recording of four-course radio range
AV8,
Can't help you directly but as a technology historian (though not, I must confess, a 'real' pilot) it occurs to me the four-course system is in many respects a direct predecessor to wartime navigation devices such as OBOE. OBOE was devised in the UK in the early 1940s by Alec Reeves who had earlier invented Pulse Code Modulation, the basis of all digital transmission systems. It used two base stations that measured the distance between them an an aircraft. One created an 'arc', centred on the station and designed to pass directly over the target. The other measured the pilot's position on that arc and hence his nearness to the target. Rather like the four-course system, tones and morse signals were used to tell pilots if they were on course. The 'correct' note was said to sound like an Oboe - hence the system's name. A few years ago, I made a TV programme about OBOE that starred then-RAF pilot 'DReg' Bhasin (now, I think a member of the RAF Flight but he may correct me). I suspect it may have been broadcast in the US. Would welcome any comments from others as I am currently researching early navigtaion systems and the development of radar. David