Tot left: GMRT 325 MHz map. Contour levels are drawn as in Fig. 1. Top right: VLA 1425 MHz map. Contour levels are drawn as in Fig. 1. Bottom left: power-law spectral index fit between 325, 610, and 1425 MHz. Contours are from the 1.4 GHz VLA image and drawn as in Fig. 2 (left panel). The resolution is 13.0″ × 12.4″. Bottom right: optical WHT color image for Abell 2048. GMRT 610 MHz contours are overlaid in yellow. The beam size is 7.6″ × 5.4″. Contour levels are drawn as in Fig. 5.