Gain, differential gain and differential phase parameters as a function of time, as determined from the METM analyses of 1.4 GHz NUPPI data on PSR J1136+1551. The best-fit parameters displayed as blue dots are those for the 64th 4 MHz channel recorded by NUPPI, which has a central frequency of 1482 MHz. The solid vertical lines indicate PSR J0953+0755 observation epochs. The dashed vertical lines delimit intervals in which the instrumental response of the NRT is consistent across the bandwidth, between the epochs (see Sect. 3 for details).