Echo box
As Echobox in the are radar measuring devices designated for measuring high frequency. Echo boxes are used in pulse radar devices.
High resistance measuring device
The high-resistance measuring device is a tunable parallel resonant circuit that is usually mounted near the antenna. If it is in resonance with the transmission pulse, this oscillating circuit continues to oscillate. A damped oscillation is formed , which "resonates" for a certain time. This reverberation lasts into the reception time. The longer it takes, the better the transmission power and receiver sensitivity can be assessed. The duration of the ringing can also be specified as a distance. “Reverberation up to 75 km” means that the energy emitted by the echo box only sinks below the receiver sensitivity of the radar device after 0.5 ms - that the display device is brightened up to 75 km during this time.
Low resistance measuring device
Another device, trivially referred to as an echo box, is a calibrated suction circuit which has the lowest possible ohmic resistance at the resonance frequency . In connection with a frequency-independent power meter, this measuring device can be used to determine the exact frequency of a transmitter.
With counting frequency meters , the measuring range of which extends into the working frequencies of radar devices, echo boxes have lost their importance as frequency measuring devices.