Left – GMRT  153 MHz full-resolution image of A 697. Contours are spaced by a factor of two, starting from ±3σ_153  MHz =  ±2.4 mJy/b. The restoring beam is 26.2′′ × 20.8′′, PA − 89.5°. Crosses and labels mark the position of the point sources detected and optically identified at 325 MHz (M10). Right – GMRT  153 MHz low-resolution contours of the central radio halo in A 697, starting at ±3σ_153  MHz =  ±3.6 mJy/b and spaced by a factor of two. The resolution is 48.4′′ × 44.4′′, PA 3.5°. Contours are overlaid on the 325 MHz image (shown in greyscale, lowest level corresponding to 3σ_325  MHz), at a resolution of 46.8′′ × 41.4′′, PA 79.7° (M10).