Advanced LoRa Link Budget Calculator

Estimate LoRa received power, receiver sensitivity, fade margin, and range from first principles

animation
lora
lpwan
link-budget
path-loss
sensitivity
wireless
intermediate
Interactive LoRa link-budget workbench with scenario presets, path-loss animation, sensitivity calculations, spreading-factor comparison, and design-margin guidance
LoRa Link budget Path loss Sensitivity

Advanced LoRa link budget workbench

Move a packet across the radio path and see how transmit power, antennas, propagation loss, bandwidth, spreading factor, receiver sensitivity, and fade margin decide whether a LoRa link is usable.

-- dB Margin at selected distance
-- dBm Received signal power
-- dBm Calculated receiver sensitivity
-- km Range while keeping target fade margin
What Moves
The packet travels through transmit budget, path loss, receiver sensitivity, and margin decision stages.
What Changes
Distance, terrain, antennas, bandwidth, and spreading factor update both the visual path and the numeric budget.
Key Check
Received power must sit above receiver sensitivity, and practical designs keep extra fade margin above that threshold.
Model Limit
This is a planning model. Real sites still need regional compliance, noise checks, antenna surveys, and packet testing.

Rural water meter uplink

A modest sensor power level reaches a gateway several kilometers away because the path is open and the gateway antenna is elevated.

Target margin met
Animated LoRa link budget path A LoRa sensor sends a packet to a gateway while the visualization labels EIRP, path loss, receiver sensitivity, and fade margin. target range Sensor Gateway 1. EIRP -- dBm 2. Path loss -- dB 3. Sensitivity -- dBm 4. Margin -- dB 7.0 km at 915 MHz Rural/open path, n=2.6, obstruction 4 dB Target fade margin is met.
-- dBm EIRP after TX antenna and line loss
-- dB Path loss plus obstruction loss
-- dB Maximum path loss before raw sensitivity fails
-- ms Approximate airtime for a 12-byte payload

Margin meters

Path used
--%
Fade margin
-- dB
Airtime cost
-- ms

Formula trace

Transmit budget Start with conducted power, antenna gain, and line loss.
Propagation loss Distance, frequency, path exponent, and obstruction remove signal power.
Receiver threshold Sensitivity depends on thermal noise, bandwidth, noise figure, and SF SNR.
Design decision The link works only when margin stays above the target fade buffer.
SF Sensitivity Bit rate 12-byte airtime Target range Margin now Teaching takeaway

Sensitivity is calculated as -174 dBm/Hz + 10 log10(BW) + receiver noise figure + required SNR. Higher spreading factor lowers the required SNR, but it also increases airtime and channel occupancy.

Learning Support

Link Budget

Raw link budget is the largest path loss the link can tolerate before received power falls below receiver sensitivity. Fade margin is the extra buffer you choose to keep above that threshold.

Sensitivity

LoRa sensitivity improves when bandwidth is narrower, receiver noise figure is lower, or the spreading factor supports decoding at a lower SNR. It is not controlled by spreading factor alone.

Range Estimates

Path-loss exponent is the largest uncertainty in this simplified model. A small exponent change can move the range estimate by kilometers, so field measurements are not optional.

Quick Reference

Received Power

RX dBm = EIRP - path loss - obstruction loss + RX antenna gain - RX line loss.

Margin

Margin dB = received power - sensitivity. Design margin = margin - target fade margin.

SF Trade-off

Higher SF improves sensitivity and range, but lowers bit rate and increases airtime. That can reduce battery life and increase channel congestion.

Practice Prompts

1. Fix the Urban Link

Choose Urban basement, then recover at least 10 dB design margin without raising TX power. Which change helped most?

2. Compare SF7 and SF12

Hold the same distance and bandwidth, then move between SF7 and SF12. What improves, and what becomes more expensive?

3. Stress the Assumption

Increase the path-loss exponent by 0.5. Explain why a spreadsheet range estimate should not be treated as a deployment guarantee.
Technical Sources and Related Pages

Semtech LoRa Overview

LoRa and LoRaWAN technical overview explains the SF, range, bit-rate, and link-budget trade-off used in this teaching model.

Semtech Transceivers

SX1276 product information documents high receiver sensitivity and the wide LoRa operating frequency range.

Regional Parameters

LoRa Alliance RP002 is the right place to check channel plans and regional operating constraints.

General Link Budget Review FSPL, received power, fade margin, and antenna pattern basics. LoRaWAN ADR See how network feedback can reduce SF or transmit power when margin allows. LPWAN Range Compare LoRaWAN with other low-power wide-area technologies.