The FSPL calculator allows you to determine the signal loss in free space between a transmitting antenna and a receiving antenna.
This tool is useful for RF engineers and technicians working on radio link planning and wireless system design.
Formula used
FSPL(dB) = 20 × log₁₀(d) + 20 × log₁₀(f) + 92.45 − GTx − GRx
Or :
d = distance between antennas (km or m)
f = signal frequency (GHz or MHz)
GTx = gain of the transmitting antenna (dB)
GRx = receiving antenna gain (dB)
FSPL = free space path loss (dB)
Explanation
The formula shows that signal loss increases with distance and frequency.
The gains of the transmitting and receiving antennas reduce the effective loss of the link.
The term 92.45 is a constant that adjusts the units for distances in km and frequencies in GHz.
Calculation example
For a link with:
Distance = 10 km , Frequency = 2.4 GHz , GTx = 5 dB , GRx = 5 dB :
FSPL = 20 × log₁₀(10) + 20 × log₁₀(2.4) + 92.45 − 5 − 5 ≈ 115.1 dB
Benefits and Use
- Allows you to estimate signal loss for radio or Wi-Fi links.
- Useful for wireless network planning and antenna sizing.
- Helps optimize range and signal quality taking into account antenna gains.
- Useful for comparing different distance and frequency configurations to minimize path loss.