Martin County Amateur Radio Club logoMCARCMartin County Amateur Radio ClubK9MRTMember Login

Amateur radio tools

Feedline Loss Calculator

Estimate what reaches the antenna with manufacturer-backed cable data and phase-aware mismatch calculations.
← View all public tools

Feedline and station

Describe the cable run

? Help with this calculator
Manufacturer formula
Load information

Matched to the cable’s nominal impedance.

Power at antenna

70.54 W29.46 W dissipated in feedline

Total loss

1.516 dBMatched-only loss: 1.516 dB

Line input

1:150 + j0 Ω

Load SWR

1:1At the antenna end

ERP

70.54 WUses gain in dBd

EIRP

115.69 WERP × 1.64; referenced to isotropic

Published attenuation

1.516dB per 100 ft at 146 MHz

Data confidence

Manufacturer formulaNo generic cable-name constants

Method and sources

Know what the result means

Matched versus mismatched

Matched loss follows the selected manufacturer’s formula or documented table. Complex-load modes solve the lossy transmission-line equations using attenuation, velocity factor, length, and reflection phase. Connector, tuner, weather, installation, and cable-aging losses are not included.

ERP is not EIRP

ERP uses antenna gain relative to a half-wave dipole (dBd). EIRP uses gain relative to an isotropic radiator and is 1.64 times ERP. Neither value includes losses you have not entered upstream of this feedline.