Free-space pathloss measures signal attenuation between two unobstructed antennas. Received Signal Strength Indicator (RSSI) shows resulting power at the receiver input. Understanding both values builds a reliable link-budget foundation. You reference them when designing point-to-point wireless links for telemetry or broadband. Both metrics ignore obstacles and atmospheric losses for simplified planning.
This calculator estimates pathloss and expected RSSI instantly. You adjust frequency, distance, antenna gains and cable losses, then review updated results. Interactive fields eliminate manual formula work and reduce errors. Real-time feedback accelerates feasibility checks during site surveys and hardware selection. Engineers save time analysing what-if scenarios before committing to field tests.
Apply the results to choose antennas, radio modules and safety margins. For example, discovering a −75 dBm RSSI confirms a 10 dB fade margin. You then decide whether higher-gain antennas are required. The calculator therefore strengthens project documentation and supports confident stakeholder discussions. Use exported figures when populating network design spreadsheets or installation guides.
Technical Details:
This section outlines key parameters and internal logic.
- Frequency field accepts MHz or GHz units.
- Distance accepts metres or kilometres for flexibility.
- Reactive formula updates results on every keystroke.
- Antenna gains and cable losses combine automatically.
- Additional loss box represents obstacles or fade margins.
- Outputs show FSPL and RSSI with two-decimal precision.
- URL parameters persist settings for repeat analysis.
| Formula | Purpose |
|---|---|
| FSPL = 20 log₁₀(d) + 20 log₁₀(f) + 32.44 | Compute free-space pathloss in dB |
| RSSI = Tx + Txgain − losses − FSPL | Estimate received power in dBm |
Calculations-and-Scoring:
Verify and interpret results using these subsections.
Formula Breakdown
FSPL grows logarithmically with distance and frequency. The constant 32.44 aligns units to km and MHz.
Worked Example
At 2.4 GHz across 1 km the FSPL equals 100.04 dB. A 20 dBm transmitter with zero gains delivers −80.04 dBm.
Interpretation
RSSI above receiver sensitivity ensures reliable decoding while maintaining a healthy fade margin.
Recommendations
Increase antenna gain or shorten distance when RSSI falls within 3 dB of sensitivity.
Step-by-Step Guide:
Follow these steps to obtain reliable figures.
- Enter transmitter power in dBm.
- Add transmitter antenna gain and cable loss.
- Select frequency unit, then type frequency value.
- Choose distance unit and enter separation.
- Input any additional path losses.
- Review FSPL and RSSI cards; adjust fields until targets are met.
FAQ:
Review common questions for quick clarification.
Why use MHz instead of GHz?
Smaller units give finer resolution when exploring narrow frequency steps.
Does the calculator handle non-line-of-sight paths?
No. The FSPL formula assumes clear air and ignores diffraction or reflection losses.
Can I model rain fade?
Include expected attenuation under “Additional loss” to approximate weather effects.
What if my result is positive RSSI?
Positive values indicate amplification or unrealistic parameters; re-check gains and losses.
How precise are the constants?
The 32.44 constant is derived from physical constants and is sufficient for engineering estimates.