Most people imagine Bluetooth beacons transmit equally in all directions. However, this isn’t usually true. The 2.4 GHz frequency that beacons use is easily blocked or affected (through electronic resonance) by items such as the casing, the battery and even the printed circuit board itself. Also, the design of the antenna, that’s usually etched onto the printed circuit board, causes the transmission to vary depending on the direction.
Printed Circuit Board (PCB) Antenna
The above 2D design leads to different radiation depending on whether you are viewing face on, sideways or end on. The following diagram from a very informative Cypress article (pdf) demonstrates how the radiation pattern can vary in the x y and z planes:
In practice, it’s best to perform tests to assess how the beacon radiation changes with beacon orientation. You can do this by measuring the change in RSSI as you orientate the beacon. You can measure the RSSI using an app such as nRF Connect.
For example, with the long 300m range iB003N-PA, we determined experimentally that the best range was when the non-battery face of the beacon was facing the observer.
iB003N-PA – Strongest signal for us was downwards in this photo
However, this was for our particular scenario. How and where the beacon is mounted can also affect transmission and hence range.
So, the next time you are testing the range or installing beacons, take some time to assess how the beacon orientation might be affecting the range.