SEAMCAT allows you to define the spectrum as part of a spectrum range which can be strictly above or below the centre offset as shown in Figure 457.
Figure 457: Portion of spectrum mask definition (i.e. excluding the center offset)
This flexibility creates a restriction in the ACLR display. It is because the ACLR display algorithm is normalized to the in-band power. Therefore, in order to generate the ACLR display it is necessary to have the spectrum mask being defined within the range of the system emission bandwidth (centered to the zero offset).
By default, in the case where a user would set the mask so that the ACLR would fail to compute, SEAMCAT will automatically disable the ACLR display functionality as shown in Figure 458.
Figure 458: ACLR display functionality disabled due to the specific definition of the spectrum