1mw 802154 XBee - On Chip Antenna - Problem with indoor range

I have 1mw 802154 XBees with on chip (PCB) antenna. It is a unstructured mesh routing research project where the devices are expected to be smallest form factor low power and low cost so I want to be fair and not cheat with xbee pro or whip/dipole antenna.

The documentation seems to say indoors with whip or dipole antenna range is about 30m but less with PCB antenna. Clearly floors/walls will affect this, but in a regular house I have device desk height on ground floor and desk height immediately above on floor 1, distance about 3m, and they 'appear' to be out of range. Other similar positionings (eg same distance + wall) are out of range too.

This was unexpected. Assuming good conditions (no metal, interfetence etc) am I still expecting too much?

I have a Texas instruments sniffer (CC2531 USB Dongle) on floor 1 desk, it is very small and also with PCB antenna but it receives all the ground floor packets easily @ approx -69 rssi and floor 1 packets a few inches away @ approx -46 rssi (does -46 sound reasonable?). I have tried different devices instances and orientations, same issue. When I move them closer all is well.

I have power level default (level4 I.e. 1mw ?). Is there some other hardware/software configuration which be affecting this or may help? Can I 'add' say a whip antenna to the pcb without changing the actual module?

The XBees were sold together with and already connected to libelium waspmotes (arduino). The libelium advertising said outdoor range for 1mw on chip antenna (non-pro) 100m so I didn't anticipate 3m and between floors would be a problem. The advertising appears to be wrong though as the digi documentation says only 90m and says 90m is with whip or dipole and says it is significantly less with on chip antenna. With the 1mw on chip non-pro is range as low as this is to be expected? Perhaps I should just try to ensure sufficient density in the network, but if there are any useful configuration actions I can do (eg change channel (I am on 802154 ch11 which looks like its inside WiFi Channel 1, just looked at inssider app 4 aps on wifi ch1 !!)? multiple transmissions on broadcast packets? .etc..?) I would appreciate any configuration advice.

Given the circumstances of my project it may not be possible for me to change the modules plus may not be fair to the intention. Does any one have any advice

Assuming good conditions (no metal, interfetence etc) am I still expecting too much?

Yes. The chip antenna is pretty poor. The whip antenna is only about an inch long, and can be positioned parallel to the XBee, rather than perpendicular.

Lots of things cause interference. If there are electrical wires in the walls (an almost certainty), they will cause interference. Drywall screws or nails - oops, they’re metal. Flooring isn’t held down by gravity. Screws or nails, again.

and also with PCB antenna

I’m guessing that it is a much larger antenna plane, then.

Can I ‘add’ say a whip antenna to the pcb without changing the actual module?

I don’t think so. For the definitive answer, though, ask digi.com.

The libelium advertising said outdoor range for 1mw on chip antenna (non-pro) 100m

Pure, unadultered, bullshit. Even the whip antenna barely reaches that far.

Thank you for your response, I really appreciate it.

I guess I must have been naive or uneducated to believe the advertising.

Perhaps I can get them swapped for non-pro with whip or pro PCB.

I guess had the range "truly" been 100 metres then, while understanding there are different kinds of walls and ceilings I don't think 3 meters plus one average house wall or 3 meters plus one average house ceiling would be an unreasonable expectation (while understanding it is not guaranteed).

I didn't manage to find information about the whip antenna. All the images I see it is perpendicular to the board. You say it can run parallel, I wonder does it tilt or twist or something?

Thank you again.

I wonder does it tilt or twist or something?

It's just a flexible piece of wire. When shipped, the wire is pressed down flat against the XBee. Gentle manipulation is required to get the antenna into the desired configuration. Flat against the XBee works fine.

Hi PaulS, Thank you so much for your previous advice. I really appreciate it.

I have picked up a couple of what I understand are equivalent xbee modules to the ones I have with chip antenna but with wire/whip. The product code (XB24-A...-001 as referenced by the digi document) is identical except it has central letters "Wi" rather than "Ci". Hopefully some small range improvement.

I am using the identical program code and i had expected the module to behave identically given this and the same product code, but i am having some issues, the first of which is that the xbee does not appear to respond to the command to obtain the mac address parts. As far as i can see the existing libelium code sends an AT command but using API Frame mode then checks if any response is in the incoming buffer and reads off the response, but with the new module there appears to be no response, or at least the command appears to fail and the code returns an error.

Of course I need to look into this further, I am using libeliums API, but I am professional in C++ and I have the digi documentation, so if necessary I feel I will probably be able to make changes to the libelium api or could programme the module directly (though I would like to minimise necessary changes).

However what I really don't understand is what could possibly be different between the module with chip and the one with whip given the same product code. I am thinking baud rate? Which serial port I use? How long I should wait for startup? Or is it possible that the module that came with my libelium board may have come with some settings (such as the API mode etc) preset. Any thoughts or pointers on any of the likely causes would be very greatly appreciated.