Going for distance on the 3dR Telemetry modules.


For the longest time I've only been able to get about 500 meters out with my stock 3dR telemetry modules. No matter what settings I tried I couldn't get any further. There's been discussions in the forum about the specs of the radio modems and how far you can go. I've even swapped out telemetry modems thinking I might have fried one. Finally I broke down and ordered some parts from Servo City and built an antenna tracker. Then utilized a 900mhz -8dbi patch antenna I was using for FPV before I switched to 5.8ghz. Today I finally made it out to 1.3km! This is with the patch antenna and a stock antenna onboard the plane. 

I had to reduce my telemetry speed clear down to 2400 baud before I could get a relatively solid signal back to the ground station. Anyone have any suggestions for 3dR telemetry radio settings? I'd love to make it out to 2 km on the 3dR modules and still have a solid telemetry link. I've been eye'ing the RDF900's for quite some time. As much as I'd love to throw more power at my signal I'd like to squeeze what I can out of what I have. 

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  • They are no good for long range.

    ECC uses inefficient 12-bit golay.

    Netid, length and checksum are not protected by ECC.

  • Andrew good advice. I'll keep an eye on that and so far according to the numbers it looks good. I have the GPS mounted out on one wing and the Frsky RX wires on the other wing. 

  • Developer

    Hi Darrell,

    I use this one a lot:


    It has PPM sum, and no telemetry.

    Cheers, Tridge

  • Developer

    Hi Scott,

    I'm glad it's working a bit better for you now.

    One thing to watch for with the FrSky telemetry is GPS interference. I used the FrSky telemetry modules last year, and found that GPS performance degraded a lot. It seemed that the FrSky telemetry transmissions in the plane are putting out some unwanted signal at 1.5GHz, which caused GPS dropouts. So watch your satellite count. I have stopped using the FrSky telemetry because of this.

    Note that APM uses GPS for more than just position - it also plays an important role in attitude estimation.

    Cheers, Tridge

  • Looking good now gang. I was able to get out to 1.3km from launch with copper shielding around the ground station's 3dR telemetry module. Looking at the noise floor on the RX I might actually switch it back to Tin. This flight was at a airspeed of 64 vs the 24 I had to do last time. The two bad spots in the downlink data is when the plane was making a turn and the antenna may have been shadowed. 

    I installed my Frsky radio with telemetry in the plane. The Frsky with a stock setup dipped about 1km from launch and Failsafed into Auto Mode so it'd complete the mission. There's still much to do but thanks for the help folks! This is why I love the DIY community! 


  • Well this is looking better. I just did a test run out at the field at 1.3mw of power. Held a solid signal out to 270 meters. Only thing is the laptop started to die and went into sleep mode half way through the run. I was able to revive it for a bit until the laptop battery died. I'll take the plane out for another run tomorrow. 



  • @Scott: Here in Norway i pay equal 40USD per month for a 6gb dataplan.

  • Bill - I'll get some pictures later today

    Andrew - I'll try a few of the other suggestions. I already have a USB dumb hub between the radio and the computer. Sadly the Surface only has one USB port. I'll pick up a few rings from the electronics store and clamp them on. I've been meaning to pick a few up anyways.

    Tommy - I'd love to do MiFi but the cellular companies here in the states like to rob people blind for data. Not to mention they charge a monthly rate for the device. 

    John - I'm flying fixed wing and have tried numerous spacing setups. Usually I'm at 400' AGL or 50' below depending on where I'm at. One of my fields the safety officer has a heart attack if a plane looks like it's above 400' AGL. My other field is a little less restrictive. I tend to keep it around 400' since DHS goes down that route in their helicopter every now and then. Plus there's paragliders and people jumping out of a perfectly good airplane for some reason. 

  • The cost is almost "nothing" and the area where i fly, i can go xxx km in each direction without loosing any 3g signal. Works great!! And it's so simple to configure and use :)

  • Developer
    @john: you a good point. Low level flying will have worse signal to noise ratio. Noise is the reflected wave coming from your own transmitter desensitizing the reciever.

    @tommy: 3G may give you a wider operating area, but the trade-off is cost, latency and only area covered by the network.
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