THE JUNGLE AS A COMMUNICATION NETWORK (REVISED)
DEFENSE RESEARCH CORP SANTA BARBARA CA
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Elementary arguments and a simple model are used to clarify the dominant features of radio transmission through jungles. Part I represents the jungle as a plane uniform slab of constant conductivity and permittivity. A critical frequency is defined below this frequency the slab behaves like a conductor above it, it behaves like a dielectric. From these two limiting cases an upper limit on attenuation, which holds independently of the operating frequency, is derived. The model is applied to Herbstreits experiments in the Panama jungle. Reasonable assumptions regarding the dielectric constant and density of the jungle lead to values between .02 and .04 mhosm for the conductivity of the vegetation, which corresponds quite well with that of moist earth. Part II discusses the applicability of the uniform dielectric model employed in Part I. Equivalent circuit concepts are used to analyze the jungle as a four-terminal network. The model of Part I is shown to be strictly applicable only to a uniform--or at least a symmetrical--jungle. The determination of the network parameters for the equivalent circuit representing the jungle is discussed. The relation between the complex propagation constant and the amplitude of the forward scattered field is given. The results of using the Born approximation, and a rough first correction to it, to solve the field problem are also stated.
- Radio Communications