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.
Comments
What altitude are you at ? Is this a plane or copter? The furthest distance Ive attempted with 3DR modems is just over a mile @400 ft AGL. Ths was with the stock omni antennas and a clear LOS.
I think it's much easier to just use a RN-174 and a small 3g hotspot. Not much weight and "unlimited" range
http://diydrones.com/profiles/blogs/skywalker-x8-video-and-telemetr...
@John start looking at SWR meters on Google and no end of ham radio how to's
On my X-8's we usually can go over 3km and mission planner still reports back 90% telemetry strength. That's about where my JR9503 on DSM2 tends to get a little spotty.
X8 wing has 3DR 900mhz radios with stock antenna on aircraft and ground. Ground radio is velcroed to the back of the laptop screen. When I mounted the ground antenna near out FPV rx antenna, range can be reduced to 500-1000metres. Video is lawmate 1.3ghz 1W tx with large omni antenna. The X8 is huge, so all 3 radios are mounted far apart.
oh, I also notice your last test was in a suburban environment. Getting good range close to houses like that is very hard - you only get really long range in nice open areas, with the antennas well off the ground.
The signal from these radios isn't like a laser - it spreads out and is affected by anything close to the path between the two radios.
Cheers, Tridge
Hi Scott,
ok, at least you now know your local noise is your limiting factor. A difference of 20 to 60 is huge - thats about 20dB. Each 6 dB doubles your range, so 20dB would be more than 8x the range, although part of the increased local noise could be the higher gain antenna (that would probably explain about 5dB of the extra noise).
There can be lots of reasons for local noise. One common one is noise from the computer transmitted over the cable (conducted noise). To see if it is conducted or radiated noise see if the noise level changes a lot as you move the antenna closer to or further from the computer, while keeping the antenna in the same orientation. If it doesn't change much then it is probably conducted noise.
If it is conducted noise then there are several things you can do:
It is amazing how much difference fiddling around can make. If you get things just right the 3DR radios can get 10km or so, although it's difficult to achieve, which is why I listed the expected range much lower than that. Too many people would be disappointed if the range figure quoted in the docs was that high, even though it is achievable if you put enough effort into reducing RF noise.
Cheers, Tridge
@Jack - You're right it is ironic that they don't crank up their own telemetry. I followed your blog on RCG for quite awhile and saw the fun you were having there. I can tell you that I'm allergic to Spektrum. I've watched a few of those folks get upset when their Telemetry dips out after 400'.
@Bill - I do have the correct antenna with the red dot on it. I know with RCT who knows what type of antenna they're giving you. I tossed them in the trash and bought proper antennas from the get go.
@Andrew - I took another look at my graphs per your suggestion and noticed my Local Noise was 60, yet my remote noise was in the 20's.
Seemed kinda odd so for shiggles I grabbed some Tin Foil out of the cupboard and decided to go on a walk. I set both my Telemetry units to the lowest setting "1" and aimed my 8dBi antenna down the trail. I made it about 50 meters down the trail before I noticed my remote noise flatline. I then wrapped the tin foil around the 3dR module and watched my signal come back to life. I continued down the trail to about the 100 meter mark....
After this little discovery I went back and plugged the laptop in to the 8dBi antenna and wrapped that module in tin foil. I then grabbed the drone and started walking down the trail. Again both radios set to the lowest power setting. This time instead of at an airspeed setting of 24 I brought it back up to 64. Here's the outcome of the little experiment....
Looks like I'm making it out to 100 meters on the lowest power setting and maintaining a good connection. I'd of taken it back out in the field but it was getting late. I should have some time tomorrow to give it a whirl and report back.
The fidgety modems are specifically for telemetry, while you're still presumably using a high end stock RC transmitter like the Spektrum for control, which doesn't require a wiki or an antenna tracker to get working. There's some irony in the stock RC radios using full duplex chips capable of telemetry but only being able to go 1 way because of a simple piece of software & all the trouble that necessitates.
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