Data telemetry range issues

We currently have a functioning ardupilot being used as a data telemetry unit. However, through field testing, we have found that the range we successfully achieve with the ardupilot and xbee data telemetry unit is approximately 0.3miles. This is a far cry from the 5 mile spec.

We purchased (3) ardupilots and the neccessary axilery equipment to completely make 3 units (Ardupilot, EM406, XBEE, Shield). However, again, we have field tested all of the compenents, and find the maximum range of any of the units to be 0.3miles, as stated above. Also, the other units are losing signal at or before approximately 0.1miles.

All field testing was done with line of sight and away from interference.

Could you please shed some light on why this range discrepency is taking place.

 

**NOTE: The Ardupilot is setup so it is only working as the middle man for data telemetry. There are no inputs or outputs; Just power, GPS, and Data telemetry

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Replies

  • hi john,

    We use X-stream Modem 900MHz with antenna.We get good commnication for telemertry.
  • Guys,

    I'm elated to say that we received our high gain antenna today and it fixed our range issues.
    We are now seeing over 0.5miles even in urban areas.

    Conclusion:
    My suggestion would be to fix the link on the homepage of this site to reflect the high gain antenna for new customers. Currently, you are linking them to the $7 antenna which does not perform to the ability of the $10 antenna. I think that almost everyone would want to spend the extra $3 to get a quality product.

    Thanks for the help,
    John
  • Conclusion:
    We tested the system with both antennas at 90 degree angles to the case. However, we were still only able to get a range of ~0.4 miles. Power going in is good and the antennas are optimized for 900 MHz. Only thing left is the actual hardware.

    Lastly, today we have been able to achieve a gps lock without shorting the pins. I'm unsure if this is usual and expected, but we have been shorting the pins until the blue light stops blinking every time before.

    We also have noticed that when we have the ground station up, even when the Xbee transmitter and receiver are right next to each other, that the "Error Out" interface of the GUI (Labview groundstation) will switch from the wanted green "Check" to the unwanted red "X". This error message tells us that at that instant the signal was lost, and we are no longer writing data to our file. Also, it displays that the voltage in is varying from 1V to 5V. This is not the case. I was able to verify that a steady stream of 5.1V is going into the Ardu, and a steady stream of anywhere from 3.6V to 3.8V into the Xbee transmitter.
  • That's right. XBee PRO 900's with wire antennas don't go very far. Users of the product recommend high gain antennas to get the rated range.
  • I see ^.^

    I'm just a bit picky you see; I also code websites.
  • Admin
    Like this ( test test)
  • Try putting that rat tail 90 deg to the Xbee board. It looks to me like its bent over parallel to the board. Might bee a ground plane thing? Easy to try. My 900 with a rat tail and a duck tested out to 1.2 mi. an the ground in my car. I goes further when out of the car. Tested with gps and Google Earth. Also could you have gotten a 2.4GHz duck? I have one for a video Rx that looks like and is the same length(externally) as the 900MHz. They extend the lead coax on the 2.4's. The only way i can tell them apart is the vid is SMA not RSMA like the Xbee.
  • Describe your RF setup a little bit more in depth.

    What antennas are you using, on both ends? How are they positioned on the aircraft and on the groundstation? What RF cables and connectors are involved?
  • Admin
    John,

    What Xbee module are you using: 900MHz or 2.4GHz? The 2.4GHz modules will be fairly directional while the 900MHz modules are less so. It might pay to use a diversity receiver system for the best reliability if that is possible with the Xbee modules.

    Regards,
    TCIII
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