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Richard Fry

wrote
The problem I see with these is that, as distance approaches 0, KW
approahes oo and what I'm looking for shouldn't be greater than the
transmitter's erp. ... What would be much more useful would be a
listing of stations that provide--st least the theoretical baseline
value (i.e., not considering intervening local terrain or one's
receiver sensitivity and antenna gain)--a given mV/m or mW at that
point (thus listing 100 W stations out to 15 km, whereas 50 KW
stations out to 75 km and 100 KW to 130 km would be listed).
_________________

Using the known ERP from the transmit antenna it is possible using various
algorithms to calculate the field strength that will exist at a distant
point for some defined condition(s). The FCC has done this for AM/FM/TV
broadcast stations, and the techniques are available to the public via the
FCC's website. Various broadcast-oriented commercial software programs also
are available to do this, although they are expensive.

For AM stations, the distant field is a function of the frequency, ERP,
path length, ground conductivity, terrain roughness, the ionosphere, and the
time of day.

For FM/TV stations, distant field is a function of ERP, the heights of the
transmit and receive antennas, reflections, atmospheric conditions, path
length, and the terrain profile along the path.

These are not simple relationships. For example, in order to provide
essentially equal signal strengths over most of their useful coverage areas,
the ERP needed from an FM station with a "high" antenna can be much less
than if the antenna is lower. Here is a plot showing this...
http://i62.photobucket.com/albums/h8...ssBCompare.gif

Unfortunately, there is no simple solution answering your queries.

RF