Dispersion of h.f. pulses by ionospheric reflection

An approximate expression is presented which gives the duration of an electromagnetic pulse formed by the spectral content in an h.f. bandwidth received after reflection in the ionosphere. The variation of the pulse duration with the bandwidth and a coefficient of the propagation path is shown. Methods of estimating the propagation-path coefficient are discussed. The geomagnetic field is omitted from the computation. Digital computations for a more realistic case than that on which the approximate expression is based are given for comparison.