Locating a radio transmitter has a variety of uses, from finding that weird voice coming through your TV to just doing it for fun. You find the location through a process called triangulation, which at its most basic requires nothing more than a radio capable of receiving the transmission you wish to locate and a good ear. With practice the process becomes quick and easy, and you'll be tracking down all kinds of radio interference in no time.
Triangulation is the process of determining the location of a radio transmitter by taking readings at multiple locations and plotting the angle to the transmitter using signal strength as a guide. At a given location, the signal is strongest in one direction, allowing you to draw an imaginary line in the direction of that signal. You then move to another location and repeat the process. Where the imaginary lines converge is where the transmitter is located.
Basic Steps and Equipment
To locate a radio via triangulation, you need a receiver capable of picking up the transmission or broadcast you wish to track down. This can be a scanner, or even an AM or FM radio if you are trying to find a broadcast transmitter. Start by taking your first signal strength measurement. Note that while you can use the signal strength meter if your receiver has one, judging signal strength by ear works just as well. Note the direction in which the signal appears to be loudest, and then move to another location and repeat the process. At first the distance between measurements may need to be several hundred yards or even miles, depending on the transmitter you are finding, but you can narrow down the distance between measurement points as you get closer to the source.
Advanced Techniques and Equipment
When nearing the source of the transmissions or attempting to triangulate very strong signals, it can be difficult to determine in what direction the signal is strongest. One technique is to use your body as a shield. Hold the receiver close to your chest, and instead listen for when the signal fades the most, which indicates that rhe transmitter is in the opposite direction. You can also remove the antenna and use a paper clip to attenuate strong signals, or even purchase or build an attenuator. Using a small, hand-held directional antenna can also make triangulation easier, as a directional antenna is very effective at rejecting signals it is not directly pointed towards, due to their high front-to-back ratios.
Don't trespass on private property while attempting to triangulate. If you absolutely need to in order to continue your location, contact the property owner first. Don't touch any broadcast radio transmitting equipment, as some stations use upwards of 50,000 watts in their transmitters -- more than enough to cause a serious RF burn. Ensure you are prepared for the weather and environment you will be working in. Wear appropriate shoes and clothing, and stay hydrated in hot weather.