Radio Aids to Navigation: the Radio Range and Radio Compass

Periscope Films provides this vintage training film and the following commentary with callouts for specific aspects of radio navigation, including the Four Course Radio Range (Adcock Range), and both manual and automatic radio compasses (direction finders). 

Although modern GPS navigation makes these methods seem crude, the importance of radio aids to navigation for both commercial and military purposes was immense.

The Four Course Radio Range has long been obsolete and very little remains except for some LF beacons that still occupy the same frequency.   Only a few have survived semi-intact, including this one that used vertical towers at Ft. Shasta CA:

Another radio range that used horizontal wire antennas supported by wood poles is partially still standing at Whitmore, CA:

A number of good informational websites can be found online for those wishing to learn more about the low frequency range, but this video really shows it in operation during it's prime.    The last Low-frequency Range (LFR) instrument approach procedure in the U.S., at Elkins, West Virginia, was deleted on January 16, 1969. On August 25, 1960 there were 258 LFR's in the 50 states, down from a maximum of 440+ in the late 1940's.   The most that remains of this fascinating era of radio navigation are some concrete tower footings or perhaps an abandoned or repurposed generator building.

This Army Air Corps training film is part of a larger group of training films on aerial navigation. Produced in 1941, Aerial Navigation: Radio Aids gives an overview of how to use radio frequencies to determine an aircraft’s position. The film opens with a B-17 Flying Fortress flying through the clouds, then the film shows several radio towers. Footage shows the cockpit and instrument panel of an aircraft, presumably of the B-17. The film shows the Air Navigation Radio Aids handbook published by the Civil Aeronautics Administration (01:45). There is an aerial view of a radio range station. Graphics are used to show how radio fields are set up at a range station using radiators. A map shows radio range coverage in the U.S. (05:27). The film shows a radio tower and discusses the “cone of silence,” which is located directly above a radio tower (06:50). A pilot sits in the cockpit and adjusts knobs on his radio panel (07:29). Z-type markers are used at a radio range station (08:58). A marker beacon in the plane flashes when a plane flies over the Z-type marker (09:41). A fan marker can also be used as a position marker at a radio range system (10:05). The pilot watches the plane’s marker beacon signaling when it is in range of the fan marker. A pilot dials in his range receiver (12:29). The pilot looks at his radio facilities chart. A graphic is used to show how a pilot adjusts his course based on the signals he receives from a radio beam. The film uses basic animation over an aerial photograph to show how a plane can make minor adjustments while the pilot is trying to determine the correct course (18:00). A pilot adjusts the volume of his radio in the cockpit (18:40). A man in a range station transmits regular weather reports (22:31). The film shows the fifth radio tower of a range station that is for voice transmissions, primarily weather reports. The film then shows the radio compass on the instrument panel (23:29) and its antennae on the exterior of the plane. A man takes off the cover of a loop antennae on the top of an aircraft (24:40). A pilot plots his location on a chart (26:30). The film then shows the new automatic compass panel (26:47). A plane flies over a radio tower of a radio range station, concluding the film.