RF Calculators
Nine everyday radio calculations, worked out as you type.
About this tool
Path loss and link budget
Free-space path loss grows with distance and frequency (20 dB per decade of each). Add antenna gains, subtract cable losses, and compare the result with your receiver's sensitivity: a 10 dB margin or more is a dependable link.
Coax loss
Loss figures are interpolated from manufacturer data (dB per 100 ft) for each cable. At 1 GHz, 10 m of RG-58 loses roughly 8 dB, more than 80% of the signal, which is why ADS-B setups use LMR-400 or mount the SDR at the antenna.
Radio horizon and Fresnel zone
VHF/UHF signals travel slightly beyond the visual horizon (k = 4/3). For a clean point-to-point link, also keep 60% of the first Fresnel zone free of obstacles.