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From: alkire@hplabsb.UUCP
Newsgroups: net.aviation
Subject: Need technical info for VOR
Message-ID: <2965@hplabsb.UUCP>
Date: Thu, 6-Jun-85 15:28:29 EDT
Article-I.D.: hplabsb.2965
Posted: Thu Jun  6 15:28:29 1985
Date-Received: Sat, 8-Jun-85 04:03:37 EDT
Organization: Hewlett Packard Labs, Palo Alto CA
Lines: 29

**

In my ground school class the other night, we talked about radio navigation,
specifically VOR navigation. I wanted to know more about the technical
specifics about how VOR works; however, my instructor really only knew how
to use it. Her description of how it worked seemed over-simplified and I
think there would be better ways of accomplishing the same results. 

What I got from her was: there is first an omnidirectional signal which is
broadcast and then a sweep of 360 degrees through 360 seperate directional
antennas.  The VOR receiver finds the one degree of sweep (a radial) with
the highest signal level from the VOR transmitter. It determines the angle
of that radial with respect to magnetic north by the phase relationship
between the omnidirectional signal and the radial. 

The 360 seperate antennas doesn't seem like the most efficient way of
sweeping 360 degrees. What I would like to find out is what sort of antenna
arrangement VOR uses and what are the characteristics of the omnidirectional
and radial signals i.e. What sort of modulation is used? AM? CW? FM? How
often is the sweep? How long is the omnidirectional signal or is it
continuous? What is the timing like between the omnidirectional signal and
the radial?

This doesn't have much to do with VOR navigation but it has my curiosity up
and I would appreciate any input on how VOR works technically. 

Thank You,

Bob Alkire @ hplabsb