Service Volumes of VOR's make no sense

On Wed, 11 May 2005 21:10:13 -0700, Antoñio
wrote:

I was at a CFI safety meeting today and the subject of VOR service
volumes came up. The AIM describes the Standard High Service Volume as
providing positive course guidance at varying distances depending on
your altitude--40nm at 1000ft., 100nm at 14,500ft, 130nm at 45,000ft, etc.

If the VOR is a "line of sight" signal device. How can there be varying
distances of service at varying altitudes? I mean, shouldn't I be able
to pick up a VOR radial from the moon as long as no obstructions intervene?

The way it was explained to me was that once you get above a certain
altitude you can start getting interference from other VORs with the
same frequency, so the 'valid' radius starts getting shorter again.

"Antoñio" wrote in message
...

I was at a CFI safety meeting today and the subject of VOR service volumes
came up. The AIM describes the Standard High Service Volume as providing
positive course guidance at varying distances depending on your
altitude--40nm at 1000ft., 100nm at 14,500ft, 130nm at 45,000ft, etc.

If the VOR is a "line of sight" signal device. How can there be varying
distances of service at varying altitudes? I mean, shouldn't I be able to
pick up a VOR radial from the moon as long as no obstructions intervene?


Yes, and every other VOR on that frequency as well. The altitude/distance
limits ensure you won't receive an unwanted VOR signal. Note that the
service volume decreases from 130 miles to 100 miles above FL 450.

Isn't that the reason certain airways have a MAA - Maximum Authorized
Altitude?

"Steven P. McNicoll" wrote in
nk.net:


"Antoñio" wrote in
message ...

I was at a CFI safety meeting today and the subject of VOR service
volumes came up. The AIM describes the Standard High Service Volume
as providing positive course guidance at varying distances depending
on your altitude--40nm at 1000ft., 100nm at 14,500ft, 130nm at
45,000ft, etc.

If the VOR is a "line of sight" signal device. How can there be
varying distances of service at varying altitudes? I mean, shouldn't
I be able to pick up a VOR radial from the moon as long as no
obstructions intervene?


Yes, and every other VOR on that frequency as well. The
altitude/distance limits ensure you won't receive an unwanted VOR
signal. Note that the service volume decreases from 130 miles to 100
miles above FL 450.

"Andrew Sarangan" wrote in message
1...

Isn't that the reason certain airways have a MAA - Maximum Authorized
Altitude?


Frequency overlap is probably the most common reason but they may also exist
due to conflicts with special use airspace.

Steven P. McNicoll wrote:

Yes, and every other VOR on that frequency as well. The altitude/distance
limits ensure you won't receive an unwanted VOR signal. Note that the
service volume decreases from 130 miles to 100 miles above FL 450.



Exactly! And that was the reason for my confusion and original question.

Antonio

The signal strength from a VOR decreases with distance. You are on a
straight line to the VOR from the moon but the signal strength would be too
low to create guidance.

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

"Steven P. McNicoll" wrote in message
nk.net...

"Antoñio" wrote in message
...

I was at a CFI safety meeting today and the subject of VOR service
volumes
came up. The AIM describes the Standard High Service Volume as providing
positive course guidance at varying distances depending on your
altitude--40nm at 1000ft., 100nm at 14,500ft, 130nm at 45,000ft, etc.

If the VOR is a "line of sight" signal device. How can there be varying
distances of service at varying altitudes? I mean, shouldn't I be able
to
pick up a VOR radial from the moon as long as no obstructions intervene?


Yes, and every other VOR on that frequency as well. The altitude/distance
limits ensure you won't receive an unwanted VOR signal. Note that the
service volume decreases from 130 miles to 100 miles above FL 450.

"Darrell S" wrote in message
news:4R4he.25286$tQ.4405@fed1read06...

The signal strength from a VOR decreases with distance. You are on a
straight line to the VOR from the moon but the signal strength would be
too low to create guidance.


I think he was speaking figuratively, aircraft do not operate very well
outside the atmosphere.

"Darrell S" wrote in message
news:4R4he.25286$tQ.4405@fed1read06...
The signal strength from a VOR decreases with distance. You are on a
straight line to the VOR from the moon but the signal strength would be
too
low to create guidance.

Signal is too weak to use with today's receivers, but a signal is never too
weak, with the right receiver. Look at the space robots; still in contact,
at the edge of the solar system. Amazing.
--
Jim in NC

On Fri, 13 May 2005 19:08:15 -0400, "Morgans"
wrote in ::

but a signal is never too weak, with the right receiver.

True, provided the random background noise doesn't significantly
exceed the signal strength of the source you want to receive.

On Wed, 11 May 2005 21:10:13 -0700, Antoñio
wrote:

I was at a CFI safety meeting today and the subject of VOR service
volumes came up. The AIM describes the Standard High Service Volume as
providing positive course guidance at varying distances depending on
your altitude--40nm at 1000ft., 100nm at 14,500ft, 130nm at 45,000ft, etc.

Hi...
To try to make a realllllly long explanation short....(er)

Those are the 'design' or 'advertised' service volumes. This is the
required minimum coverage they are flight checked for.

Will the FAA guarantee coverage outside of that? Nope.

Will you pick up a useable signal outside of that?
Possibly....maybe...depending on altitude/distance/terrain
But they don't guarantee xx nm at xxxx feet.

--Don Byrer


Don Byrer
Instrument Pilot Commercial/CFI Student
Electronics Technician, RADAR/Data/Comm @ CLE
Amateur Radio KJ5KB

"I have slipped the surly bonds of earth; now if I can just land without bending the gear..."