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Vegetation Loss Measurements at 9.6, 28.8, and 57.6 GHz through a Pecan Orchard in Texas.

Abstract : Vegetation loss studies conducted for this report were a continuation of work reported in U S Army Report CECOM-81-CS020-F entitled, SHF-EHF Propagation Through Vegetation on Colorado East Slope. These measurements at 9.6, 28.8, and 57.6 GHz, emphasize determining signal properties as a function of foliage depth in order to support the development of a model for predicting link performance. An evenly planted pecan orchard near Wichita Falls, Texas, was selected as the test area, which permitted controlled measurements to remove the density variability normally found in forested areas. In both the foliated and nonfoliated state, a sequence of measurements was made for an increasing number of trees in path, starting with one tree. For each path, azimuthal and elevation angle scans were made at terminal heights of 1, 4, and 6 meters. Additional tests, allowed determination of propagation characteristics associated with the position of the transmitter and receiver relative to a group of trees, as the transmitter was moved (position scanned) along an arc at the edge of the orchard. An abrupt change in rate of loss with tree depth in the presence of leaves, occuring between 30 and 80 meters is believed explainable by the transition from direct ray to a propagation mode where multiple scattering produced a lower loss rate. (Author)