The course gives an introduction to some of the principle techniques and instruments commonly used in atmospheric, ionospheric and magnetospheric research. The main emphasis is placed on the incoherent scatter radar technique (e.g. the EISCAT radar system), but auxiliary instruments such as lidars (ALOMAR system), magnetometers, riometers, optical equipment, specific satellite and rocket instrumentation may also be discussed. The auxiliary part of the course content is dynamic in order to reflect the interests of the participating students. The incoherent scatter technique covers about 70 percent of the course, and the content is focused on universal aspects of volume scattering, the scattering from density fluctuations in plasma, derivation of the power density spectrum and discussion of the retrieved ionospheric parameters. We proceed with considering the effects of measurement errors due to the random nature of the received signal. The first part of the course ends with radar fundamentals such as the radar equation for a diffuse target, the concept of a range-time diagram, pulse coding techniques and the effects of different modulation and detection schemes.