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The structure of systems for the automatic detection of radar echos in interference signals may be derived by the statistical decision theory if the statistical properties of echos and interference are known. The knowledge of the correlation function from fixed targets and weather echoes is of special interest. Photographic records in combination with an oscilloscope are feasible only for a low number of signals and were done for echoes from aircraft. For evaluation of the correlation function with sufficient accuracy nearly 10sdata have to be used. They have to be selected out of a quantity of about (3 ... 5).10sstored data. This large amount of data can only be handled with a computer. A special device (RADICORD) was developed to store the analog radar signal of a usual surveillance radar. The amplitude and phase components are sampled (1 MHz clock rate) and converted into digital words (8 bits). A buffer unit reduces the data rate and makes storage on tape possible. The recorded information is restricted to the signals of targets and small surrounding area by a variable gate. The evaluation is done with ALGOL or FORTRAN computer programs. The method of evaluation depends on the kind of target. Correlation functions and power spectral densities are calculated for two-dimensional targets as ground clutter and weather clutter. Mean values and probability densities of charac, teristic values are computed for single targets as aircraft, helicopters, and bird echos.