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I have two of these 24dBm XBee modules in a semi-LOS setup (1 receiver will be on the ground, obscurred by some tents/structures and other Burning Man camp crap), with these supposedly 3dBi antennas but I figure that will not get me far. Considering that one of my modules will be mounted 15ft up in the air on top of a bus, how can I maximize the communication distance?

Would either this or even better this antenna make a noticeable difference? Can I even attach my limited power 250mW XBee to such a large antenna and expect it to work?

Any other alternatives? I am even thinking of having a rotor setup with a directional antenna on a vehicle, but trying to avoid it at all costs...

Thank you!

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I recently used that same Xbee module in a project along with a pair of 6dBi omnidirectional antennas that while not identical look similar to the ones you've found and we got a range of 8 km line of sight but within an urban environment. It may have got further but geography limited how far away we could test and remain line of sight.

For that test one antenna was mounted out of the window of a house (not elevated above it) and the other one was mounted on a vehicle so roughly the same as your setup. A rough rule of thumb is that adding 6 dB of gain will double the range so you'd expect a pair of 6 dB antennas with a total gain of 12 db to have roughly double the range of the pair of 3 dB antennas with a total of 6 dB.

Using limited transmit power modules with large antennas does make sense although you can end up exceeding the legal radiated power limits for a band, however if you look at the end of the datasheet there's a list of FCC approved antennas and some exceed that amount of gain. But it's worth looking at that table anyway it might give you a few other antenna part numbers and styles to look at.

About the only other piece of advice I'd give is that for the best range it's worth keeping the antenna cable as short as possible, if you were to use a fairly average coax like RG-58 then 6 meters has about 3 dB of loss at that frequency so for example on the bus it'd be better to place the module right near the antenna and run back the data and power cables if possible.

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  • \$\begingroup\$ 8km in an urban environment? How did it remain LOS if the vehicle moved around? Yeah, I'm probably going to get that 6dBi antenna and stick with the 3dBi duck one for the non-vehicle one and have to test the range before I make it out to the desert. I specifically got a 1ft cable to minimize loss, good idea. I think that XBees do some sort of frequency hopping and is limited enough power to not hit any sort of FCC limits. Thank you! \$\endgroup\$
    – Glebbb
    Commented Aug 7, 2015 at 6:55
  • \$\begingroup\$ There were quite a few places it went out of contact along the way when it dropped out of LOS but the 8km was when the vehicle got back to an area that was a bit inclined compared to the house, but there were still local obstructions both ends so we were really impressed with the modules. The actual application only needed 2-3km in a rural environment so we ended up going with a 6dB at the base and 3dB for the remote sensors. Looking at where the Burning Man is held in Google Earth I think it should work really well over that sort of area. \$\endgroup\$
    – PeterJ
    Commented Aug 7, 2015 at 7:31

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