Radar - Can you fly an aircraft without being detected in Radar?

Radar - Can you fly an aircraft without being detected in Radar?

Radar, or the Radio Detection and Ranging, is a detection technique that employs radio waves to discover the position or speed of a faraway object. The technology is being applied around the globe in the detection of aircrafts, ships, missiles etc. The system is built with a transmitter that emits the radio waves, an antenna that can transmit and receive the waves, and a receiver that has a processor to evaluate and obtain the properties of the object under inspection. Radio waves are continuously emitted from the transmitter. The waves that are reflected off the object are received by the receiver. The processor uses the data to evaluate the object’s position and speed.  

There is a coverage area for the radar and it depends on the terrain and the distance from the site. Tall buildings or mountains can block and reflect back the radio waves to the radar. This is called clutter. Thus in such terrain, the lower limit of the altitude above which the radar is fully functional, will be high. This altitude marks the beginning of the radar horizon, above which clutter will be ineffective. Thus, if you fly below a certain height, you will not be detected by the radar, or in other words, it is possible to fly under the radar. This is a practice followed by military aircrafts while attacking the enemy.  

Another technology used to avoid being detected is found in a stealth aircraft. It is home to a number of devices that reduces or limits the refection of radio waves, light waves, sound waves etc. This technology is called the stealth technology.