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Calculators / Friis Transmission
Friis Transmission
Calculator
Calculate received signal power, free-space path loss, link margin, and maximum range for any RF communication system. Essential for link budget analysis — used in WiFi, 5G, satellite, radar, and any wireless link design.
Transmitter
Free-Space Path
Receiver
⚙ Friis Transmission Engine
Solving for: Received Power (Pr)
20 dBm = 100 mW
λ = — m
Free-space path loss = —
0 dBi = isotropic. Dipole = 2.15 dBi
0 dBi = isotropic antenna at receiver
Minimum detectable signal at receiver
Advanced / Loss Parameters
dB
Coax + connector loss at transmitter side
dB
Coax + connector loss at receiver side
Atmospheric loss over link distance
Loss due to TX/RX polarisation mismatch
dB
Antenna misalignment loss
dB
Receiver noise figure (typical LNA: 2–4 dB)
Calculated Results
Received Power (Pr)
—dBm
FSPL—
Link Margin—
Pr (Watts)—
Max Range—
EIRP (Pt + Gt − cable)—
Total Path Loss—
SNR at Receiver—
Thermal Noise Floor—
Free-space λ—
Link Status—
Enter values above to calculate.
📖 The Friis Equation
The Friis transmission equation, derived by Harald T. Friis in 1946, gives the power received by one antenna from another in free space.
Friis Equation (linear)
Pr = Pt · Gt · Gr · (λ/4πd)²
In dB (link budget form)
Pr = Pt + Gt + Gr − FSPL
FSPL = 20·log(d) + 20·log(f) + 20·log(4π/c)
FSPL Simplified
FSPL(dB) = 20log(d_km) + 20log(f_GHz) + 92.44
d in km, f in GHz. Classic telecom form.
The link margin is the excess received power above the receiver’s minimum sensitivity. Positive margin = reliable link. Engineers typically design for ≥10–20 dB margin for fading.
📊 Link Budget Visualiser
Live Budget
|
◉ Power vs Distance & Budget Breakdown
Chart Type
Freq sweep
2.40 GHz
0.1 GHz30 GHz
Gain sweep
0 dBi
−1040 dBi
Received Power vs Distance
ℹ
Link Budget Insights
Enter link parameters above to see real-time link quality analysis.
Common Applications
WiFi & Cellular
Indoor/outdoor coverage planning, cell radius calculation, and interference analysis for 4G/5G networks.
Satellite Links
Uplink/downlink budget for LEO, MEO, and GEO satellites. EIRP and G/T calculations for Earth stations.
Point-to-Point Microwave
Long-haul backhaul link design, fade margin analysis, and repeater spacing for licensed microwave links.
Radar Systems
Radar range equation (a double application of Friis) for target detection range estimation.
Use this result with related RF tools
The Friis equation is a free-space starting point for a link budget. It does not include every real-world loss, so include cable loss, polarization mismatch, connectors, obstructions, receiver sensitivity, and a sensible fade margin separately.
Get "10 RF Design Principles Every Engineer Should Know" Free
Learn practical principles for better RF circuits, PCB layouts, simulations, measurements, and troubleshooting.