I want to start a project where I distribute many nRF24L01+ modules across the house. I am pretty sure someone has done that before. But before I wanted to begin I evaluated the modules using two Arduino UNOs and noticed two things:
Despite the possibility to select one of 126 RF channels. I get no reception on most of them.
First I thought that is because of interference with other WiFi and Bluetooth devices. So I performed a scan using the RF24/Scanner sketch. But it wasn't it.
I made a setup where I placed both transceivers on a table with 1m distance and played Ping-Pong. For each channel I sent out 1024 messages, counted the received messages on the other node as well the returned ACKs and ACK payloads.
The result was rather surprising. Less than a half of all the channels are reliable.
The sad thing is that those channels are also the most commonly used by WiFi networks.
That brought me to the second point. I thought the PCB antenna on the module might be not optimal for all frequencies but for one. So I made some research on PCB antennas. A PDF from Cypress on p. 13 suggests that the PCB antenna is emitting most of its energy to the right. But on my setup I had them facing away from each other.
I rerun the test with a different orientation of the modules. This time facing each other. I expected to get a wider range of channels that are usable this way. But it turned out the other way around.
So now I'm wondering if someone ever noticed the spectral sensitivity and directivity of nRF24L01+ modules and/or can point me to.
