I recently had my project exhibited at an exhibition in the middle of Trondheim city(in Norway(a country in the north)). It is Norways third larges city with 170 000 inhabitants. In my project I use Xbee series 1(1mW antennas), and when I was testing the system outside the city it worked very well and I could sent the signals over 30 meter wirelessly indoor. The night before the exhibition I was installing the project in the middle of Trondheim downtown, and as it turned out the communication between the two XBees did not work. Or - it worked, but the signal was dropping out all the time. The only solution was to place the receiver XBee one meter over the sender XBee. Even then If I put my hand between the two XBees the signal was dropping out.
There is a lot of signals in the middle of the city that may have interfered with the signals between the XBees, but one meter…and still does not work optimal…
I suspect it is a antenna problem. I use the XBee with the 1mW antenna, would it help to switch to the 50/60mW version, switch to series 2.5 or use another wirelessly transfer protocol?
It sounds like the problem is 2.4GHz noise. If you had access to a spectrum analyzer I’d suggest you start there and measure the noise floor, but spectrum analyzers are not something a lot of people have access to. Adding to the transmit power of the device would help get above the noise floor. As was suggested above you could also try changing device channels. You may find one with less interference.
The other idea I have only would be if the 2 devices antennas are not in the same orientation. Polarization issues could drop signal and increase noise enough that you loose signal.
Exactly which Series 1 XBees do you have (Which antenna option)?
Is the antenna clear of any other conductive objects?
I tried with the chip antenna and the wired antenna, but it made no difference. The antennas was clear of any other conductive objects to.
XBees are capable of using a number of different RF channels. You may be able to find a channel that has less interference from other 2.4GHz services. This paper may help: www.mobiusconsulting.com/papers/ZigBeea … erence.pdf
I havent tried this yet, but I will.
The other idea I have only would be if the 2 devices antennas are not in the same orientation. Polarization issues could drop signal and increase noise enough that you loose signal.
I tried to place the two devices in any possible way, but with no major difference. The only working position was to place the xbee just above the other.
So I will try to change the channel, but what about to go for the 50 or 60mW version, will that help? (Or change to series 2.5 <–what are the major difference between series 1 and 2.5?)
The non-PRO versions should yield over 100 ft. line of sight, or more.
Re Interference: WiFi should not be an issue; 802.15.4 simply transmits its packets in between 802.11 packets, in time. The form of interference that’s serious is an analog signal such as an analog camera or wireless speakers that are analog. These do not use the entire 2.4GHz band, so changing channels would correct the situation.
What antenna configuration do you have with the XBees? PC board chip antenna? U.FL connector with external antennas?
Series 2 XBees with ZigBee will make matters worse, as there are far more packets flowing to get the same amount of info passed, as in series 1.
If it’s not a poor connection of the antennas, let’s take a different diagnostic track here.