FAA VOR radar site staying for now
As you drive southbound on SD-73 and approach the old "pipeline man camp," Looking east, you will see this round white building with a large white cone on top. This white tower is a VOR, which stands for Very High-Frequency Omnidirectional Radio Range tower. VOR stands for VHF Omnidirectional Range.
VOR is a low-power radio navigation system used in aviation to provide pilots with a reliable means of determining their position and navigating along a specific course. These towers are owned and operated by the Federal Aviation Administration FAA and many of these installations have been decommissioned as they are replaced with newer satellite-based navigational systems. The VOR sights that will remain, such as the one in Philip (for now), are part of the Minimum Operational Network (MON). However, more closures of VOR sights are slated through 2025. VOR towers that have already been decommissioned were in Winner, Huron, Buffalo, and Watertown thus far.
VOR stations transmit radio signals that aircraft can receive with VOR receivers. By comparing the signals received from multiple VOR stations, pilots can determine their radial distance and bearing from each station, allowing them to navigate accurately. VOR is widely used in aviation, especially for instrument flight and air navigation. VOR works by transmitting radio signals from ground-based VOR stations. These stations are typically located at airports or other strategic locations. The VOR station emits two movements: a reference signal and a variable signal.
Here is a brief explanation of this system and how it works. A reference signal is transmitted in all directions and is a fixed reference point. The variable signal is sent in a rotating pattern surrounding the station, creating a 360-degree circle of signals being transmitted. That is the reason for the cone shape. Initially, the inside of the cone tower used to spin. But due to maintenance issues, they upgraded the system with an electronically rotating signal instead. As the pilot flies "tracking inbound" (towards the VOR station), they are heading TO the station. Conversely, when the pilot is flying outbound, they are running away from the signal and will get a FROM indication on their instruments. In the image below, CDI stands for Course Deviation Indicator and tells the aircraft's lateral position in relation to the course. The track is the craft's actual direction traveled. Each Dot (actual dot on the instrument) represents two degrees of discrepancy from the course selected by the OBS (OBS Bearing Selector). The location of all VOR stations is plotted on an aeronautical map along with the name of the station and the frequency of the station, which an aircraft can listen to. Also, a Morris code identifier for the station allows navigation to that location.