What is the maximum range of an Xbee? - Lets find out...

I have recently been pushing the limits of the XBee Pro to see how far it can go.
Unfortunately my current plane (SkyFun) only has a 38 minute duration and a maximum travel distance of 20km, this means the furtherst I have been able to go is 10Km (a 20Km return trip).
I have a 14dB patch antenna which has still shown signal of 85%+ out at this distance.

I wanted to find out how far the XBee could really go.
This meant planning a one way mission.

I spent about a week looking for the perfect start and destination, plotting the course and arranging access to the landing location with a local farmer.

The start point was my normal local park and the landing location was a farm paddock 16Km away.
The flight was over sparsely populated farm land and at a constant incline meaning I could increase altitude during the flight in order to get greater range.

My plan was to launch and monitor the flight from the launch location until I lost contact with the plane via Telemetry. After this I would drive to the landing location where the plane would be circling and manually land.

I calculated that even if I maintained contact with my plane during the flight and it made it all the way that I would still have time to make the 12 minute drive without running out of battery power.
With a tail wind, the plane would average 60Km/h at 45% throttle.

With everything planned and 45 test flights already in the bag with this airframe I was ready.

I launched and the plane took off to the waypoint as planned.
I was hoping for at least 12Km as this was ideal conditions.
The point on the map above shows the point I lost contact which is 10.6Km from the launch location.
The XBee maintained a very strong signal up until the last Km and then it began to drop off very rapidly.
It begins to be unusable below about 40%.

I packed up the ground station and drove to the destination which took just 11 minutes.
The plane was circling perfectly as expected and I put it in FBWA and landed without incident (apart from the slightly startled flock of sheep).

It turns out that the 10Km I had been flying to is around the maximum range of an XBee.

I am working on a much bigger aircraft that will have a 1 hour plus duration at a higher speed so I am going to have to look into more long range options for telemetry. GPRS / cell is preferable as we have excellent coverage here and fully routable and cheap internet plans. However, for experimentation I have been surprised at the distances that can be achieved with an XBee with a cheap patch antenna added on.

Here are a couple of tips for people wanting to achieve maximum range..

 - Minimize antenna cable length. My XBee is mounted on the back of my patch antenna and I run a long USB to my laptop. This maximizes gain and reduces lost signal.
 - I use either the ground or my car to enhance the ground plane effect. Putting the antenna in front of my car door or right beside my car makes a big difference to the distance. Also keeping it as close to the ground as possible.
 - Altitude is king, the higher you can fly the greater the achievable distance. Due to the fact my destination was on an incline, my end waypoint was 400m high relative to my starting point.
- Fly long straight missions so you can line up your antenna properly, I am building an antenna tracker that removes the need for this but Ardustation2 is currently broken since the last Mavlink updates.

Views: 41192

Comment by Colin Bouriquet on March 21, 2012 at 6:10pm

Toby> Where did you get your 900Mhz 14dBi patch ? Thanks.

Comment by Walter Clark on February 9, 2015 at 4:46pm

Toby,
I'm kind of blog illiterate so I don't even know if this is getting to you.  I spent weeks studying XBee in the Line Passing Mode. I bought two of the 2.4 GHz Pro Series One. I wired up a number of sensors and put one with an XBee in a small model airplane and damn it, I get useless ranges. No where near a mile. It wasn't mentioned in your article but I presume you were using the 900 MHz version. Is that right? Is it to be expected that the 2.4 PRO is still not good enough for air to ground where polarization angles can't be controlled?  I programmed both XBee's to maximum RF but the model plane has to be less than 400 feet to get an analog signal consistently through to the ground. I can go 600 feet with the polarization exactly right. I can get effective ranges if I use a 17 element Yagi but now it's a two man operation. Boy it's a good thing R/C controllers don't use XBee.  Any suggestions? Should I give up on the 2.4 Pro?

Comment by Toby Mills on February 9, 2015 at 4:55pm

I have never used the 2.4Ghz XBee, I suspect that is likely to yield poorer results due to more interference on that band.

However, with anything RF, power and gain are the two variables you have to play with in order to get distance.

Are you sure you have the pro versions?
What is the actual power output on those modules?

A 17 element yagi is probably overkill.

I used a 19db patch antenna which means it can be used without directionality up to about 1km but gives very long distances when pointed in the right direction. 

I suspect you won't get anywhere near these distances on 2.4Ghz, but you should get far greater ranges than you are finding.

As an update to this post I have now moved away from Xbee's and am now using the RFD900 radios which are absolutely brilliant. Far greater ranges are possible but I haven't done a max range check yet. I suspect I could get close to 20 to 30km with these.

 

Comment by Walter Clark on February 10, 2015 at 7:20am

Thanks for your reply Toby. Oh I am quite certain I have the Pro; they are $40 instead of $20. They are said to be 60 mW.

When you were using XBee, did you use any of the XBee sensor input ports, or were you going in through the DIN serial stream port?

Comment by Richard Sterling on August 24, 2015 at 12:42pm

Hey Toby, Where did you buy your RFD900 modems, in NZ or direct from RFDesign in Aus? 

Cheers,

RS

Comment by Ernesto L García Pinal on September 25, 2015 at 8:36am

Hello,

Can you tell me what antenna did you use. I'm looking for an antenna that maximize my range. Everyone says high gain LoS antenna but I can't find anyone online.

Appreciate any help.

Comment

You need to be a member of DIY Drones to add comments!

Join DIY Drones

© 2019   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service