A simple Fourier transform spectrometer was designed and constructed for the measurement of detectors,sources,passive devices and materials in the terahertz(THz) range.It can be operated at frequencies between 0.3 and 1.5 THz,using a 50-μm-thick Mylar-film beam splitter.The spectral range can be changed by altering the thickness of the beam splitter.The highest frequency resolution is 750 MHz.We studied the properties of heterodyne detectors including superconductor mixers and semiconductor harmonic mixers,direct detectors including an InSb semiconductor bolometer,superconducting tunnel junctions and the Golay cell,and sources including Gunn oscillators and a microwave source with its multipliers,as well as various materials and passive devices including Si wafers and metal mesh filters. A simple Fourier transform spectrometer was designed and constructed for the measurement of detectors, sources, passive devices and materials in the terahertz (THz) range. It can be operated at frequencies between 0.3 and 1.5 THz, using a 50-μm-thick Mylar- film beam splitter. The spectral range can be changed by altering the thickness of the beam splitter. The highest frequency resolution is 750 MHz. We studied the properties of heterodyne detectors including superconductor mixers and semiconductor harmonic mixers, direct detectors including an InSb semiconductor bolometer, superconducting tunnel junctions and the Golay cell, and sources including Gunn oscillators and a microwave source with its multipliers, as well as various materials and passive devices including Si wafers and metal mesh filters.