A transmission line and radiating system measurement

Abstract

One of the major problems in mobile system maintenance is adequate evaluation of the transmission line and antenna performance. This paper describes a practical method of technique for making line loss and antenna match measurements to assure proper installation and continued satisfactory performance. Certain innovations have been incorporated in the process which are calculated to provide the maximum information with a minimum effort. The procedure consists essentially of making two transmission line input admittance measurements at widely differing frequencies. The results are plotted on a simplified version of the Smith Chart in a manner that yields transmission line loss and antenna match, These two properties adequately evaluate the transmission system for maintenance purposes. Both measurements are made at the input end of the transmission line without altering or disturbing the antenna or load end of the line. This is important where tall towers are involved or the antenna is otherwise not readily accessible. Accuracies are more than adequate for service purposes and the results are consistent under a wide variety of conditions. A simple technique for determining the distance in feet to a fault such as a break or short circuit is also described.