User enters frequency in GHz, Er & Ur, pushes the "Calculate" button and this app calculates phase velocity, wavelength and impedance. As an example, enter 3 for GHz, 7 for Er and 3 for Ur, then push calculate. This should result in 6. 547E7 m/sec for the phase velocity, 0. 0218 m for the wavelength and 246. 9 Ohms for the impedance.