Where can I find the range of VOR's?

jasc15

jasc15

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I haven't seen anything in the A/FD that specifies the range of a VOR, so how can I tell at what distance a reliable signal can be acquired?
 
In the airport entry for the nearest airport, under the 'aids to navigation' heading, the VOR should be listed, with a (T), (L), or (H) for Terminal, Low, or High, respectively. The standard service volumes for those are listed in the AIM.
 
Chuck- that's good to know. For off-airport VORs, they can be looked up in the AFD and the same information is available too.

Thanks much!
 
jasc15 said:
I haven't seen anything in the A/FD that specifies the range of a VOR, so how can I tell at what distance a reliable signal can be acquired?
Click to expand...

In addition to the range quoted in the AIM, there is another constraint that isn't always obvious.

A VHF signal travels line-of-sight. That is, if you can't "see" the VOR below the horizon, you can't navigate on it reliably either . How do you calculate radio horizon? Pretty simple.

d = sqrt (2*h) where d is the radio horizon in miles and h is the AGL DIFFERENCE between the VOR altitude and your altitude. In the flatlands east of the Rockies most of the land is at about 400' MSL. If you are flying, for example, at 4500' MSL you are at 4100' AGL.

2 * 4100 = 8,200. Square root of 8,200 is about 90 miles. However, if you are putting along at 2500 MSL, range drops to about 65 miles.

Just FYI.

Jim
 
If you are flying published routes at or above MEA, the VOR range is adequate even if beyond the standard volume. You only have to worry about service volume when flying direct (off route).
 
Jim- that calculation is built into the VOR type (high altitude, low attitude, and terminal). Also considered is the proximity of other VORs on the same frequency that may interfere with each other.

The service radius of HVOR decreases from 130 nautical miles to 100nm above 45,000 feet because of the possibility of picking up multiple VORs. An image depicting this service area for an HVOR is shown below. The various VORs also have differing power that affects the range as well ranging from 50W for a TVOR through 200W for a HVOR.

highAltitudeVOR.gif
 
As long as we're getting in to these details, we may as well also note that a great many VORs have unusable radials and different altitudes. These are sometimes listed in the A/FD, sometimes in the NOTAMs. These can bite you at bad times, like when you're counting on a given VOR to help keep you clear of a certain class B area...

(no, I kept clear, but it taught me a lesson)
 
Cap'n Jack said:
Jim- that calculation is built into the VOR type (high altitude, low attitude, and terminal). Also considered is the proximity of other VORs on the same frequency that may interfere with each other.

The service radius of HVOR decreases from 130 nautical miles to 100nm above 45,000 feet because of the possibility of picking up multiple VORs. An image depicting this service area for an HVOR is shown below. The various VORs also have differing power that affects the range as well ranging from 50W for a TVOR through 200W for a HVOR.

highAltitudeVOR.gif
Click to expand...

I respectfully beg to differ.

First of all, those of us in here rarely fly above 12.5, so the 40 mile ring from 1000 to 14,500 is just not true. Neglect all that stuff above 14.5.

Second of all, the theoretical range of a 1 watt transmitter on one end and a 1 microvolt receiver on the other end is something on the order of 1300 miles. Don't believe it? I've got a confirmation card from the Space Shuttle confirming contact with a 1 watt transmitter on my end and whatever they've got up there as a receiver.

Third, that 40 mile cylinder is really a cone that gets much bigger the higher you go. A 100 mile range at 10.5 is what most of us expect out in the west, where VORs are few and far between and interference on the same frequency is a minimum.

Jim
 
weirdjim said:
I respectfully beg to differ.

First of all, those of us in here rarely fly above 12.5, so the 40 mile ring from 1000 to 14,500 is just not true. Neglect all that stuff above 14.5.
Click to expand...
Fair enough- the people that do go above 14.5 would know this already.

weirdjim said:
Second of all, the theoretical range of a 1 watt transmitter on one end and a 1 microvolt receiver on the other end is something on the order of 1300 miles. Don't believe it? I've got a confirmation card from the Space Shuttle confirming contact with a 1 watt transmitter on my end and whatever they've got up there as a receiver.
Click to expand...
Look at the energy picked up by various radio telescopes. Although very powerful at the source, the distance (hundreds of light years) means not much power is actually detectable here. We understand radio can be picked up over long distances if not attenuated. Picking up something from space isn't the question here.

weirdjim said:
Third, that 40 mile cylinder is really a cone that gets much bigger the higher you go. A 100 mile range at 10.5 is what most of us expect out in the west, where VORs are few and far between and interference on the same frequency is a minimum.
Jim
Click to expand...
Off airways, I'll just go with the service area the FAA (or whoever defines such things) guarantees- as listed in the AF/D. I'll leave the QSL for when I'm not navigating.

The question wasn't "At what distance I could receive a VOR?" but rather "how can I tell at what distance a reliable signal can be acquired?"

I'm not Roncachamp, so I'll stop here...
 
OK, all good info even if it was more than i needed. I also tend to go overboard myself with information, so it is all welcome even if only as a curiosity. Now one other question: Are all VORs located on airport grounds classified "terminal", or should I still look these up on a case-by-case basis?
 
jasc15 said:
OK, all good info even if it was more than i needed. I also tend to go overboard myself with information, so it is all welcome even if only as a curiosity. Now one other question: Are all VORs located on airport grounds classified "terminal", or should I still look these up on a case-by-case basis?
Click to expand...

Case-by-case. For example, DBQ VORTAC is H-class, on the field at Dubuque Regional Airport. MSN VORTAC is L-class, on Truax Field.
 
Cap'n Jack said:
"how can I tell at what distance a reliable signal can be acquired?"
Click to expand...
The only thing you can know a priori about whether you can pick up the signal (other than on a published route or intersection, which are all flight-checked OK even if beyond the SSV) is to use the SSV from the AIM less any published additional restrictions in the AIM or NOTAMs. Once in the air, if you get a good ID, good TO/FROM, no red flag, and a stable needle, you are receiving the signal "suitable for navigation," and can use it, but beyond the SSV, that can vary from day to day due to a host of conditions ranging from atmospherics to trucks driving by the VOR station.
 
Ron Levy said:
The only thing you can know a priori about whether you can pick up the signal (other than on a published route or intersection, which are all flight-checked OK even if beyond the SSV) is to use the SSV from the AIM less any published additional restrictions in the AIM or NOTAMs. Once in the air, if you get a good ID, good TO/FROM, no red flag, and a stable needle, you are receiving the signal "suitable for navigation," and can use it, but beyond the SSV, that can vary from day to day due to a host of conditions ranging from atmospherics to trucks driving by the VOR station.
Click to expand...

Should be Airport/Facility Directory
 
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