The bandwidth demand for data transmission on copper cables increases more and more. For the characterisation of such cables up to GHz frequencies it is advisable to use a vector network analyzer (VNA). However, the effort for its calibration can be considerable, since a star-quad cable consists of two twisted-pairs, which results in 128 calibration coefficients to be determined. It has previously been shown [1] how to reduce the number of calibration coefficients significantly, by exploiting symmetry properties within a mixed-mode description of the measurement setup. As a part of that solution, four leaky 4-port error-networks must be calibrated. For this purpose, the present paper presents a novel combination of calibration standards to calibrate two 15-term error-networks in one step, the so called 31-term error-model. This procedure applies two network standards “N1” and “N2” to connect the two 15-term error-networks, a third network “N3” to connect both ports at the leaky error-networks and an asymmetric reflection standard “R”. The paper adresses the problem of MATCH-standards on non-metrology interfaces. They set the reference impedance, but have not a constant reflection for a bandwith of several GHz.