About this tool
Every coax cable absorbs part of the power – the more, the longer the cable and the higher the frequency. The coax cable loss calculator computes this loss for common cables such as RG-174, RG-58, H-155, RG-8X, Aircell 7, RG-213, Ecoflex 10 and 15, LMR-240, LMR-400, LMR-600 and satellite coax – or for your own attenuation value from a data sheet.
The attenuation consists of conductor losses (growing with √f) and dielectric losses (growing with f). For each cable the calculator fits such a curve through two typical data sheet values and uses it for any frequency. A comparison table shows all cables at your length and frequency, sorted by loss.
The advanced parameters add connectors and adapters, the SWR at the antenna and the transmit power: the calculator then shows the extra loss caused by the mismatch and the power that reaches the antenna. Use the cable loss directly in the Link Budget Calculator. Everything runs in your browser.
How it works
- Choose the cable type and enter length and frequency.
- Read the loss in dB and the share of power that arrives, or compare all cables in the table.
- Turn on the advanced parameters for connectors, SWR and transmit power if needed.
Frequently asked questions
How much loss is too much?
3 dB means only half of the power arrives – and the same share of the received signal is lost too. For transmitting stations 1 to 2 dB is a good target. At UHF and microwave frequencies thick cable or a shorter run pays off, for example with a preamplifier or transverter right at the antenna.
Why does the loss increase with frequency?
Because of the skin effect, current at high frequencies only flows in a thin layer at the conductor surface, so the effective resistance grows with √f. On top come losses in the dielectric, which grow in proportion to the frequency. That is why RG-58 loses about five times as much per metre at 2.4 GHz as at 145 MHz.
How accurate are the values?
The curves go through two typical data sheet values per cable. Cables from different manufacturers with the same name (especially RG-58 and RG-213) often differ by 10 to 20 %, and aged or damp cable loses considerably more. For accurate results choose “Custom value” and enter the attenuation from your cable’s data sheet.
Why does a poor SWR increase the cable loss?
With a mismatch part of the power travels back, is reflected again at the transmitter and passes the cable several times, losing power on every trip. At SWR 3 and 2 dB cable loss this adds almost 0.8 dB; with low-loss cable the effect is smaller. More on this in the SWR Calculator.