Simple question regarding coaxial cable
the data sheet of your table should provide constants for it, the formula I see often is 

$$att_{db}=(K_1\sqrt{freq})K_2freq$$  

whoever makes your cable sometimes provides their constants in the documentation so you can get an estimate. If there are none, find a similar cable an estimate with a maker that provides them. Usually they end up giving you a value per unit of length.

I really do not know how to write equations properly on here.