Calculator Inputs
Formula Used
The log-distance path loss model expresses propagation loss as:
Where PL(d) is path loss at distance d, PL(d0) is reference loss at distance d0, and n is the path loss exponent.
For two measured points, the exponent is:
For received power prediction, the calculator uses:
How to Use This Calculator
- Select the calculation mode that matches your measurement data.
- Enter radio frequency, reference distance, and link-budget values.
- For two-point mode, provide two distances and two path loss readings.
- For reference mode, enter PL(d0) and one measured point.
- For regression mode, paste one distance,path_loss pair per line.
- Set an optional shadow fading allowance and design margin.
- Choose a target distance to predict future attenuation.
- Submit the form and review exponent, received power, graph, and exports.
Example Data Table
| Point | Distance (m) | Measured Path Loss (dB) | Comment |
|---|---|---|---|
| 1 | 3 | 48 | Near reference corridor reading |
| 2 | 5 | 54 | Low obstruction line of sight |
| 3 | 10 | 61 | Moderate indoor attenuation |
| 4 | 20 | 69 | Through partition walls |
| 5 | 30 | 74 | Mixed reflection zone |
| 6 | 50 | 81 | Longer indoor reach sample |
These rows can be pasted directly into regression mode using the distance,path_loss format.
Frequently Asked Questions
1. What does the path loss exponent represent?
It shows how quickly signal power decays as distance increases. Lower values suggest easier propagation, while higher values indicate stronger attenuation from walls, clutter, or reflections.
2. Why is free space often close to n = 2?
In free space, radio energy spreads predictably over distance without major obstructions. That geometric spreading behavior usually produces a path loss exponent near two.
3. When should I use regression mode?
Use regression mode during field surveys with several valid measurements. It smooths random noise better than a two-point estimate and gives a stronger overall fit.
4. What is a good reference distance d0?
A short, well-measured reference distance is best. Indoor studies often use one meter, while some outdoor tests may use longer anchors when measurement geometry requires it.
5. Why add shadow fading and confidence margin?
These allowances make predictions more conservative. They help account for uncertainty, movement, blockage, and temporary changes that real deployments often experience.
6. Can I estimate received power too?
Yes. The calculator combines transmitter power, antenna gains, system losses, and predicted path loss to estimate received power at the target distance.
7. What does R² mean in regression mode?
R² indicates how closely the fitted model follows your measurement pattern. Values nearer one suggest the log-distance model explains the data more consistently.
8. Why might my exponent look unrealistic?
Unrealistic values can result from poor calibration, mixed environments, short measurement spreads, antenna misalignment, interference, or entering received power instead of path loss.