tools / RF & SDR
LoRa Range and Link Budget Calculator
Set your TX power, antenna gains, cable losses, spreading factor and bandwidth, pick an environment, and this gives you the receiver sensitivity, the maximum path loss you can afford, and an honest range estimate. It leans on the LoRa work behind my GPS-dart concept, where link budget was the whole game.
Range across environments
Free space is a theoretical line-of-sight ceiling; real coverage is closer to the rural/suburban/urban figures.
How it works
Receiver sensitivity
Sensitivity (dBm) = -174 + 10·log10(BW) + NF + required SNR. Higher spreading factors tolerate a lower SNR (SF12 sits near -20 dB), so they hear weaker signals, at the cost of airtime and data rate.
Budget to range
Max path loss = TX power + gains minus losses minus sensitivity minus fade margin. Free space inverts the FSPL equation for a theoretical ceiling; the rural, suburban and urban options use a log-distance model with a higher path-loss exponent, which is why the free-space figure is never what you actually get in a town.
FAQ
Is the free-space range realistic?
No. Free space is clear line of sight with no obstructions, the absolute best case. Pick rural, suburban or urban for something you can plan around.
Why does SF12 reach further than SF7?
A higher spreading factor copes with a worse signal-to-noise ratio, so the sensitivity floor drops and the budget grows. The trade is airtime: each SF12 packet takes far longer to send.
