Chapter 1 Wireless Direction-Finding Fundamentals Benjamin Friedlander 1.1 INTRODUCTION Wireless direction finding has a long, and distinguished history going back to the very beginnings of wireless communications around the turn of the twentieth century. Many of its basic concepts had been established by that time. To put this in perspective we quote the opening sentence of the Foreword (by T. L. Eckersley, F.R.S.) to a book first published in 1922 entitled Wireless Direction Finding (Keen, 1938):