Cable loss & antenna calculator
Calculate coax attenuation, power arriving at the antenna, additional feed-line losses, antenna gain, ERP and EIRP. The integrated cable database contains dozens of common amateur-radio coax types.
From the transmitter to the radiated signal.
Choose a cable, operating frequency and length. Antenna gain is optional. Values are recalculated immediately in your browser.
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Compare several coax cables under exactly the same conditions.
Select up to eight cables. Frequency, length, transmitter power, additional losses and antenna gain are taken directly from the calculator above so the comparison remains fair.
| Cable | dB / 100 m | Cable loss | Total loss | At antenna | Efficiency | EIRP | vs. best |
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Get three cable recommendations for your station setup.
Choose one or more bands, tell the tool the length and how many connectors or couplers you expect. The assistant then suggests three suitable cables based on the measured loss values in the database – without any price ranking.
Select one or more bands and start the recommendation assistant to get three suitable cables.
How the same cable behaves across the amateur bands.
The table uses your current cable length, power, extra loss and antenna gain.
| Band | MHz | Cable loss | At antenna | EIRP |
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Loss is measured in dB.
Coax attenuation and connector losses are logarithmic ratios. 3 dB loss means roughly half the transmitter power reaches the next point in the system.
Antenna gain is different from cable loss.
dBi references an isotropic radiator; dBd references a half-wave dipole. The calculator converts between them with 2.15 dB and uses dBi for EIRP.
Radiated reference power.
EIRP combines transmitter power, feed-line losses and antenna gain referenced to an isotropic antenna. ERP uses a half-wave dipole as the reference.
A practical estimate, not a laboratory certificate.
The database uses published typical attenuation values from cable manufacturers and specialist dealers, including Kabel-Kusch, WiMo/SSB Electronic and Times Microwave Systems. Real loss changes with temperature, connectors, installation, cable age, moisture and manufacturing tolerances. For frequencies between published points the calculator interpolates the attenuation.
Cable loss, gain and power – briefly explained.
Why can 100 W become much less at the antenna?
Coax loss increases with frequency and length. A cable that is excellent on HF can lose several dB on 70cm or 23cm.
Does antenna gain restore the lost watts?
No. The cable loss physically reduces the power arriving at the antenna. Antenna gain describes how the available power is concentrated in particular directions.
What is the difference between dBi and dBd?
0 dBd corresponds to about 2.15 dBi. dBd references a half-wave dipole, while dBi references an ideal isotropic radiator.
Can I use a cable that is not in the list?
Yes. Choose “Custom cable” and enter the manufacturer attenuation in dB per 100 m for your operating frequency.