Free Space Path Loss (FSPL)
Calculate the free space path loss (FSPL), L = 20·log₁₀(d) + 20·log₁₀(f) + 32.44, from the distance d (km) and the frequency f (MHz). The result, in dB, is the attenuation a radio signal suffers simply by spreading through space, with no obstacles — proportional to the square of distance and frequency. It is the central term of any link budget: the greater the distance or frequency, the higher the loss and thus the more power or antenna gain needed. The 32.44 constant applies for km and MHz. Enter the distance and the frequency.
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Free space path loss (FSPL)
When a radio wave propagates in free space (no obstacles, reflections or absorption), its power thins out as it spreads over an ever larger spherical surface — power density falls with the square of the distance. Free space path loss (FSPL) quantifies that attenuation: L = 20·log₁₀(d) + 20·log₁₀(f) + 32.44, with distance d in km, frequency f in MHz and the result in dB. Note that the loss grows with distance and with frequency alike — higher frequency signals (millimetre wave 5G, or Ka band satellite links) suffer far greater loss and demand more directive antennas. FSPL is the dominant term in the link budget: start from the radiated power (EIRP), subtract the FSPL and the remaining losses, add the antenna gains, and check whether the arriving signal clears the receiver sensitivity with room to spare (fade margin). The constant 32.44 is the unit conversion factor for km and MHz (it would be 92.45 for km and GHz). Enter the distance and the frequency.
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