We report the use of optical pulse shaping to convert single femtosecond pulses into lower-intensity pulse sequences for excitation of photoconductive dipole antennas, which results in the generation of bursts of tunable narrow-band free-space terahertz radiation. Our experiments demonstrate that the use of such pulse sequences can significantly enhance the spectral amplitude of the narrow-band terahertz radiation by avoiding the saturation effects that occur with single-pulse excitation. Our technique also provides the capability for terahertz wave-form shaping.