What is the VOR (VHF Omnidirectional Range) reference signal? I have to calculate the spectrum of this signal.

  • $\begingroup$ en.wikipedia.org/wiki/VHF_omnidirectional_range has a good description $\endgroup$ – Steve Kuo Oct 25 '17 at 15:53
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    $\begingroup$ Doppler VOR spectrum. Note for a conventional VOR, the 30 Hz reference tone modulates the 9,960 Hz subcarrier in F3 (to create the sidebands) instead of the carrier itself in A3. The modulation depth is 30%. A study of the spectrum by a radioamateur. $\endgroup$ – mins Oct 25 '17 at 17:56
  • $\begingroup$ @mins That's very helpful and complete documentation. The best answer! Thank you for finding time to help me. $\endgroup$ – Hari Seldon Oct 25 '17 at 20:17

VOR Ground Station is aligned with magnetic North. It emits two signals:

  • a 360° sweeping variable signal
  • an omni-directional reference signal

When an aircraft receives those signals, its receiver compares those and a measures the phase difference. This gives a precise radial position of the aircraft which is displayed on its Omni-Bearing Indicator (OBI), Horizontal Situation Indicator (HSI) or a Radio Magnetic Indicator (RMI), or a combination of two different kinds.

This picture shows the two signals:

enter image description here

  • Blue is 360° sweeping signal
  • Green is omni-directional reference signal
  • $\begingroup$ This is very enlightening! And also I would like to know more about this omni-directional reference signal (blue one). For example if it is sinusoidal, and all other informations for calculating its spectrum. Thank you! $\endgroup$ – Hari Seldon Oct 25 '17 at 15:42
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    $\begingroup$ Trying to fig out why they made the reference signal flash in that gif. I guess that's indicating when it's at 0° phase? $\endgroup$ – TomMcW Oct 25 '17 at 18:20

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