How VORs Really Work

Flight instructors across the nation have been involved in a massive coverup scheme surrounding VOR stations. We’ve all been taught to think of VOR stations as a giant compass rose transmitting radio beams in 360 directions. It is common to refer to a VOR as a giant wheel with 360 spokes representing radials. These are all lies. 


Well, not exactly. All conspiracy theories aside, flight instructors have been telling this story for a good reason, it is much easier for pilots to conceptualize a great spoked wheel in the sky than to understand the inner workings of the machine.

It’s the age-old “black-box” argument. It is far more important to be able to use a VOR than to know how it works. That being said, a VOR is a surprisingly simple device.

VOR stations are nothing more than the radio equivalent of a rotating beacon with a flashing strobe. To conceptualize the system, consider the following simplification:

The omnidirectional signal pulses as the unidirectional signal passes north.

The omnidirectional signal pulses as the unidirectional signal passes north.

Each VOR consists of  red unidirectional rotating beacon and a white omnidirectional strobe. The rotating beacon turns at a rate of one degree per second, so that it makes one complete rotation every 360 seconds. Every time the beacon passes through north, the strobe flashes white.

By comparing the time between beacon and strobe flashes, the airplane’s onboard equipment can determine the current radial. For example, if it you were to see a white flash followed by a red beacon 45 seconds later, then you would be on the 45 degree radial from the station.

The VOR system works in exactly this way, except that it uses unidirectional and omnidirectional radio signals instead of beacons and stobes. For accuracy, the unidirectional signal, our “beacon,” rotates at a dizzying 1,800 r.p.m.

Helpful Links:
VOR / ADF Navigation Simulator
Wikipedia’s Article on VORs


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About the author
Pat Flannigan is a professional pilot and aviation blogger. He has been flying for fifteen years and is currently working as an airline pilot in the United States.

12 Replies to How VORs Really Work

  1. Paul says:

    Thanks for the very informative article. I learn something new everytime I visit your site. Keep up the good work, it looks GREAT!

  2. Very neat explanation. Although one doesn’t need to know the details it certainly is quite interesting.
    Thanks for the article.

  3. Can you add my blog to your list? I certainly would appreciate it.

    W. Erston

  4. I am a serious Flight Simulator pilot and I have really worked hard to learn all about the Nav Aids-VORs, NDBs Inter sections etc., given out in the respective programmes’ Learning Centers as a beginner in the FS world and was not satisfied at all just by learnig to fly the FS planes. I believed the the articles written about the VORs and their functioning and usefulness in those lessions.
    This article of yours about the VORs and how they actually function is a wonderful nice thing. Now it is a very easy to understand and grasp the essence of VORs working,Sir. Now I feel that I am a truely better enlightned FS pilot than what I was before. ( I have taken the Private Pilot Certificate, Commercial Pilot Certificate, Instrument Flight Rating Certificate and the Airline Transport Pilot Certicate in a quite popular FS programme which I loved and still love a lt.) I am really lucky to have stumbled on this nice article of yours.
    Thanks,
    M.S.Murugesan.

  5. Greg. N. Jon says:

    Just a heads up, this article is wrong. You said
    “The rotating beacon turns at a rate of one degree per second, so that it makes one complete rotation every 360 seconds.”
    In truth, the directional signal rotates at 30 Hz, or 30 revolutions per second. The directional signal, not the omnidirectional signal, rotates at a “dizzying 1,800 r.p.m.”
    Furthermore, I think you were thinking about the 30 Hz frequency modulation of the omnidirectional signal when you said “For accuracy, the unidirectional signal, our “beacon,” rotates at a dizzying 1,800 r.p.m.”. By definition, an omnidirectional signal doesn’t rotate.
    Source: Undergraduate degree in EE, wikipedia.org.

    • Thanks Greg, I think we’re talking semantics on the same principle. I was trying to make an analogy to make it easier to understand, hence the slow rotating beacon (directional signal modulating at 30 Hz) and strobe (omnidirectional signal) example.

      • Greg. N. Jon says:

        Hey Pat. I understand the desire to make a complicated thing simple, but the problem is that the information itself is wrong. A question on my final exam in my Electronic Navigation Theory class is to explain why your article is wrong.
        The fact of the matter is that VOR is very complicated. There is simply no way to explain phase modulation without a background in electrical engineering. I like your lighthouse analogy, but it is really no better at explaining VOR than the “great spoked wheel in the sky.”

        • Greg N. Jon says:

          One last thing. Upon closer inspection, I can see that you said unidirectional signal rotates at 1,800 r.p.m. That was my mistake in assuming you said omnidirectional. The problem is with the earlier paragraph in which you said the beacon rotates slowly. Perhaps if you rewrote that paragraph to explain that that is just a way to conceptualize the workings of VOR? The reason I say this is that this ehow article (http://www.ehow.com/how-does_5522066_vor-stations-work.html) seems to think your first paragraph is correct.

  6. Howard says:

    I’m an electronic engineer with an interest in aviation, especially navigation systems and I explain it like this.

    Fixed carrier at VHF (108/115MHz) with morse ident plus rotating carrier at 30Hz. The phase difference between the fixed and rotating signals at the receiver is proportional to the bearing of the aircraft relative to the array.

    Admittedly you need a bit of electronic background for it to make sense and it is no doubt more complex than this, but it helps me understand the basic concept of a VOR transmitter.

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