Why is HD 2 becoming such a secret? Seems station's web site no longer have the link or even acknowledge their HD2. Also like to know who came up with High Definition for radio? What does that mean?
Some stations are broadcasting a format on their HD2 and HD3 and in some cases, HD4 channels, that they would rather not have "compete" with their main Analog and HD1 channels. That might explain why the silence on that.
Additionally, if a station transmits an HD2 carrier, then the bandwidth of the HD1 carrier must be reduced, as the total maximum for FM "HD" is 96 kbps. There are more problems receiving the HD2 carriers further away from the transmitter site, as less power is allocated to HD2 than HD1. HD1, as many of us are well aware of, has it's own set of reliability of reception problems, often reception is less than reliable 10 to 20 miles away from the transmitter. Compare the reliable radius of an Analog signal, approximately 65 miles for Class B* and perhaps up to 100 miles for a Class C** station. So digital coverage does not even approach that of analog coverage. We have been seeing that happen on digital TV, with stations asking for power increases to regain lost coverage area.
*Class B 50kW ERP @ 150 meters antenna height (or equivalent) **Class C 100kW ERP @ 600 meters antenna height (or equivalent)
The acronym "HD" for Radio is supposed to mean Hybrid Digital
! (that is, Analog and Digital carriers are supposed
to coexist in the same channel channel space for a broadcast station. However, many of us know the digital carriers produce noise on an Analog RF carrier, and it's likely that the Analog signal also degrades the Digital signal as well - though to a lesser extent, relatively speaking)
I don't believe anyone in the industry is calling HD Radio, "High Definition", as it's NOT! Unfortunately, the highest bit rate currently for HD FM is 96 kbps, and for HD AM it's 32 kbps. We can do better with a smartphone...that's at least up to 128 kbps! And 128 k is not even considered "HD"...I believe many audio purists say nothing less than 256 kbps qualifies as High Definition, with CD's being 320 kbps.