The 180º 13C pulse from the decoupler is usually calibrated from the 90º 13C decoupler pulse calibration test. Alternatively, it can also be measured from a variant of the classical four-pulse HMQC pulse train. Following the same procedure as described for 90º 13C decoupler pulse calibration test, change the pulse program to dec180 and reach the minimum signal intensity for the satelite lines by varying the p3 value. For a better solvent suppressed version, you can use the pulprog dec180pr. In this case you can define d1 and pl9: