Radio Direction Finders

Ray Jefferson 6150 Automatic Radio Direction Finder (ADF)

 Radio Direction Finders. Il radiogoniometro è un ricevitore radio dedicato al rilevamento della direzione di provenienza delle trasmissioni che riceve, grazie all'uso di antenne radio direzionali, cioè dotate di una direzione di ricezione privilegiata, attraverso il rilevamento della posizione dei Radiofari.

I always had a certain fascination for the marine radio direction finders. It is a technology which had a window of usefulness, from the late 1920's until the advent and proliferation of GPS in the 1980's and 1990's gradually made them obsolete. By the year 2000 the last marine radio beacons were decommissioned, and the radio direction finder became a piece of maritime electronic history.

The only operating radio beacons are the ones still working out of airports. These will be phased out by about 2015, so enjoy them while they last. I am still able to clearly receive about 6 aero beacons from my home in Putnam County, NY, about 50 miles above NYC. After they are gone, it's AM Broadcast or nothing. There is a very concise list of them here. 

                 

http://www.dxinfocentre.com/ndb.htm

There are a few manufacturers of RDF's today. Some are used as a hobby/sport, known as "Fox Hunting". Others are used in "man overboard" systems, where crew carry small transmitters on their person. Vecta makes such a unit today. But here is one which I find interesting, the Vector Finder, by National RF. It can be purchased in different frequency ranges, including the old marine radio beacon band!  Below are some of the RDF's from my collection, grouped by major type. Some images are linked to a larger view.

http://www.angelfire.com/space/proto57/rdf.html

https://en.wikipedia.org/wiki/Radio_direction_finder

https://it.wikipedia.org/wiki/Radiogoniometro

Modellino di Radiofaro, nominativo "I - TRP ", in polistirolo costruito da Marco Cannamela