Model signal strength over distance using realistic reflections. See crossover effects with your antenna heights. Download outputs and share technical findings with your teammates.
These examples show typical values for planning. Your terrain and polarization can change results.
| Scenario | f (MHz) | d (m) | ht (m) | hr (m) | Pt (dBm) | Gt/Gr (dBi) | Loss | Notes |
|---|---|---|---|---|---|---|---|---|
| Wi‑Fi outdoor link | 2400 | 1000 | 30 | 2 | 20 | 2.15 / 2.15 | 1 | Compare selected model vs free-space. |
| LoRa gateway planning | 915 | 5000 | 25 | 1.5 | 14 | 3 / 0 | 1.2 | Longer range highlights d⁴ behavior. |
| Campus point‑to‑point | 5800 | 800 | 18 | 18 | 23 | 12 / 12 | 1.5 | Higher gains reduce required power. |
This calculator evaluates both free-space and two-ray received power, then selects a model based on crossover distance.
Notes: This is a simplified engineering model. Ground permittivity, antenna patterns, and polarization can shift real-world behavior.
Outdoor links near the ground often show a strong reflected component that combines with the direct path. A two-ray calculator helps you estimate received power when free-space alone looks too optimistic. By entering frequency, distance, antenna gains, heights, and practical losses, you obtain comparable values for free-space and two-ray behavior in one workflow.
The crossover distance dc = (4πht hr)/λ marks where the simplified two-ray trend typically dominates. Below dc, power commonly decays close to 1/d², or about 20 dB per decade. Beyond dc, the far-region approximation trends toward 1/d⁴, or about 40 dB per decade, amplifying distance uncertainty.
Antenna height is a high-leverage design variable because the far-region received power scales with (ht·hr)². Doubling one height can improve received power by roughly 6 dB, while doubling both can improve it by about 12 dB, assuming other parameters stay constant. This is why modest mast adjustments can outperform transmit-power increases.
Wavelength λ = c/f ties frequency to geometry. Higher frequency reduces wavelength and usually increases dc, extending the distance range where free-space behavior may be reasonable. Yet higher frequency systems can experience tighter alignment needs, higher feeder loss, and more sensitivity to obstructions, so the loss input remains important for realistic planning.
Antenna gains entered in dBi are converted to linear multipliers. System loss is applied as a linear divisor to represent cable attenuation, connector loss, mismatch, or built-in margin. Convert dB loss to linear with L = 10^(dB/10); for example, 1 dB ≈ 1.26, 3 dB ≈ 2.0, and 6 dB ≈ 4.0.
Use the result panel to compare the selected model with both component curves. If you enable free-space below crossover, the calculator switches automatically while still reporting both estimates. The Plotly chart visualizes how received power changes around dc, and CSV/PDF exports support documentation, peer review, and repeatable network design. For sensitivity checks, vary distance by ±10% and observe the dB change. Many planners reserve 10–20 dB fade margin for terrain and polarization effects. When the two-ray value is close to receiver sensitivity, increasing height is often the cleanest improvement.
It is the distance where the link typically transitions from free-space behavior to two-ray d⁴ decay, based on antenna heights and wavelength.
Beyond crossover, interference and geometry cause received power to scale approximately with 1/d⁴, unlike free-space 1/d² behavior.
Often yes for planning, but real links can deviate. Keeping both values visible helps you bracket performance in changing environments.
Gains multiply received power linearly. In dB terms, adding +6 dB total gain increases received power by 6 dB, all else equal.
Use 1 if you ignore losses. Otherwise convert known dB losses to linear, for example 3 dB ≈ 2.0, 1 dB ≈ 1.26.
No. It models one direct path and one ground-reflected path. For dense multipath or clutter, consider empirical models or site surveys.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.