Free tool
Dipole & Feedline Calculator
Compare feedline types, see the loss in dB and the power that actually reaches the antenna.
Feedline loss is the quiet tax on every station. This calculator compares common cable types at your operating frequency and length, shows how many decibels and how many watts you are losing, and tells you when the loss is high enough to justify a different cable or a different approach.
Inputs
Result
Power reaching the antenna--W
Enter values to calculate.
Feedline loss-- dB
Power lost as heat-- W
Dipole length for this band-- m
Balun required--
Loss as a share of your power--
Loss scales with frequency and with length, and is quoted in dB per 100 m at a reference frequency.
A loss above 3 dB means more than half your power is heating the cable.
Balanced feedline into an unbalanced radio always needs a balun.
A loss above 3 dB means more than half your power is heating the cable.
Balanced feedline into an unbalanced radio always needs a balun.
What this calculator returns
Feedline loss in dBPower at the antennaSuggested cableBalun requirement
These figures are calculated from standard formulae and typical published component data. They describe an ideal installation, not yours. Measure your own antenna before cutting wire, and confirm any figure against your equipment and local regulations before relying on it.
Feedline loss reference
| Cable | 3.5 MHz | 14 MHz | 28 MHz | 144 MHz |
|---|---|---|---|---|
| RG-58 | 0.7 | 2.2 | 3.4 | 14.0 |
| RG-8X | 0.5 | 2.1 | 2.6 | 8.0 |
| RG-213 | 0.3 | 1.0 | 1.5 | 4.5 |
| LMR-400 | 0.2 | 0.6 | 0.9 | 3.4 |
| Ladder line | 0.1 | 0.2 | 0.3 | 1.2 |
Reading the tableFigures are typical published values for a matched line at 30 metres. Add roughly 20 percent for a 2:1 mismatch, because the reflected wave makes a second pass through the same cable.