Can someone explain FM HD? For example, I have the same number (97.1) which carries two HD channels under that number. I cannot "dial" in the HD2 channel. I have to go to the "Local Stations" settings to find the HD2 (will show 97.1 HD1 and 97.1 HD2), although as I said, the HD2 will come and go.
"HD" is a marketing term which essentially tries to connect HDTV with its digital radio counterpart. The term is meaningless but is used by iBiquity (the developer of digital radio) as a marketing tool.
The proper term for digital radio is IBOC (In Band On Carrier). A digital signal is transmitted alongside the base signal (either FM or AM). FM works pretty well but IBOC puts a lot of interference out on the sidebands (the hiss I stated earlier). If you are hearing a hiss on your AM analog signal it is because of an adjacent digital signal and there is nothing you can do to eliminate it. If the interfering station unplugs its digital exciter the hiss will stop - so it can come and go.
Just like digital signals on TV, the range of a digital radio signal is much lower than a straight analog signal on the same frequency. Digital signals, both AM and FM, are also affected much more by topography (buildings, hills, tunnels etc.) than are analog signals - hence the reason that digital signals tend to drop out from time to time.
Most digital-capable radios are designed to fall back to the analog signal when the digital signal gets too weak. Since the two signals are generally not simulcast it seems to the listener that the radio is switching stations (which, in effect, is what it is doing) and it can become very annoying. Again, nothing you can do except turn off HD if the radio gives you that option.
With the Genny's Lexicon system, once you dial in an HD2 signal, you can store it just like any other station. Tuning a digital signal in the first time requires you to tune to the analog frequency then, once you see the "HD" symbol in the upper right corner of the screen, you depress the DIS knob and the radio will bring up the HD2 signal.
The iBiquity system has many severe inherent design problems and that is the prime reason why digital radio has not caught on. It was supposed to bring increased fidelity and more services to the FM and AM bands but the necessity of buying a new radio has limited its rollout almost exclusively to new car dashboards - where the mobile shortcomings are the worst.
If I didn't answer your question here please give me some additional detail and I will try again. I tried to keep my post very untechnical since most people don't understand digital radio.