On 1/12/2012 5:26 PM, SMS wrote:
I think you're well aware of the answer. Not every FM station will be
able to use 400 Khz. Some can have only one sideband at maximum power. A
small percentage can't use either sideband. Life is rough when you're
trying to maximize spectral efficiency.
In fact a very small percentage will be able to use 400 KHz at their
assigned frequencies. We had this discussion once before, since the
Ibiquity spec posted he
http://www.nrscstandards.org/SG/NRSC-5-B/1026sE.pdf
shows double the occupied bandwidth for a digital signal.
You said that most stations are spaced far enough from their
adjacent-channel neighbors that this wouldn't be a problem, despite
numerous examples of adjacent-channel interference right here in the Bay
Area. The fact is that this would work somewhat in the plains of
Western Nebraska, but never in the Bay Area. Moving just one station
has a severe domino effect. Let me give you an example of one such
situation right here in the Bay Area:
The South Bay will soon have a full-power FM station on 93.7. Why?
93.7 KXZM in Felton will be increasing power. Why?
KXSM in Hollister is moving from 93.5 to 93.1 and increasing power. Why?
KOSO in Patterson moved from 93.1 to 92.9 and decreased power. Why?
So 93.1 KHLX in Pollock Pines could move their transmitter closer to
Sacramento.
How did Pollock Pines get a radio station? Somebody bought a radio
station in Susanville and moved it to Pollock Pines.
This is just one example of how tightly sandwiched signals are
throughout the US. A transaction in Susanville has an effect on the Bay
Area. Spacing is already so close that adjacent-channel HD interference
is very obvious to those who know what it is. Those who don't know the
difference between regular static and digital noise just turn off their
radio. That is why those of us who care about the real future of
broadcasting and know how to use a spectrum analyzer would like to see
the Ibiquity scheme just go away and be replaced with a truly viable
digital radio medium.
Dave B.