Observed lines of HC₇NH⁺ towards TMC-1 in the K/Ka band. The abscissa is the LSR velocity in km s⁻¹. The ordinate is the antenna temperature in millikelvin. The red line is the computed theoretical spectrum using the column density and rotational temperature derived by Cabezas et al. (2022b) and adopting a source diameter of 90″. The two spectra marked in green as RFI correspond to frequencies severely affected by RFI. Note the broad spectral features due to RFI present in the J = 18–17 line.