A waveguide 200 for a leaky wave antenna 20 is described. The waveguide 200 comprises a male member 210 (210A-210T) and a corresponding female member 220 (220A-220T) arranged to receive the male member 210 (210A-210T) therein. The waveguide is arrangeable in a first configuration and a second configuration. The male member 210 (210A-210T) is received in the female member 220 (220A-220T) spaced apart therefrom in the first configuration and the second configuration. The first configuration defines a first effective delay line. The second configuration defines a second effective delay line. The first effective delay line is different from the second effective delay line. The leaky wave antenna 20 is also described.