We describe a real-time, fast Fourier transform digital spectrometer, based on the new Sharp LH9124 chip. The system is fully programable, and in the present configuration it can measure the power spectrum of an incoming signal with a bandwidth of up to 20 MHz, a time resolution of 30 ms, a frequency resolution of up to 128 K channels, and a temporal duty cycle of 45% at 6 MHz bandwidth. An upgrade of the spectrometer is in progress, which will allow a duty cycle (efficiency) of 100% at 12 MHz bandwidth (single channel) or 6 MHz (dual channel). This new approach to the spectrum analysis will open new observational capabilities in radio astronomy and other fields.