Talk:VHF omnidirectional range

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"VORs are quickly being ignored in favour the much more user-friendly GPS system, and it is generally thought that they will be turned off around 2010. Oddly the airways have become so important to air traffic control that aircraft are forced to follow them even when they are using GPS for navigation."

This is a rather contentious statement, and contains some POV remarks "Oddly...". Nothing odd about it. VOR cannot be "ignored", since as yet GPS is not necessarily actually admitted as a primary means of navigation in many territories. In addition, GPS receivers that are approved for use for aerial navigation are very expensive pieces of kit - the cheap handheld and mobile units are not considered good enough for aircraft use. Thousands of GA aircraft do not have GPS, nor are ever likely to, yet many are fitted with VOR equipment. As a pilot, I have never heard that VOR is likely to be switched off, just as NDB have not been switched off despite being superceded decades ago. Unless you can point to a reliable source for this factoid, I for one am inclined to take it with a very big pinch of salt. Since it's also opinion-laden, I will remove it from the article until it can be verified and reworded.Graham 13:32, 23 Apr 2005 (UTC)

Contents 1 Possible incorrect link in text of VOR description. 2 Requested move to VHF Omnidirectional Range 3 Flight Director 4 Operational description in error? 5 Accuracy 6 ILS subsection 7 Internationalized

[edit] Possible incorrect link in text of VOR description.

Thanks for this excellent explanation of VOR (VHF Omnidirectional Range)! However, in the first sentence of the last paragraph of the sub-section titled "Using the VOR", the words "flight director" are intended to refer to a computer on the airplane but they link to a Wikipedia page describing the Chief of Flight Operations for a NASA space mission.

I'm a novice here, so I haven't made any changes regarding this possible incorrect link. Perhaps a more knowlegable contributor can check/fix this.

Thanks for creating and maintaining this excellent encyclopedia!

Steve-vts -- Sept 13, 2005

I have removed the incorrect link to flight director Sfisher 23:08, 13 October 2005 (UTC)

[edit] Requested move to VHF Omnidirectional Range

• Oppose Capitalization may be a convenient way to clarify the abbreviation VOR, but this is not a proper noun and should remain in lower case. —Michael Z. 2005-10-19 18:40 Z

• Oppose Just because an acronym is often capitalized, that doesn't mean the spelled out version should be. The capitalized acronym in the introductory paragraph as it should be, though it should probably follow rather than precede the spelled out version, which need not be capitalized nor hyphenated. Gene Nygaard 05:19, 21 October 2005 (UTC)

• • Result: 2-1 against page move: page not moved. Eugene van der Pijll 18:28, 29 October 2005 (UTC)

[edit] Flight Director

"Electronics can solve this problem, and the flight director makes such tasks almost foolproof. A flight director is an analog computer..."

The Flight Director is an analogue or digital computer that represents navigational data on the Attitude Indicator as an attitude and angle of bank or rate of turn to fly.

The term you need is "Area Navigation System" which has the slightly bizarre acronym "RNAV": this being an analogue or digital computer system that in its most basic form uses VOR/DME signals to allow direct flight to/from points other than the VORs themselves (these points in the basic equipment are defined as radials and DME distances from VOR/DMEs and are known as 'ghost stations'). Very advanced digital Area Navigation Systems use input from many other navigational sources and do lots more besides and are known as Flight Management Systems.

Corrected, and removed some other related text that was incorrect.

BaseTurnComplete 22:32, 6 January 2006 (UTC)

[edit] Operational description in error?

The article currently says, "The combined signal is fed to an array of four omnidirectional antennas, which rotates the signal at 30 times a second." I've always thought that the carrier signal is radiated in all directions simultaneously and the subcarrier (and only the subcarrier) is rotated as its phase changes. Again, I'm not completely sure of this, thus the discussion rather than an outright edit. However, I would think that, if the article as it stands is correct, there would be a pulsing effect to the received morse identifier (the 30Hz rotation), and this doesn't happen. ChadScott 22:27, 8 June 2006 (UTC)

That whole paragraph might need a bit of rewording. http://www.navcen.uscg.gov/pubs/frp2001/FRS2001.pdf page 81 of 126 has a brief description:

