transmitter -- with those piddly little wire antennae. Little wonder that you lose telemetry before you lose command and control -- the transmitter has a helical coil antenna that is much better as a transmitter.

    Andy.
     
  6. Steve Maller

    Steve Maller UAV Grief Counselor

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    Doesn't that explain why Dave's seeing marginal performance when the copter's directly above him? It's easy enough to adjust the antenna whilst in the air.
     
  7. Gary McCready

    Gary McCready Active Member

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    I originally had my Graupner Rx in between the two center plates, and I noticed when I would YAW I'd loose signal strength, when the Rx was on the opposite side from me. CF blocks the signal, so I have since moved it topside on both my MK birds. I did something like this, but made my own from recycled plastic. (Don't use CF) >
    http://www.quadrocopter.com/Quadrocopter-Receiver-Rabbit_p_1226.html
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    It's worth a quick experiment to confirm -- just don't hold on to the Tx antenna for too long as your body's capacitance will attenuate the signal and Bad Things might happen.

    Andy.
     

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