Link Lab · planning model
Link Lab
Model the signal before the flight.
A theoretical free-space model, not a measurement or a guarantee. Terrain, interference, antenna orientation and local RF conditions can reduce real-world performance.
Example configuration — edit any value
The RF channel this link runs on.
Straight-line distance between transmitter and receiver.
Power at the transmitter's antenna connector.
Gain of the transmit antenna relative to an isotropic radiator.
Gain of the receive antenna relative to an isotropic radiator.
Cable, connector or other loss between the transmitter and its antenna.
Cable, connector or other loss between the receive antenna and the receiver.
The minimum signal the receiver needs, as specified by its manufacturer — enter the value yourself.
Your own planning target for margin above sensitivity — not a universal safety threshold.
Signal path
Technical details
- Free-space path loss
- Free-space path loss: 20·log₁₀(d_km) + 20·log₁₀(f_MHz) + 32.44 dB
- Wavelength
- 12.5 cm
- Fresnel zone (midpoint)
- First Fresnel zone (midpoint): √(λ·D / 4) = 5.6 m
- 60% clearance reference
- 3.4 m
- Theoretical free-space distance at target margin
- 4986 m
Obstacles near the direct path can affect the RF link even when you can visually see the aircraft. This is an engineering reference, not a terrain clearance guarantee.
Where this model's link margin would exactly meet your target reserve — not a maximum or guaranteed range.
Radio rules and allowed transmit power vary by region. Check the rules that apply where you fly.
How it's calculated
Transmit power, antenna gains and system losses combine into a predicted receive power, minus the free-space path loss the signal travels through.
Link margin is that predicted receive power minus the receiver's sensitivity — how far above the receiver's noise floor the signal is expected to be, in this model.
The target reserve is your own planning buffer on top of that margin, not a guarantee — real-world conditions this model does not see can still reduce a link with a healthy margin on paper.