I have been working with an Arduino Pro Mini 3.3V and a adafruit LoRa RFM9x module. I have it working and I have a question about RSSI strength and working distance range.
Indoors, a distance of about 25ft and transmitter is 1 floor (about 10ft) above the receiver. I am getting an SNR of 5-6, and a RSSI of -90ish dBm. I would expect with this short distance to get a much higher RSSI. When the receiver and transmitter are right next to each other I am getting a RSSI of -50ish dBm. My bandwidth and SF is default, TX power = 23 using the Radiohead Library.
I am just looking to see if this is expected transmission and RSSI readings at these distances?
Before I start looking into bad TX output stage on the LoRa module. I have a small spring antenna from Adafruit for 915MHz attached to both. I do have sma edge board connectors and SMA antennas for 915MHz 1/4wave on the way. I do have some other LoRa Modules to try that might work as well.
The only range tests that can be usefully interpreted are those done outdoors, with unobstructed line of sight. In general, RSSI values don't mean much, because they depend on so many factors.
For maximum range, it is extremely important to have an antenna that is a close impedance match to the TX/RX output and input, and is cut to the correct dimensions. Coils antennas generally do not meet those criteria.
The current range record for low power UHF LoRa transmissions is around 800 km, from a high altitude balloon.
Agree with @jremington, 'range tests' indoors are fairly meaningless, the absorbtion of RF of floors\walls in building varies to much for there to any meaningful comment on what RSSI\SNR should be expected.
Well, the bandwidth and SF settings do not affect the RSSI as such, and the Radiohead library does fantisise a bit about TX power, the RFM9x\SX127x devices are only capable of 20dBm, not 23dBm.