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i KNOW THAT 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 it can know its position and radial.

My question is, is it possible the aircraft receive only the reference signal??? Making the pilot know the direction to the station and not the radial he's on.

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    $\begingroup$ As Adam says, the "lighthouse" analogy is a very neat and intuitive analogy, but it is just that. The actual operation of a VOR is not quite as intuitive. Watch the first five minutes of this really good video for more. $\endgroup$
    – randomhead
    Aug 11, 2022 at 22:51
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    $\begingroup$ With an Radio Magnetic Indicator (RMI) tuned to a vor station its needle will point directly to the vor station. The needle is superimposed on a directional gyro and the tail of the needle will identify the radial the aircraft is on. Hypothetically if the directional gyro was broken and did not move the needle would still point directly to the vor showing the relative angle between the aircraft's nose/heading and the vor. $\endgroup$
    – user22445
    Aug 11, 2022 at 23:20
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    $\begingroup$ To 757toga's point, you CANNOT know the direction to the station and NOT know which radial you are on. It's like saying that you want to know which way North is, but not know which way South is. For that reason your question really doesn't make sense. $\endgroup$
    – Michael Hall
    Aug 12, 2022 at 2:12
  • $\begingroup$ Further to 757's and MH's point... Yes, you could build a direction-finding antenna and sense the direction of the VOR from you. But a DF antenna requires either a phased array or, like ADFs, a motorized dipole loop. Manufacturers don't do that, because no one would buy it, because it's antithetical to the design purpose of VOR. It's adding cost and complexity for no benefit. But no, there is no technical reason at all why it couldn't be done or wouldn't work. It's just a feature that no one wants, and therefore not viable to build into a certificated product. $\endgroup$
    – Max R
    Aug 27, 2022 at 22:26
  • $\begingroup$ "Making the pilot know the direction to the station", we cannot determine the bearing of the reference signal, the VOR receiver antennas are not directional, contrary to an ADF. This is why a second signal is required. See this question or this one. $\endgroup$
    – mins
    Sep 4, 2022 at 16:40

1 Answer 1

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You have a misunderstanding about the operation of the VOR. From the phase of the two signals it is possible to determine the radial, but not the location of the receiver (or distance). In order to get the distance it is necessary to use DME. DME can be colocated with a VOR so at times they might be (technically incorrectly) used interchangeable. I suppose it would be possible to construct a directional radio receiver, similar to an NDB receiver, that attempts to find the direction to the VOR. But, I've never seen a VOR receiver that is able to do this. Any VOR that I've worked with requires the both signals, and then uses the phase difference between them to determine the radial.

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  • $\begingroup$ +1 "I suppose it would be possible to construct a directional radio receiver", actually you just need a directional antenna and examine the signal strength for all azimuths. $\endgroup$
    – mins
    Sep 4, 2022 at 16:48

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