A line length estimate (electrical delay or free space equivalent length) is needed to help with root choice but this is not a critical parameter. Typically, one needs only be within a half-wavelength of the correct length at the maximum desired calibration frequency.

If the match of the reciprocal network is worse than -8 dB or the loss exceeds ~20 dB, the reciprocal treatment will start to degrade but a calibration will be possible. Since such a network is at the limits of de-embedding capability, there are few choices except to consider 1p-2p processing with scalar de-embedding.