Monitoring station receives and measures signals from radio transmitters. These signals come from such sources as AM and FM radio stations, television stations, radios in airplanes and ships, cellular telephone systems, satellites, and amateur radios. Some countries use monitoring stations as “listening posts” to obtain information from other countries.
In the United States, the Federal Communications Commission (FCC) operates 13 monitoring stations. A Canadian government department called Industry Canada operates 10 stations. Both government agencies issue transmitter licenses and enforce operating regulations determined by national and international laws. Monitoring stations measure radio transmissions often to make certain the stations are operating under these regulations and the terms of their licenses.
The United States and Canada also maintain many mobile monitoring vehicles. They are especially useful for measuring signals from limited-range, personal communication systems, such as cellular phone towers. Long-range direction finders, which are not mobile, help locate sources of radio interference, unauthorized transmitters, and aircraft and ships in distress. Modern technology enables nearly anyone to construct a personal monitoring station at reasonable cost.
