Tools you might need next
Calculate Standing Wave Ratio from forward and reflected power readings. Convert SWR to return loss and reflected power percentage.
Convert RF power between watts, dBm, and dBW. Calculate power density and link budget components for ham radio and wireless.
Calculate half-wave dipole and quarter-wave vertical antenna element length from frequency. Includes velocity factor correction for wire type.
Cable loss specifications are given per 100 feet at specific frequencies. Scale linearly with length. Loss increases with frequency.
Loss (dB) = Loss per 100 ft (dB) × (Length ÷ 100)Convert dB loss to power ratio. 3 dB loss = half power at antenna. 1 dB loss ≈ 79% power delivered.
P_antenna = P_transmitter × 10^(−Loss/10)Feed line loss affects both transmit and receive equally. 3 dB coax loss costs one S-unit on receive sensitivity.
Receive degradation = Same dB loss as transmitUpdated: July 2026
RG-58 loss ~1.5 dB/100ft at 14 MHz → 1.5 dB total. 100W transmitter delivers ~71W to antenna.
50 ft LMR-400 at 146 MHz: 0.9 dB loss vs 3.5 dB for RG-58 — significant improvement for weak signal work.
200 ft LMR-600 at 50 MHz: 1.8 dB loss. Compare against hardline options for permanent installations over 150 ft.
Coaxial cable attenuates RF power between transceiver and antenna. Enter cable type, run length, and operating frequency to calculate total loss in dB and percentage of power reaching the antenna.