I'm VFR inbound to a controlled airport on a day with a high thin overcast. Beautiful day for flying: no glare, little turbulence, old snow still sparkling on the ground below, but the runways and taxiways perfectly clear. The controller tells me to call ten miles out and asks another aircraft to report "over the OMNI."
How retro. The OMNI? I think the term might be more common in the US than Canada, but it's still pretty old fashioned. Omni means all. A moment here for the non-pilots, because I think I've left them behind in a cloud of terminology a few times recently, and because I still remember the thrill of excitement I felt on first learning how the thing I'm about to explain works. It was like a grade nine physics class come to life and become useful. There's a thing in aviation called Very High Frequency Omnidirectional (Radio) Ranging. Very High Frequency is always and already abbreviated VHF, which is already a type of radio, hence the thing itself is called a VOR. ("Vee-Oh-Arr").
A VOR is two things, one that's on the ground and sends signals and one that's in your plane and receives, interprets and displays the meaning of the signals. The one the air traffic controller referred to was obviously the ground-based one. It sends a VHF radio signal on a published frequency. You know that a radio waves are depicted as squiggles, sine waves oscillating from start to finish, a little repeated radio shape at frequency times per second. That's what frequency means. Now this is the cool part. The same frequency signal is sent out twice. Once starting at the same point all the way around and the second time starting at the same point at north, but offset by one three-hundred sixtieth of the cycle for each degree of the compass away from north the signal is sent.
Now the percentage of you that know how VORs work are either bored or laughing at my obsession with these. It's probably the fifth time I've explained this now aged technology on my blog. And those of you who let your eyes glaze over at anything math or physics related are waiting for this paragraph to be over. But if there's one reader who didn't know this simple, brilliant navigation solution and is now about to grasp it, it's worth boring everyone else. Because the VOR receiver in the airplane measures the difference in phase (how many three-hundred-sixtieths, i.e. degrees, different the two signals are) and displays it as a needle swing. (Nowadays it can be displayed digitally, too, but that's not the super cool part). Do you see it? The difference between the two signals is the bearing from the ground station to the receiver.
I'm sorry if that was never the coolest thing you'd ever heard. I promise to find a more modern piece of technology to rave about soon. But nothing is as elegant anymore, now that everything new has a computer in it. Computers are amazing, but they don't have the simple brilliant simplicity of an airspeed indicator.
Hey look, this flight sim site agrees with me. "The VHF Omnidirectional Range navigation system, VOR, was probably the most significant aviation invention other than the jet engine." True! Jet engines are so amazing that they sound almost as impossible as this perpetual motion air car, but jets are real.