This report documents work on the calibration of a logarithmic detector used in a measurement radar at FOI test site, Lilla Gåra, and on the calibration and characterisation of the optolinks and other external components used e.g. for bistatic measurements. This provides supplementary data for use in testing object-free radar cross section calibration reported elsewhere. The results include the mean detector sensitivity, the frequency response of the measurement system, correction and sensitivity curves for the detector, a correction curve for the external components used and information on the dynamic range of the measurement system but also the calibration methods used for the gathering and extraction of this information. The sensitivity of the detector was found to be close to that specified on delivery, i.e. the detector was found to be stable. The non-linear corrections found are typical for this kind of detector. Application of the corrections are expected to yield significant but not drastic improvements. The external components only show slight non-linearities, but do to some extent limit the dynamic range. The principle used for calibration is to measure the response of the detector at many different attenuations and radar frequencies. The attenuation is varied using a digitally stepped attenuator. Since the frequency response is initially unknown this means that the input signal level is only known relative to the other attenuation levels at the same radar frequency. By selecting a certain, nearly linear, section of the detector response curve for each frequency the system response at this frequency can be estimated from a linear fit. The slope is the mean detector sensitivity and the intercept at zero attenuation represents the system response at that radar frequency. The fit provides an estimate of the detector input level on a scale that, though still relative, is common for all radar frequencies. Differences between measured responses and linear fits provide correction estimates and form the basis for the correction curve reported.