Investigation of Effect of Antenna Site and Antenna Type on LF Non-Directional Beacon Performance.

摘要

The reasons that out-of-tolerance needle swings are indicated by low-frequency direction-finding receivers tuned to FAA non-directional beacon transmitters are investigated theoretically and experimentally. The main conclusions are: (1) The antenna type affects only the ease of tuning and the amount of effective radiated power,but not the directional characteristics. The cage monopole antenna appears to be the best of those studied. (2) The main cause of needle swings is large terrain features. All the terrain between the transmitter and receiver affects the needle swing,so only marginal improvement can be achieved by careful site selection or site modification. (3) If all other things are equal,the size and frequency of needle swings caused by terrain decrease with decreasing radio frequency. (Author)