Left panel: 323 MHz GMRT low–resolution (21.1′′× 17.2′′, p.a. 28.8°) image of the same 19′× 19′ region around the cluster M 0520 (same as in Fig. 1); black contours are spaced by a factor of two and start at ±3σ_{323 MHz} = 0.82 mJy/b. (Negative contours are dashed.) To highlight the position of discrete compact radio sources in the field, contours from the full–resolution image (see Fig. 1) are over-plotted in red, starting from ± 6σ = 0.66 mJy/b. Dotted ellipses mark the location of diffuse emission, labelled D1 to D4. Right panel: VLA 1.4 GHz contours (in blue) of an image obtained from re-processed NVSS data (45.8′′× 29.9′′, p.a. −70.0°); contours start at ± 2σ_{1400 MHz} = 0.5 mJy/b and are spaced by a factor of 2 (blue dashed contours are negative). The contours are overlaid on a 323 MHz GMRT image of similar resolution (41.5′′× 33.5′′, p.a. 21.3°), shown in grey scale. (The grey dashed contour corresponds to 3σ_{323 MHz} = 1.65 mJy/b).