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Friis Free-Space Path Loss (FSPL) RF Link Calculator

Free-space path loss accounts for the geometric expansion of electromagnetic spherical wavefronts traversing empty space.

Calculated Result
120.04 dB

Free-Space Path Loss (FSPL)

Attenuation Term 20·log10(d)

20.00 dB

Frequency Term 20·log10(f)

67.60 dB

Calculation Breakdown

  1. Apply Friis path loss formula in RF engineering unitsFSPL = 20·log10(10) + 20·log10(2400) + 32.44 = 120.04 dB

Path Loss vs Link Distance (dB)

Interactive visualization based on your current inputs

dB
0.034671011341 km5 km10 km20 km50 kmDistance (km)FSPL (dB)

What Is the Friis Free-Space Path Loss (FSPL) RF Link Calculator?

Free-space path loss accounts for the geometric expansion of electromagnetic spherical wavefronts traversing empty space.

How Does the Friis Free-Space Path Loss (FSPL) RF Link Calculator Work?

The calculation evaluates user-provided measurements using recognized domain equations, converts between measurement units, and adjusts for real-world efficiency factors.

Friis Free-Space Path Loss (FSPL) RF Link Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

\text{FSPL (dB)} = 20 \log_{10}(d) + 20 \log_{10}(f) + 32.44 \quad (d \text{ in km, } f \text{ in MHz})

Signal attenuation increases by 6 dB for each doubling of link distance or doubling of operating frequency.

How to Use the Friis Free-Space Path Loss (FSPL) RF Link Calculator

  1. Enter your primary measurements in the input fields above.
  2. Select your preferred units (e.g. metric or imperial) if applicable.
  3. Review or adjust operational assumptions such as field efficiency.
  4. Click Calculate to instantly generate the full results breakdown and visual chart.
  5. Use the Reset button at any time to clear the form and test a new scenario.

Step-by-Step Example Calculation

10 km 2.4 GHz Link

Input Values:

distanceKm:10
frequencyMhz:2400

Understanding Your Result

Your calculated result represents the realistic operational capacity or baseline output under the specified conditions. Comparing theoretical and effective outputs reveals the direct impact of turns, overlap, and practical downtime.

Factors That Affect the Result

Field terrain, operator experience, equipment maintenance, overlap margin, and weather conditions can significantly influence real-world output.

When Should You Use This Calculator?

Use this calculator whenever you need quick, verified estimates for job planning, budgeting, equipment sizing, or project timelines.

Assumptions & Limitations

  • Excludes atmospheric gas absorption, foliage attenuation, and multipath fading.

Frequently Asked Questions

Calculation Accuracy & Reference Note

This calculator implements verified, deterministic mathematical equations based on published standards. Results should be treated as professional engineering estimates; always verify critical operations with local equipment manuals and site inspections.

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