Based on dispersion relation of a collisional isotropic uniform plasma, the transfer function of a lossy ionospheric channel was derived. For narrow-band signals, the transfer function can be greatly simplified, and a band-limited impulse response was obtained. It was found that when the collision frequency is only a small fraction of

, the center frequency of the band, an appreciable amount of energy loss is observed. By convolution the impulse response can be used to obtain the output waveform of any other input signal transmitted through the lossy medium.