Electronics/electrical tool package
RF Toolbox is a useful application that includes a lot of tools for antenna design and electronics/electrical calculations. It takes you step by step through the design of the antennas.
With the transmission line calculator, you can select the type of line, length, operating frequency, and calculate the losses, as well as the SWR and losses from SWR due to impedance mismatch. The load impedance can also be calculated from the measured impedance at the line input.