The development of effective techniques for guiding pulsed terahertz radiation is essential for the continued development of terahertz spectroscopy and imaging applications based on the technique of time-domain spectroscopy. Terahertz surface plasmon polaritons (SPPs) can be excited and guided on cylindrical metal wires with low loss and dispersion. This propagating surface wave, known as a Sommerfeld wave, possesses radial polarization, which is not well matched with conventional sources of pulsed terahertz radiation. A photoconductive terahertz antenna with radial symmetry produces radiation that more efficiently couples to the wire waveguide. At the end of the wire, terahertz SPPs emit radiation into free-space that exhibits frequency-dependent diffraction.