Ionosonde is the generic name given to ionospheric sounders that uses basic radar techniques to detect the electron density of ionospheric plasma as a function of height. The equipment transmits electromagnetic energy pulses scanning the transmitted frequency from 1 MHz to as high as 40 MHz, in steps of 50 or 100 kHz. By measuring the time elapsed between the transmitted and the reflected signal, a vertical transmission ionosonde provides the electron density profile as a function of (virtual) height. The digital ionosonde also have the capability to measure the phase of the signal and its Doppler shift, allowing thus to obtain information about the dynamics of the reflecting ionospheric region. Digisondes are digital ionosondes with high capability to process the data immediately after its acquisition. This capability allows the use of the Digisonde data in program that requires ionospheric information in real time, such as the Space Weather forecasting.

The integrated Digisonde system consists of transmitter, an antenna switch, internal computers, peripherals and transmitting and receiving antennas. The electromagnetic signal is transmitted vertically to the ionosphere, with peak power of about 10 kW (for Digisonde DGS256) and of the order of 300 W (for models DPS and DPS-4-4D), by a Delta transmitting antenna with resistive load of 600 ohms. The reflected signal is received by a set of receiving antennas (4 or 7, depending on the adopted configuration).