Between two FM stations there must be a considerable gap. In other, more technical words, centre-to-centre spacing of 800 kHz is required between two analogue FM transmitters (i.e., 600 kHz frequency gap). But a DRM digital transmitter can be installed at a spacing of only a 50 kHz frequency gap from an analogue FM transmission and/or another digital transmitter. Thus, DRM digital permits the operation of many more FM-band digital radio services, which in any case would be required particularly in major cities where the available spectrum is limited.