Left: spectra of the giant radio haloes in the GMRT Radio Halo Survey. The 325 MHz data points are reported in Table 4. The remaining data are taken from: A 697 Macario et al. (2010) and van Weeren et al. (2011a); A 521 Brunetti et al. (2008); RXCJ 2003.5–2323 Giacintucci et al. (2009). For A 1300 see Sect. 3.2.1; for A 1758N see Sect. 3.1.2; for A 2744 see Sect. 3.2.2. Right: spectra of relics from the GMRT radio Halo survey. The 325 MHz data points are reported in Table 4. The remaining data are taken from: A 521 G08; A 781 Venturi et al. (2011a); A 1300 R99; A 2744 see Sect. 3.2.2. In both panels the lines are drawn to help the visual inspection and are not the best fit power law.