An apparatus for the detection of weak ionospheric echoes

An apparatus is described with which weak ionospheric echoes can be detected and their heights measured; it makes use of frequency modulation and coherent integration. With a transmitted power of 250 watts and an output bandwidth of 1 c/s the apparatus makes possible the detection of echoes corresponding to a reflection coefficient of 3×10¿5 (attenuation of 10 nepers). It is pointed out that the principle might be of use in the design of sensitive radar equipment.