What is free space path loss (FSPL)?

Free Space Path Loss (FSPL) is the loss in signal strength that occurs when electromagnetic waves travel through free space without any obstructions. It's calculated using the formula: FSPL(dB) = 20log10(d) + 20log10(f) + 20log10(4π/c), where d is distance and f is frequency. Simplified: FSPL(dB) ≈ 32.45 + 20log10(f_MHz) + 20log10(d_km). FSPL increases with both distance (6 dB per doubling of distance) and frequency (6 dB per doubling of frequency). This is why higher frequency signals have shorter range for the same transmit power.