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How much space needs to be kept between several XBee PRO 868MHz without interference?

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Currently using the XBee PRO 868 MHz in the following configuration :

- 1 coordinator or control center (typically an XBee connected to a laptop through a USB adapter) + Yagi antenna.
- Around 10 end device modules on the field (small RPSMA Antenna sometimes with an RPSMA extension cable).

The distance between the coordinator and the end devices vary between 100 m and 2 km. The distance between the end devices antenna vary between 30 cm and 2 km.

All modules are configured with the default configuration + max power transmission.

The problem we're facing is that we can communicate between the control center and the end devices independently, we can also communicate when every module is activated except when the end device antennas are to close (30 cm). Is there any application notes or software that allows to check if a minimal distance should be respected? Is it possible that the modules are interfering with one another when too close?

Thank's for the support!
Adrien
asked Oct 30, 2014 in Multipoint Proprietary by Adrien Thyrland New to the Community (1 point)

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Adrien,

Do *not* run the unit at max power when antenna's are only seperated by 30cm. That can damage the radio. I would recommend you keep them 10 ft. apart and turn the power level down to minimum (PL=0 I think).
answered Oct 30, 2014 by kjensen8 Veteran of the Digi Community (623 points)
selected Nov 19, 2014 by Adrien Thyrland
Hi, thank's for the quick answer. I'm ok to reduce the power to the minimum but how can I then make sure that the end device will still be able to communicate with the control center 2 km away?

Is there any document that sum up the best practice with the XBee Pro 868 MHz?
There is only what is listed in the manual.  For the 2km range, you will most likely need to use PL 2  or 3. That is providing you have RF LOS conditions.
correct.  Turning PL=0 would only be done when testing in the lab.  When you deploy to the field you would then use max power (PL=4).  I don't think that's written anywhere else.
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