Introduction — Page 1, Lesson 7

We're starting a brand-new chapter, Chapter 1, "Properties of Radio Waves." This is the foundation for everything else in radio navigation, so I want to set the scene properly. Let's begin with the big picture. Radio and radar systems are now an integral and essential part of aviation. Without them, the current intensity of air transport operations would be unsustainable. Think about that for a moment. In the early days of aviation, aircraft were flown with visual reference to the ground. Flight at night, in cloud, or over the sea was simply not possible. As aircraft became more complex, it became necessary to design navigational systems that let aircraft operate without reference to terrain features. The early systems were, by modern standards, very basic and inaccurate. They gave reasonable navigational accuracy for en route flight over land, but only a very limited service over the oceans. And here's a fascinating piece of history: until about 40 years ago, flight over the oceans used the traditional seafarer's techniques of astro-navigation. That means using sights taken on the sun, moon, stars, and planets to determine position. Developments commenced in the 1910s, continued at an increasing rate during the 1930s and 1940s, and up to the present day. This led to the development of long-range systems which, by the 1970s, were providing a global navigation service. Now, here's the irony. Having forsaken navigation by the stars, the most widely used navigation systems in the last few years are once again space-based. That is, the satellite navigation systems we now take as being the norm. While global satellite navigation systems—GNSS—are becoming the standard in aviation, and many advocate that they will replace totally all the terrestrial systems, the ICAO view is different. ICAO, the International Civil Aviation Organization, holds that certain terrestrial systems will have to be retained to back up GNSS, both for en route navigation and for runway approaches. So the key takeaway here is that we're not going to see a total switch to satellites. Terrestrial systems stay as a backup. And finally, the development of radar in the 1930s allowed air traffic control to see aircraft without visual contact, which was a massive leap forward. That's the introduction. Now we're going to move into the actual physics of radio waves, starting with electromagnetic radiation. Let's go.