The most accurate full two-port calibration of a VNA Vector Network Analyzer requires a Direct or Zero-Length Through connection. However, it is not uncommon at all to have one or two cables and a DUT Device Under Test with incompatible con-nectors, either of different type or of the same type/sex, which enforce then the use of some kind of barrel or adapter. Thus, in this paper, we study these cases of Indirect or Non-Zero Length Through, we estimate the effects of such connections on the

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... rement uncertainty by using our theory of Differential Error Regions and Intervals DERs/DEIs, and we evaluate our resulting method by applying it in practice to a built two-port network, which was measured against frequency with a SLOT calibrated VNA extended by two lengthy cables.