Marine VHF Radio Direction Finders

By: Jed Tumlinson


A radio directional finder is also called a RDF and it is a device that is used to find the direction of the radio source. Marine VHF radio direction finders are commonly used to track navigation among ships and aircraft.

Radio are able to travel quite a distance which is why it�s the main navigation equipment for ships and aircraft which can both be found some distance from land.

A radio direction finder works by pointing a directional antenna in many directions and then listening to see which direction the signal from a recognized point comes through the strongest.

During the 1930�s and 1940�s this was a very popular system used during WW II. In fact the Japanese used RDF�s to hone in on Hawaii.

Today the process of finding the signal is usually automated called ADF. The automated system listens for a peak signal that repeats itself consistently.

During navigation the signals are in the form of a radio beacon with the signal being a basic AM broadcast of a Morse code. The RDF is able to tune in and see if the beacon is on the air.

It was once the primary form of airport navigation. They would string beacons together from one airport to another. By the 1950s the process of replacing with the VOR system had begun.

Today they are also obsolete on the water having been replaced by GPS which is not only more accurate it is a lot easier to use too. And by 2010 the ADF systems will be all shut off so even if you are still using them you�ll need to make the switch but until then you can use the ADF system to plot your position.

Most people have already made the move over to GPS which has become extremely affordable. In fact it�s probably more affordable than investing in a RDF system.

You can certainly find either RDF equipment or GPS online but we�d recommend you forget all about marine VHF radio direction finders and move into the 21st century. So what are you waiting for?


Jed has been working for leading leading retailers of marine electronics with over 10 years of experience in the maritime industry. Come to www.marine-electronics-now.com to get free advice on different range of marine electronics