As aviation grew by leaps and bounds during the 30's, 40's, the letters "A" and "N" played a very important part in development of aviation. What part did they play?
Since I am going to be camping over the Memorial weekend with my lovely bride to be someday, (I hope), I'll go ahead and answer this!
During the growth of aviation during the early years, not much in the way of electronic navigational aids were available to pilots. As the U.S. airmail system begin to be developed, the early years, "Wiley Post", Lindberg and other famous aviators were actually guided by fires built by farmers, which were paid by the U.S. government, from city to city. As things begin to be developed in radio, a low frequency radio system was installed throughout the U.S. A transmitter was installed, which generated a "4" legged range. Each leg of this range transmitted an "A" and a "N". The signal produced was in Morse code, dot dash and dash dot. One side of this leg was the "N" quadrant and the other side of the leg was the "A" quadrant. If you were directly on the leg, the "A" and the "N" were overlapping and you would hear a steady tone, which would signal that you were on course. This is were the movie term, "riding the beam" came from during the 40's.
Since you could only hear a signal in your ears and had no instrument as yet which would assist you in navigation, you had to work "range" problems by ear. Example, if you tuned a station, you had to first figure out if you were flying towards the station or away from it. You did this by turning your volume way down to where you could barely hear it, took up a heading and listened. If the signal grew in volume, then you were generally flying towards the station, if signal volume disappeared, you were going away from the station. Then came the problem of figuring out where the station was and this was called a range orientation problem. I won't go into a lot of detail at this point, but the whole object of the range orientation was to find one of the line of "null" or legs, bracket it back and forth until you determined if you were going towards it or away, then it was a simple matter of Ident the station, pull out a C&G chart, shoot the approach and wala, you were home free. Only two problems remained before landing safety! Hope you had at least a 600 foot ceiling on clouds and hope you didn't run out of gas working your range problem.
