VHF propagation measurements in the Rocky mountain region

Abstract

Mobile measurements of VHF propagation over various irregular terrain paths have been made by the National Bureau of Standards in the Colorado Rocky Mountain region in an effort to evaluate terrain effects upon broadcast and point-to-point communications at very high frequencies. Mobile measurements of the varying path transmission loss were obtained in a continuous manner while driving along selected routes with a mobile field strength recording unit, which consists of a modified house trailer equipped with a telescoping mast and pulled by a pick-up truck. The paths used ranged from relatively smooth to very rough. The results of the measurements are considered in the light of current irregular terrain theory. The correlation of Sector median transmission loss for different frequencies over irregular terrain tends to be high when the paths are nearly the same, becoming significantly less when the paths diverge. This would indicate that the frequency selectivity of an irregular terrain path is small.