  We examine the feasibility of using medium resolution spectra for determining
the parameters of atmospheres of hot stars by means of numerical simulations.
We chose the star Cyg OB2 No7 as a test object and obtained its spectrum
(\lambda/\Delta\lambda=2500) with Russian-Turkish RTT150 telescope. The CMFGEN
code was used to construct a model of the atmosphere of Cyg OB2 No7. For the
first time we have detected the NIV \lambda\lambda 7103.2-7129.2 lines in the
spectrum of this star and used them to determine the physical parameters of the
wind. The rate of mass loss measured using the H$\alpha$ line exceeds the loss
rate measured using lines formed in the wind. This indicates that the wind is
nonuniform, apparently due to rotation.
