A double stay wire anchoring block for 1923 lattice masts 11 and 12 (anchors 11C and 12B as allocated by the Marconi Co.)  It is of a polygonal shape, measuring 4.48m x 0.955m x 3.27m x 0.955m x 3.93m and has two sloping faces into which a 18cm x 3.2cm (7 inch x 1 ¼ inch as built) steel strap, the main anchoring point for the mast guy wire, is embedded in the concrete base. On either side of the strap two, now cut loops were installed which are seen in Marconi archive photos to have been attachment points for what were probably temporary guy wires for construction. The upper surface of the anchor block slopes very slightly towards the centre and rear (north east).  At the western end, the anchor concrete is poured up against the natural rock rather than having a complete, constructed face. Copper screws are inserted on the upper face, which secured earth straps running to ground at the northeastern face.

Source: Rowlands, J., Marconi's Carnarvon Station 1912-1939: a journey into early commercial wireless in north Wales' Second Edition, 2023.

RCAHMW, 2023.