¯ History of RDF    For over 80 years people have been engaged in developing equipment to locate the source of radio signals. Whether to save lives or destroy them the goal has been the same, to find the quickest and most accurate way of pinpointing the transmitter.     Radio Direction Finding (RDF), was anticipated by Marconi and Hertz as early as 1900. They demonstrated directional aerials and how they could be used to 'focus' a radio signal in a particular direction. (Equally of course, they could be used to reject signals from all but one direction). By 1912 Marconi had demonstrated a ship mounted system which could take bearings from land based transmitters. He obtained a patent for this equipment, which enabled the ships position to be calculated by triangulation. World War 1 saw the development of RDF for military use. The Navy were quick to capitalise on the advantage this gave them, locating enemy ships by listening to their 'radio traffic'. RDF played a decisive role in the location and destruction of the German High Seas Fleet at Jutland, RDF was now seen as a very useful tool. Development continued after the war and got it's next boost with the outbreak of World War II. There were more sophisticated DF systems to be had due to the developments in the miniaturisation of electronic components. DF loops could now be found fitted to aircraft. Destroyers could locate submarines as they surfaced to make clandestine transmissions. Bombers were able to fly along narrow beams of radio waves, which mysteriously guided them to their targets. And there was a new hero, Watson-Watt and his brilliant secret invention…. RADAR! Today, highly sophisticated RDF techniques are used to track the frequency hopping transmissions used in modern military communications. Whilst highly technical and ingenious, the basic principle is the same, capturing the angle of the transmission with respect to the aerial and equipment. 'Direction finding for fun' seemed to get started around the 1950's. Radio Amateurs were the culprits, modifying equipment and experimenting with different aerial arrangements. Family motor cars were more affordable and could be fitted with a car radio. These radios were easy to re-tune to operate in the 160 metre amateur band, and so by the efforts of these enterprising individuals ARDF was born. Today there is still Radio Fox Hunting activity on 160m (top-band), but there is also a great deal of fun to be had using 2 metres (145MHz). It is this system that is used on the Nottingham foxhunt evenings, and it 2 metre equipment and hunting that is described within these web-pages. copyright © silent design associates. 2001. all rights reserved.