How Do RF Direction Finders Work?

To understand how RF direction finders work, it helps to understand how radio works. At its most basic fundamental element, electricity has to do with currents. AC (alternating current) and DC (direct current) currents that flow back and forth, measured in cycles per second, or more commonly known as Hz. Radio waves are measured in kHz, MHz and GHz. What radio is essentially is when the back and forth goes so fast that it jumps off the wire. The lower the frequency of the current, the longer the radio wave is, and inversely, the higher the frequency the shorter the wave. When the radio waves leave the wire, certain antennas can mold how they leave. Similarly, receiving antennas are custom made to receive certain frequencies and interpret them.

An RF direction finder is made to receive radio transmissions and determine the direction of the transmitter from data received by the antennae. These can be modified to many different radio frequency bandwidths and is applicable in land, sea and air situations. This can be incorporated for homeland security, aeronautical and marine navigation, the military, RF tagging systems such as animal tracking, and as beacon homing devices for search and rescue operations, and other emergency services. Some of the older RF direction finders date back to WWII, and were used primarily to locate enemies.

RF direction finding works in two processes: 1) Receiving and characterizing the signal, by determining the signal strength (closer is going to be stronger), the direction the signal came from, and the time of arrival. 2) Processing the data, and based on the information received, calculate the location of the signal

There do exist radio direction finding (RDF) networks, which as you can imagine, make signal finding much easier and more accurate than having just one finder. There are many benefits to having system-level locating abilities and centralized processing, and having all of the networks processing together from multiple receiving sites. An example of this is the Coast Guard Rescue network (the upgraded National Response and Distress System), which monitors the emergency channels for the marines, and locates distress calls so that response teams can locate the distress site.