What Is the Free-Space Path Loss & Friis RF Link Budget Calculator?
The Friis transmission equation calculates the received power of a wireless communications link assuming clear, obstacle-free line-of-sight propagation.
How Does the Free-Space Path Loss & Friis RF Link Budget Calculator Work?
Free Space Path Loss (FSPL) accounts for the geometric inverse-square spreading of radio waves. Summing gains and subtracting losses yields net received power P_rx in dBm.
Free-Space Path Loss & Friis RF Link Budget Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Free Space Path Loss calculates geometric attenuation of radio waves. Net received power sums transmitter power and antenna gains minus losses.
How to Use the Free-Space Path Loss & Friis RF Link Budget Calculator
- Enter carrier frequency in MHz and link span in km.
- Specify transmitter output power in dBm.
- Input antenna gains in dBi and system cable losses.
Step-by-Step Example Calculation
1 km Outdoor 2.4 GHz Wi-Fi Link
Input Values:
Understanding Your Result
FSPL (dB): Geometric path attenuation.
Received Power (dBm): Signal power delivered to receiver input.
Fade Margin: Safety buffer above typical -90 dBm receiver sensitivity floor.
Factors That Affect the Result
- Path loss increases by 6 dB for every doubling of distance or frequency.
When Should You Use This Calculator?
- Planning point-to-point microwave links, LoRa IoT deployments, satellite ground stations, and outdoor Wi-Fi bridges.
Assumptions & Limitations
- Assumes unobstructed line of sight (clear first Fresnel zone) without ground reflections or foliage absorption.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard IEEE telecommunications link budget formulation.