Range Test - 2 Graupner Tx's to 2 GR-16's

Discussion in 'Electronics' started by Gary Haynes, Feb 17, 2013.

  1. Gary Haynes

    Gary Haynes Administrator
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    WARNING THIS WAS A GROUND TEST ONLY.
    FLIGHT TESTING MAY RESULT IN DIFFERENT BEHAVIOR.

    So since there has been so much discussion of using two Graupner Tx’s with one controlling the copter and the second one controlling the gimbal here’s a follow up test for that scenario. Here’s the results of an unscientific test.

    Equipment
    Graupner MC-32
    MX-16 Copter recv. Mounted on the Modi-Fly Recv Rabbit

    Graupner MX-20
    MX-16 Radian control mounted on the roll cross arm

    Iftron Mondo Extreme 1.5w tx. with a Bluebeam 3 lobe antenna mounted on boom 5 with the antenna pointing down
    Iftron Yellowjacket Diversity Receiver with dual antenna, Bluebeam 4 lobe and 4 lobe FAN antenna.

    Test location
    Back deck of my house at an altitude of 5,120 feet. Copter was setting on the top of a steel mesh patio table. Boom 1 was pointing south. (Note: typically this type of setup would produce a ground plane for the antenna’s which would affect signal strength. This is not the same setup as yesterday’s test due to 25mph winds)

    Test Site.JPG

    I planned on two test locations which can be seen on the Google Map View

    1. Cul-de-sac at 920 feet – Below Height of Test Pad by 49 feet
    2. Far point – 8,271 feet – Higher by 164 feet

    All points were line of sight.

    Test 2.jpg

    Results –

    I had good signal for both the Graupner's and the Video. At the furthest point I had two signal bars on the Graupner. If I stepped behind my truck I lost the signal. Also the signal was best with the antenna in a vertical position. When in horizontal position I lost 1 bar.

    I had complete control of the copter. I was able to do camera switching between the FPV and NEX7, trigger the NEX7 and do an MK calibration with the MC-32.

    There were no issues with control of the copter (camera switching) or any issues with control of the camera with the MX-20.

    930 feet - MC-32 top and MX-20 bottom - receiver data
    MC32 930 Ft.JPG

    MX-20 930 ft.JPG

    8,271 feet - MC-32 top and MX-20 bottom - receiver data

    MC32 8,271 ft.JPG

    MX20 8,271 ft.JPG

    Note: RX Strength on the MC-32 was a bit low at 15% but I think I was to close to my vehicle. As i walked around it was generally in the high 20% range.

    Lessons learned

    While I doubt that I will ever fly out to 1.57 miles it is reassuring to know that the setup is capable of doing that type of range. Graupner claims 4000m range with the Hott system. I was at 2,521m but ran out of places where I could test that distance and still be line of sight to the copter.

    I would suspect that with motors running while in flight the range may be different with all of the other electrical equipment running.

    Final Notes
    This setup was with an MC-32 for the copter and an MX-20 for the gimbal operation. I have no way of knowing whether other combinations of transmitters will give the same results. As noted ​
    WARNING THIS WAS A GROUND TEST ONLY.
    FLIGHT TESTING MAY RESULT IN DIFFERENT BEHAVIOR.
    IT IS IN NO WAY A RECOMMENDATION ON HOW YOU
    SETUP YOUR COPTER.
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Gary:
    What would you estimate the distance between the two receivers was?
    Also, were the antennae essentially parallel (sticking up), or was the one on the Modi-Fly doing its rabbit ears thing and the one on the gimbal crossbar lying sideways?

    If I read what you wrote correctly, there was no issue with having two RX bound to two different TX and both RX providing telemetry.

    Andy.
     
  3. Gary Haynes

    Gary Haynes Administrator
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    Andy bit hard to see in the photo of the rig but the MC-32 was talking to the GR-16 up on the Modi-Fly mast. The MX-20 was connected to the second GR-16 and looks like this, essentially a drooping angle but at about 90 degree separation. I just let them flop around.

    Distance between the two is about 15 inches.

    GR-16.JPG

    Modifly.JPG

    As to the telemetry the MC-32 was putting out both the MK info as well as the basic GR-16 stuff as shown in the photos. The MX-20 obviously only had the GR-16 data. I saw no difference in how everything seemed to working between the dual TX setup with individual receivers and a single TX driving 2 receivers together.

    Of course that doesn't mean that different TX types and different GR types wouldn't have an issue but in this specific setup it looked fine.
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Thanks, Gary. It would appear that some distance might be the magic.

    The downside of the horizontal antenna on the gimbal is that side-lobes are pointing up at the sky and down at the ground....

    But, more to the point, it looks like you've established a ground truth for which thanks!

    Andy.
     
  5. Bo Tornvig

    Bo Tornvig Member

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    Hi,

    Maybe a bit late, but please have a look at this:


    So it's only a matter of distance between the receivers - not the telemetry..?

    Cheers
    Bo
     

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