Radio Range & Sensitivity Calculator

Uses a hybrid Friis + environment model. Choose whether to solve for maximum range or required receiver sensitivity at a given distance.

Inputs & Results

Mode:

TX Power (dBm) TX Antenna Gain (dBi) RX Antenna Gain (dBi) Frequency

Receiver sensitivity (dBm) Fade margin (dB)

Environment

Result will appear here.

FSPL

—

Env. loss

—

Total path loss

—

Rx power

—

Link margin

—

Hybrid model: PL = FSPL + L_env, where FSPL is ideal free-space path loss and L_env is an empirical environment offset (urban, indoor, foliage, etc.).

Theory (Friis & Link Budget)

Free-space path loss (FSPL):

FSPL(dB) = 32.44 + 20·log₁₀(d_km) + 20·log₁₀(f_MHz)

Hybrid model used in this tool:

PL_total(dB) = FSPL(dB) + L_env

where L_env is a constant term (e.g., +18 dB for urban, +25 dB for dense urban) capturing extra loss due to buildings, foliage, clutter, etc.

Receive power and sensitivity:

P_RX(dBm) = P_TX(dBm) + G_TX(dBi) + G_RX(dBi) − PL_total(dB)

P_RX ≥ S_RX + M_fade

The margin M_fade represents fading, interference, and implementation loss. Range mode inverts this inequality to find the maximum distance.

Range solution (analytical):

FSPL_allowed = P_TX + G_TX + G_RX − (S_RX + M_fade) − L_env

d_km = 10^{ (FSPL_allowed − 32.44 − 20·log₁₀(f_MHz)) / 20 }

Real-world links also depend on antenna height, Fresnel zone clearance, polarization mismatch, multi-path fading and many other factors, so this calculator should be used as a first-order design / teaching tool rather than a guaranteed coverage predictor.

Example Ranges (FS environment, 0 dBi antennas, 10 dB margin)

Freq (MHz)	TX Power (dBm)	Sens (dBm)	Margin (dB)	Max range (km)