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Tuesday, August 16, 2005


HD Radio-Jams your favorite stations!

EXAMPLE TWO: A radio station is not a "point" on a line representing the FM dial's 20mHz bandwidth (from 88.0--108mHz).
A radio station slot is a "channel" encompassing a RANGE of frequencies. A legal FM radio station is currently 200kHz [0.2mHz] of that dial.
Due to the lack of regulation requiring a minimum level of performance for FM receivers ... a large buffer was established in 1963 of three "channels" (also known as "third adjacent channel prohibition") to each side of a station in a local area.
So Q94.5FM uses a range of frequencies centered at 94.5mHz (m="mega" Hz="Hertz", which means "million vibrations a second) on the electromagnetic spectrum of frequencies available to current technology.
Q94.5FM encompasses a 200kHz bandwidth centered at 94.5FM, therefore half (100kHz or 0.1mHz) is updial and half is downdial. So the range is 94.5-0.1=94.4mHz and 94.5+0.1mHz=94.6mHz thus the range is 94.4--94.6mHz.
The DAB-IBOC proposal plans to expand that bandwidth from 200kHz to 430kHz.
Thus Q94.5FM would under IBOC-DAB encompass on the FM dial a range from 94.285--to-- 94.715mHz on the FM dial.
Similarly, (several miles to the East) WTPE 94.9FM's new signal encompasses 94.685--to-- 95.115mHz on the FM dial
Graphically: (ascii charted) Q94.5 94.285 94.715mHz iiiiiiii <0.3mHz of mixed signal! iiiiiiii 94.685 95.115mHz 94.9 Losing the competition provided by 94.9FM for Richmonders with a good radio is bad enough ... but the rural listeners between Richmond and Norfolk will likely lose access to both stations! And unlike with LPFM, there will be no replacement service.

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