Before the radar, how did people detect planes?

Today, it is easier to detect the movement of aircraft thanks to the help of radar systems. However, before the radar technology, how do people detect the movement of aircraft? By using sonar techniques with reflective mirrors or recording trumpets .

How the ancient people discovered aircraft without radar system

The recording horn looks like an extended pair of ears, designed in different shapes but with the same operating principle. This device uses antennas shaped like horn speakers so it is called a trumpet. These trumpets receive sound waves that travel through the air with a frequency that the human ear is not aware of.

The received sound waves pass through an audio amplifier to the frequency that the human ear can hear. The operators of this audio locator will analyze the sounds they hear and determine if the subject is moving to an airplane or vehicle. Thanks to the use of these sound locators, one can detect the movement of aircraft or vehicles at a certain distance.

The machine locates Czech 2 stereos audio in 1920.

German sound locator in 1940, this machine came closer to radar technology.

The British 4-pipe sound locator was used in 1938.

Meanwhile, the reflective mirror is a mystery like ordinary mirrors but instead of reflecting light, it is used to reflect sound, the idea of ​​which is thought by Dr. William Sansome Tucker. These mirrors are made from concrete and placed in the fields along the English coast during World War II, they are designed in a parabola shape and turn a concave face in the direction of the enemy plane to detect engine noise. remote aircraft. Typically, reflective mirrors are built in clusters of 3 with a height of 5m and a length of 70m, these mirrors are placed so that they will collect reflected sound at a point, where there are receivers and a The crew will measure the results, from which they calculate the distance of the machine compared to the air defense.

However, after the radar system developed completely with the speed of the aircraft getting faster and faster, these sonar systems were no longer effective in real combat, typically the German military incident. Using the V2 rocket to attack London has made the reflective mirrors only as useless concrete blocks because the rocket's speed far surpasses what humans knew at the time.