We studied the waveguiding properties of a photonic quasicrystal based on an octagonal tiling. The structure exhibits intrinsic localisation in the band gap region, that can be exploited to manipulate the signal transmission through a linear defect. The electromagnetic characteristics are first numerically analysed using a full wave simulation and then experimentally verified by measurements carried out in the X-band microwave region. Possible photonic applications include tunable notch filters having large attenuation.