The dispersion characteristics of a one-dimensional photonic crystal are analyzed in detail on the basis of the exactly solvable Kronig-penney model for the particular case of a periodic system consisting of an infinite number of insulator-air layers arranged in the direction of propagation of radiation. An analytical solution is obtained, and the behavior of eigenwaves near the edges of the photonic band is thoroughly studied. The behavior of roots on a complex plane is qualitatively analyzed with the use of approximate dispersion characteristics obtained via expanding the solution of the wave equation in series in terms of the harmonics of the lattice spacing. It is shown that, despite the amplifying properties of the material, no gain in the photonic band gap is present, because of the interference quenching of waves. (C) 2003 MAIK "Nauka/Interperiodica".