Broad-band spectra for Aql X-1 for obs 1–3. The arrows represent 3 σ upper limits. Obs 1, 2a, 2b and 3 are shown in black in the upper-left, upper-right, lower-left and lower-right panels, respectively. For obs 3 we show two possible fits for the first slope: considering only the ATCA points and considering the ATCA points together with the ALMA points. The jet frequency break could be anywhere between ~30 GHz and 100 GHz depending on the solution taken. The jet break frequency evolves from ~100 GHz in obs 1, to ≲5 GHz in obs 2a and 2b and back to 30–100 GHz in obs 3.