Here is What You Should Know about Radio Direction Finder

Direction finder or radio detection finder combined with radio receiver and antenna system helps in finding the source direction of a radio signal. A DF is used in aircraft or a ship as a navigational aid. This is attained by ascertaining the direction of two transmitters whose locations are known. When the directions from each transmitter are plotted on a map, then the intersection of the two plotted lines provides the location of the aircraft or ship that is carrying the DF. This technique that uses the directions emitted by two or more transmitters is referred to as triangulation.

Due to its early use, the radio direction finder was also referred to as a radio compass. It is used as a navigational aid that is replaced by modern navigational equipment like GPS is the most famous as it is accurate, cost efficient and easy to use.

DF also comes in handy with military applications to seek hostile transmitters. It was helpful in WWII when the UK and the US used it for combating the German submarines in the North Atlantic. These submarines caused heavy losses of Allied shipping in the war’s early years. When a German Submarine found an Allied convoy, they radioed the location of the convoy to its HQ so that other submarines can be notified and then join the attacked. Began in the late 1941, DFs were equipped on convoy escort ships and at shore stations. As the submarine communications were at high frequency, or shortwaves, these devices were referred to as HF/DF or Huff Duff. Its usage gave must credit along with microwave radar and Ultra to defeat the German submarine threat.

The Huff Duff communication served long distances through refraction of the electromagnetic waves by the ionosphere. The huge ground-based Huff Duff stations made most of this to seek the transmitters to up to 5000 km. This was mainly used for strategic intelligence collection and transmitter location. The former entails large array of vertical dipoles arranged in a circle up to 250 m. In many cases, two or more concentric circular arrays are used to raise the bandwidth over where the system is run.