TABLE OF CONTENTS Chapter 3 presented the most popular types of antennas in current use for passive direction finding. It is not always clear why a certain design or system has been chosen, so emphasis has been placed on the key features of the designs. The actual antenna choice will generally be dictated by the system, the required accuracies, and the cost.
A DF system can almost be made as accurate as desired if sufficient antenna aperture is available. The driving factors, however, are the available geography for the DF system, the host vehicle requirements, and the mission needs. For simple determination of locations, line of bearing accuracies of 8 10 degrees peak are usually good. For targeting or aiming, accuracies of better than 2 degrees are required. For high-gain electronic countermeasures (ECM) or jamming, fractional accuracies are needed. In these cases the accuracy must be developed by signal processing both by analytical means and by digital or processing means. We shall study both methods in the chapters that follow.
