Patrick Martin wrote:
If a station wants to turn off the analog AM, then why not just put a tower on a mountain and run FM or a small amount of FM repeaters or some form of satellite radio? It would be a lot less than running high power AM period. AM IBOC does not have a lot of coverage and in the mountainous areas of Alaska lead in a big issue, that the stations don'talways get out well on AM.
As I understand it, it's a question of making use of existing resources and keeping the engineering as uncomplicated as possible under the difficult circumstances many of these stations face. Most of the bush AMs (I believe KBRW is a notable exception) operate studios and transmitters at a common site. No studio-transmitter links to go down, no remote transmitter sites to try to get to when something fails, no big networks of low-power repeaters that have to be maintained. Just a tower that's already built and paid for, right there on site. Remember, at a lot of these stations there is no resident engineer - if something breaks, someone has to be flown in at great expense. So there's a huge priority put on simplicity, and it's hard to get much simpler than a non-directional AM that's right there next to the studio.
The question of coverage is still an open one - we simply don't have any field experience yet to say how robust the digital signal would be if it were on-channel, digital-only, rather than the low-power sidebands in adjacent channels in the current hybrid system.
Satellite radio is challenging in Alaska, of course, because the geosynchronous birds are way down there at the horizon, and the low-orbit Sirius birds don't see that far north, either.
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