[BC] Digital coverage

[gRAdy Moates]

>This probably doesn't bode too well for a lot of class A FMs out in 
>"B" country, particularly along the east coast.

    My feelings, exactly.  Ibiquity HD seems to work OK with full B's 
and C's, simly because the allocation system we use doesn't allow as 
many, small first- and second-adjacent interloper signals that are 
close-in to the primary service area of a station.  The smaller the 
footprint of a station, the more 'edge problems' it will have.

>I wonder if the situation would improve any when (if) we get out of 
>the hybrid and into the full-digital mode.

    Performance in full digital is the real "pig in a poke" about HD 
as developed by Ibiquity.  As I read their white papers, when we (the 
industry) turn the analog off, the _existing_ IBAC carriers get 
turned up, and we get to add additional IBOC carriers where the 
analog was, but at a lower level than the IBAC carrier groups.

    This means that the receivers must be able to receive 
'interleaved' carrier groups, where a lower-first-adjacent interferer 
will have it's high-level upper IBAC carrier group within the area 
where the desired station's low-level IBOC carriers will be.

    Ibiquity's drawing of this is excerpted here:
                www.loudandclean.com/digital.jpg

    This may, or may not work well in the real world, and no amount 
of lab testing or pre-deployment testing with two or three stations 
can come close to telling us what it will be like when we flip the 
big switch and convert the whole industry to digital-only on that 
great day in the future.

    But We Can All Hope For The Best.

Grady