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Friis Transmission Calculator
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.
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