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Xbee Pro 2SB XBP24-BZ7UIT-004 RSSI and range query

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I have three of these Xbee Pro modules with the UFL antenna connection.

I have used the Seeed studio UartSBee v5.0 to connect these via USB to computers.

I am using fairly generic 10cm long UFL to RPSMA pigtail cables to connect the Xbee modules to 5 dBi 2.4 GHz omnidirectional antennas.The pigtails have the sort of cable thickness you would see in a UFL cable inside a laptop.

I have set one module to be the coordinator and the other two to be routers.

When testing using a range test in X-CTU from the coordinator to either of the routers, the best RSSI I get is -76 dBM when the modules are 30 cm apart. When 4m away but still direct line of sight, I get around -91 dBM, i.e. only 1 bar of signal on the graph. This seems very low to me.

I am unable to get a router to associate to the coordinator through a single breeze block wall. This is a distance of 3m + wall!

I have fiddled with the power level settings on all of the modules. I thought maybe the signal strength was too high and I was saturating them but reducing power does not change things.

I have also turned off all my wifi routers and disabled the wifi adapters on the computers while doing the tests - no change.

I was expecting a lot more range out of the modules to be honest, especially as they are the pro version. I am only able to use them within the same room at the moment!

I think the seeed studio UartsBee USB interface is capable of providing more than enough current at 3.3V to drive them.

I would like to be able to communicate though at least one concrete wall as I aim to use these to monitor electricity meters situated in the core of our high rise office building. I would like to use omnidirectional antennas.

Any thoughts?

My only thought is the UFL to RPSMA cable might be cheap and degrading the signal. I bought it on taobao in china ;-) Can somebody recommend a robust UFL to RPSMA pigtail?

Would the 900/868 MHz versions be capable of easily penetrating a building core concrete wall + some?

link to Xbee module I have

link to UartSBee USB interface
asked Nov 17, 2014 in IEEE 802.15.4 by nangdec New to the Community (0 points)

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1 Answer

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Your issue is that you are trying to penetrate through a steel reenforced concrete wall. Something that RF just simply has issues doing. What you are going to most likely need to do is to place a router on either side of the wall. Then your modules can talk to the module on that side of the wall and through the wall via the two routers.
answered Nov 18, 2014 by mvut Veteran of the Digi Community (12,309 points)