HD Radio is a bridging technology designed to replace traditional FM transmission. Instead of radio waves, a digital signal is transmitted which is received by HD Radio receivers and converted into sound. Many HD Radio radios are also capable of FM reception in addition to the HD Radio standard. These devices are also referred to as hybrid radios. The variety of stations for HD Radio is somewhat greater than via FM.
FM frequencies on which the stations are transmitted must be far enough apart from each other. And since only a limited frequency spectrum is available, the number of potential stations in any given broadcasting area is limited.
The transmission of HD Radio signals has far fewer restrictions here, which is why more stations can be broadcast in a HD Radio transmission area. The choice is even greater with web radios and internet radios, as each radio station here has unique stream URLs and there can be no overlaps.