AbstractThe electromagnetic similitude concept where the real and imaginary parts of the propagation factor, times the linear-dimension squared, are held constant in the simulated and actual media to maintain the same geometric distribution of the field, except for different scale factors, is well known. Such a concept has been effectively utilized in the past to determine experimentally, with a model, the long-range electromagnetic propagation characteristics from sources above or below the earth’s surface for various earth-atmosphere discontinuities. An effective simulation model of the earth-ionosphere waveguide can also be built such that it satisfies the classical simulation of earth-atmosphere interface but only matches the reflection-coefficient at the ionosphere. Theoretical requirements for models for the long-range ELF and VLF propagations, and experimental data obtained from the models for the ideal day-time ionosphere and for ionosphere non-homogeneities resulting from abnormal ionization are presented in this paper. Carbon impregnated foams with different dielectric constants and conductivity distributions and salt water with various salt concentrations to simulate the required conductivity distribution have been used to model the ionospheres.