the whole point of the docket 80-90 was to "drop-in" fm allocations
wherever possible to add first or second local services in communities
all over the country. Of course, some of the drop-ins (mostly the lower
powered "A" allocations, limited to 3, now 6 kW) fell in larger areas,
like Tucson. Often they were limited to a certain number of miles from
the center of a town or area, and provided less than optimal coverage of
these larger markets. However, there was a great demand for the
allocations, since they could be sold quickly, for big bucks, at least
until the bust of the late 80's.
All of which is a long winded answer to "what is a drop-in." It's a
station sited *by* the FCC, usually within some limitations, so it would
allow the most stations possible to fit.
On the other hand, there was (and likely are) a number of professional
engineers who make a living filing "mutually exclusive" applications.
What they do is identify a large market where a good facility would be a
money winner, and then avoid the comparative hearings by filing on a
small town, just far enough away to cripple the potential station in the
major market. For the right amount of money, the smaller station would be
"happy to move a few miles, or go DA."
AN even worse variation, is to set up an MX sitation, and then refuse to
deal. The larger market station is dropped. The smaller station is built,
and, wonder of wonders, files a CP to move to the larger market.
Of course all of this is harder these days than it used to be. But there
are an amazing number of applications still being filed to frustrate the
1:300/11.3 on FidoNet