Free Space Path Loss Calculator
Calculate signal attenuation for radio frequency transmissions in free space
Calculate Free Space Path Loss
Direct line-of-sight distance between transmitter and receiver
Carrier frequency of the transmitted signal
Antenna gain relative to isotropic antenna (0 dB for isotropic)
Antenna gain relative to isotropic antenna (0 dB for isotropic)
Path Loss Results
Formula used: FSPL(dB) = 20log₁₀(d) + 20log₁₀(f) + 20log₁₀(4π/c) - Gt - Gr
Input values: Distance: 0.00m, Frequency: 0.000GHz
Applications: Satellite communications, cellular networks, WiFi, radar systems
Signal Analysis
Example Calculation
Satellite Communication
Distance: 35,863 km (geostationary orbit)
Frequency: 4 GHz (C-band)
Transmitter gain: 44 dB (satellite antenna)
Receiver gain: 48 dB (ground station)
Calculation
FSPL = 20log₁₀(35,863,000) + 20log₁₀(4×10⁹)
+ 20log₁₀(4π/3×10⁸) - 44 - 48
FSPL = 103.58 dB
Common RF Frequency Bands
Key Factors
Path loss increases with distance (inverse square law)
Higher frequencies experience greater path loss
Antenna gains reduce effective path loss
Assumes clear line-of-sight conditions
Understanding Free Space Path Loss
What is Free Space Path Loss?
Free Space Path Loss (FSPL) refers to the attenuation of radio frequency signals as they propagate through free space (vacuum) without any obstacles. The signal strength decreases due to the spreading of electromagnetic waves as they travel away from the transmitter.
Physical Principles
- •Energy spreads over increasing spherical surface area
- •Power density decreases with distance squared
- •No absorption or reflection in free space
- •Follows inverse square law physics
Friis Transmission Formula
PR = PT × GT × GR × (λ/4πd)²
- PR: Received power (watts)
- PT: Transmitted power (watts)
- GT, GR: Transmitter and receiver antenna gains
- λ: Wavelength (meters)
- d: Distance between antennas (meters)
dB Formula: FSPL(dB) = 20log₁₀(d) + 20log₁₀(f) + 32.45 - GT - GR
Applications and Limitations
Applications
- • Satellite communication link budgets
- • Cellular network planning
- • WiFi and wireless LAN design
- • Radar system calculations
- • Microwave communication links
- • Radio astronomy measurements
Limitations
- • Assumes perfect free space conditions
- • No atmospheric absorption considered
- • No obstacles or reflections included
- • Antenna pattern effects not accounted for
- • Polarization mismatch losses ignored
- • Real-world conditions add extra losses