The Influence of Trees on Television Field Strengths at Ultra-High Frequencies

Field studies of UHF wave propagation between television transmitting and receiving antennas indicate that typical woods are essentially opaque at these frequencies. The signal in the presence of woods near the receiving antenna appears to be principally that diffracted over the trees, with a small residual "leakage" field observable where the diffracted fields are very weak. The results of measurements are compared with diffraction theory, and the attenuation below free space fields due to the woods is found to be in good agreement with that predicted for a spherical obstacle having a four-thirds earth\´s radius. The conclusions are applied to the estimation of average losses in large areas.