Mark Howell wrote:
On-channel boosters are not quite the same thing as translators.
Boosters are used when terrain obstacles block parts of the predicted
coverage contour of an FM station. They are allowed only to fill such
"holes," not to extend what would otherwise be the station's coverage
area. The SF bay area is full of them, as the topography prevents any
FM station from reaching full coverage without boosters.

I didn't think station-owned translators were allowed to extend the
station's coverage area either? (but independently-owned translators
are; IIRC the FCC does not allow independently-owned boosters)

Seems to me a large proportion of *commercial* translators are fillins,
not range extenders. Of course the situation is very different for
non-commercial translators!
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com