One of the major challenges in the development of wearable antennas is to design an antenna that can at the same time satisfy technical requirements and be aesthetically acceptable and suitable for clothing applications. Slotted waveguide antennas made of conductive textiles meet all the demands for integration into clothing. However, the transition from a classic coaxial line into a waveguide remains an open problem and the aim of this paper is to consider and experimentally characterize different possibilities for making this transition.