No it’s not difficult to reproduce. Take a “Bare” LoRa module and put a 50 Ohm (SMD) resistor directly over it’s antenna connector. Hook it up to a controller with a SD card, wrap it in plastic- and aluminum foil and then dump it with a battery in the tin-plated cookie jar to act as a kind of poor man’s Faraday cage. That, and patience , is all it takes. By using various carrier frequencies, different controllers at different clock-rates I made sure I was not seeing MMI.
At the chips default (Bw125 kHz, cr 4/5, sf 128) you get about 2 stray packets/hour. Varying bandwidth varies the occurrence rate and, no surprise, the reported RSSI. See the graphs below.
There is a bit of noise in the data, most likely due to the 24 hour sample period not being long enough yet.
Varying the other parameters and logging what’s happening is taking time and on-going. Preliminary result is that with increasing cr and sf the occurrence rate is dropping. And that makes sense.
The RadioHead library for RF95’s is affected. It’s easy to modify as per the write-up in http://www.loratracker.uk/?p=782. Since then I’ve not seen any stray decodes anymore which did not got flagged as bad. But testing is ongoing.
