Definition
Signal-to-Noise Ratio (SNR) on a radio link is the difference, expressed in decibels, between the received signal power and the noise floor at the receiver. A positive SNR means the signal is louder than the surrounding noise; a negative SNR means the signal is actually buried beneath it. Where the received-signal-strength reading tells you how loud a signal is in absolute terms, SNR tells you how cleanly it stands out from the electrical hash around it.
Why LoRa users watch SNR
For long-range, low-power mesh radio, SNR is often the deciding factor for whether a packet decodes. Typical LoRa SNR values run from about -20 dB to +10 dB. Remarkably, the spread-spectrum modulation LoRa uses can demodulate signals roughly 7.5 to 20 dB below the noise floor, a trait that lets a few milliwatts carry messages for kilometres. That capability is exactly why off-grid Bitcoiners reach for LoRa to relay transactions or coordinate without depending on carrier networks.
Reading SNR in the field
A higher spreading factor improves SNR tolerance at the cost of slower data and longer airtime, which interacts with regional transmit limits. When a hop is unreliable, compare SNR against signal strength: a strong signal with poor SNR points to local interference, while a weak signal with adequate SNR may simply need a higher spreading factor or a better antenna.
SNR and received strength are read together, not in isolation. See RSSI for absolute received power and Radio Duty Cycle for the airtime rules that govern how aggressively you can transmit.
In Simple Terms
Signal-to-Noise Ratio (SNR) on a radio link is the difference, expressed in decibels, between the received signal power and the noise floor at the receiver.…