It is a common belief, especially among those either jamming, using unlicensed radios or frequencies that were not allocated to them, that there is no way to locate them. It is further assumed that the FCC does not take the time to track down these offenders, which in many cases may be true. However, Radio Direction Finding has been around since the inception of radio. Early methods relied on the use of directional antennas and signal level meters to establish the bearing of the transmission source. By taking vectors from multiple locations on a map, the technique of triangulation could be used to determine the exact location. This method did take some time and skill to execute, but was indeed possible.
Before GPS technology, aircraft and ships had to rely on radios to determine their direction. The radios would be tuned to special radio transmitters or beacons, which could provide the bearings necessary for navigation. This was the primary way that aircraft and ships located their destinations prior to the invention of GPS. By using these methods, pilots and sailors could easily navigate to their intended destination. While the radios were less precise than GPS, they still provided sailors and pilots with reliable navigation and allowed them to travel safely and reliably.
Today there is more accurate and sophisticated equipment based on Doppler shift or time delays (radio waves travel at the speed of light). These methods allow for more precise direction finding, enabling operators to determine the precise location of a radio signal in real time. Radio direction finding is an invaluable tool in many industries, from tracking down stolen vehicles to locating missing persons.
While some effort is still required, the technology is available to radio technicians and amateur radio operators to track down rogue transmitters. Among amateur radio operators, tracking down these hidden transmitters can be an enjoyable pastime. However, although rogue transmitters may go unnoticed for some time, there is an accessible pool of people who are capable of locating and reporting the offending transmitter to the FCC. There may not be as many as actions as would be wished for, but the FCC does take enforcement actions which can be very expensive.
It is quite possible to find interference sources.