The power loss caused by a coax cable is referred to as attenuation. It is defined in terms of decibels per unit length, and at a given frequency.
Obviously the longer the coaxial cable, the greater the loss, but it is also found that the loss is frequency dependent, broadly increasing with frequency.
For virtually all applications the attenuation or loss is to be minimized. The losses in coaxial cables can be classified into:
(a) Resistive loss (b) Dielectric loss (c) Radiated loss
Of all these forms of loss, the radiated loss is generally the least important as only a very small amount of power is generally radiated from the cable. Accordingly, most of the focus on reducing loss is placed on conductive and dielectric losses.