There is a certain charm to older electronics gear. Heavy metal chassis and obviously hand-wired harness can be a work of art even if they would be economically impractical for most modern gear. Watching [msylvain59’s] tear down of a Collins 51R VOR receiver is a good example of that. The construction looks so solid.
If you aren’t familiar with VOR, it stands for VHF omnidirectional range and allows airplanes to tune into a fixed ground-based beacon and determine its heading in relation to the beacon. In some cases, it can also calculate distance.
Years ago, VOR antennas actually rotated rapidly, but today it is more likely to be an array of antennas switched electrically. The radio beam has several encoding schemes, including an FM reference signal that allows an airplane receiver — like the 51R — to determine the heading to the beacon. If you know the heading to two beacons, you can figure out where you are. Even with a single beacon, you can hold course towards it or away from it if you maintain a steady heading.
A receiver like the Collins would drive a Course Deviation Indicator (CDI), a Horizontal Situation Indicator (HSI), and a Radio Magnetic Indicator (RMI) on the plane’s cockpit and might also provide input to an autopilot. Compared to modern gear, the components look huge.
Understanding where an aircraft is has always been a big deal, and there are many ways to deal with it. Transponders are one part of the equation. We see a lot of hacks relating to ADS-B, too.