From iBiquity Digital Corporation PowerPoint presentation made to senior FCC officials, October 3 and 4, 2001.
This is a graphical representaton of the bandwidth utilized by HD Radio stations.
Analog AM stations occupy 10 kilohertz (kHz) of bandwidth; analog FM stations occupy 200 kHz.
This iBiquity diagram clearly shows that hybrid and all-digital FM signals occupy approximately 400 kHz - double the spectrum of an analog signal.
On AM, the hybrid analog/digital mode occupies 30 kHz - three times the spectrum of an analog signal. iBiquity proposes to "shrink" all-digital AM signals to 20 kHz, which still represent twice the spread of analog bandwidth use.