Harmon Technologies, Inc.

Automatic Direction Finder

The automatic direction finder can receive low frequency navigation beacons or AM broadcast stations (like WRKO).  When a station is being received, the yellow needle always points to the station.  This can be used to fly to or from the station on a desired course and also to remain oriented while using other techniques (usually VOR) as the primary means of navigation.

Most instrument landing system approaches (such as found at Logan, Hanscom, and Lawrence) have a beacon exactly 5 miles from the end of the runway.  This provides guidance when setting up for the approach and confirms the point at which the final approach is started.

ADF receivers are old technology but are still valuable as an additional resource.  In remote areas, they may be the only type of navigation available when performing an instrument approach to smaller airports.

Copyright © 2004 Harmon Technologies, Inc.