"A VOR transmits two 30 Hz modulations resulting in a relative electrical phase angle equal to the azimuth angle of the receiving aircraft. A cardioid field pattern is produced in the horizontal plane and rotates at 30 Hz. A nondirectional (circular) 30 Hz pattern is also transmitted during the same time in all directions and is called the reference phase signal. The variable phase pattern changes phase in direct relationship to azimuth. The reference phase is frequency modulated while the variable phase is amplitude modulated." (PD-US-GOV)

I'm pretty sure the 1020 Hz ident (and sometimes voice ident) is/are transmitted periodically on the carrier output, along with the reference signal (which is omni-directional, non-rotating and equal amplitude in all directions). The electronically rotated pattern is transmitted via the same four antennas and fed via a sideband 1 and sideband 2 signal. Don't ask me for a source for that or how to incorporate any of the above into the article. I'll try to find something on the net later. -Dual Freq 03:06, 9 June 2006 (UTC)

I've reworded the article a bit to make this clearer to the reader. ChadScott 05:57, 13 June 2006 (UTC)

I think it's worse now, from above: "The reference phase is frequency modulated while the variable phase is amplitude modulated." (PD-US-GOV) FM is the 9960 Hz which is the reference, AM is the cardioid / rotating pattern. --Dual Freq 11:10, 13 June 2006 (UTC)

I believe I've fixed the paragraph, bottom line from the FAA source above is the reference is 30Hz FM and the variable is 30 Hz AM. Right now all I can cite as a source is the above paragraph and what's in my head (which may not be an acceptable source). I'll look for a net source, but I don't know if I can find one. However, I'd rather pull the whole paragraph than leave it with something that's not correct, what's in there now is as correct as I can be with no other sources. --Dual Freq 00:33, 14 June 2006 (UTC)

I think this is close, but I'm still not sure it's totally correct. The variable signal is on the subcarrier, isn't it? In other words, the morse-code ID and reference 30Hz tone are omnidirectional FM and the variable rotating signal is AM on a 9660 subcarrier? ChadScott 07:13, 14 June 2006 (UTC)

I think this backs me up, the 9960 Hz if FM modulated by 30Hz ref. Then that is AM to the carrier. "A 30-Hz fixed-phase reference signal (0°-Magnetic North) is frequency modulated on a 9960-Hz subcarrier and then amplitude modulated to the operating rf frequency of the station. A 30-Hz variable phase signal (representing 0° to 360°) is directly amplitude modulated to the same rf frequency. The two audio tones are detected from the received VOR rf; the phase of the reference signal Is corrected for a selected course other than 0°, and the two signals compared. The difference between the two indicates the angular deviation of the aircraft from the selected course."TM-11-1510-213-34 (PD-USGov-Military-Air Force) Lower font size in browser if the linked page is hard to read because of overlapping text. The ref says directly AM to the RF carrier, but I've always heard it described as space-modulation via the sideband signals meaning the modulation occurs somewhere other than the transmitter, but to the aircraft receiver it still modulates the carrier amplitude, so I guess it is AM. If this modulation were visualized, it would look like a cardioid pattern rotating at 30 Hz. The phase of the two 30 Hz signals is what is compared, not the amplitude. --Dual Freq 11:12, 14 June 2006 (UTC)

[edit] Accuracy

I added the accuracy standard ARINC 711 reference. This standard is the most difficult to obtain but it is possible and can be far better using an optimal receiver algorithm. --bloublou 18:03, 7 August 2006 (UTC)

As stated in the article. 1.4 degree system accuracy per FRS that is cited. That probably includes the .4 ARINC specifies for reciever equipment and 1.0 FAA uses for ground based transmitter equipment. Ground based VORs are monitored with a +/- 1 degree tolerance and will shutdown if they exceed it. Dual Freq 22:14, 7 August 2006 (UTC)

[edit] ILS subsection

I removed the ILS subsection as VORs and ILS work completely differently. Calling an ILS a "narrow" VOR is an inaccurate simplification. ChadScott 01:40, 13 January 2007 (UTC)

[edit] Internationalized

I've pruned quite a bit of US-specific stuff and internationalized other stuff accordingly. To our American friends: you're not the only English speakers in the world, nor does the world end at your borders. Please try to bear this in mind when editing articles that are not inherently US-specific!BaseTurnComplete 09:25, 31 January 2007 (UTC)