Coax cable

Use the cable datasheet’s attenuation at the operating frequency. After converting it to $a$ in dB/m, multiply by length $\ell$ in metres to get total matched loss $L$ in dB:

With matched source and load, subtract this loss from input power in dBm to obtain output power in dBm. Changing frequency in the tool changes electrical length, but does not update the attenuation you supplied.

Velocity factor VF gives wave speed as a fraction of light speed $c$. The one-way delay $\tau$ in seconds follows from distance divided by that speed:

At frequency $f$ in hertz, the wavelength inside the cable is $\lambda_g=\mathrm{VF}\,c/f$ metres. The model keeps VF constant and excludes dispersion, bends, connectors, temperature changes and mismatch.

The loss-budget length is the allowed loss divided by attenuation per unit length. Zero attenuation gives no finite loss-limited length in this model. Length and frequency tolerance checks vary one input at a time; they do not combine installation uncertainties.

The power-flow bar compares power entering the cable with the fraction reaching its matched load. It is not a power-versus-position plot. Without an input-power value, its endpoints use a normalized 100% input. The example attenuation is illustrative, not a specification for a particular cable.

Generated values from unit changes or the loss-budget calculation display at most two decimals; calculations and copied input values retain their full precision until edited.