I continue to read elsewhere sweeping statements that a legal Part 15 statement will not leave your own property. Of course, there's no accompanying math or physics to prop up those statements at all. That's because there are none possible. Perhaps those who continue to put this msinformation forward believe that if they continue to say it, eventually it will become like fact.
But the truth is that the range of a Part 15 signal is entirely dependent on the receiving equipment and obstructions between the receiving and transmitting antennas.
My recent research on receiver sensitivity revealed that there are any number of car receivers that are capable of receiving signals in the 1-1.5uv range with up to 20db quieting. A Part 15 legal signal with field strength of 250uv/m at 3 meters has a field strength of 5uv at 150 meters (around 500 feet) line of sight, more than strong enough to be heard by those car receivers. And for some, that range could extend out to 800 feet or more, line of sight.
There's also no doubt that the typical portable or handheld FM radio has a much more difficult time hearing a Part 15 legal signal. That same research showed that the typical portable might hear a signal out to about 40-45 meters (around 150 feet) and a typical handheld would be lucky to hear it at 20 meters (maybe 75 feet).
So while it is true that portable and handheld receivers might not hear a Part 15 legal signal 'off your property' (depending on the property size, of course), a good car radio or the best home stereo receivers (other research has showed that they have pretty much the same sensitivity as car receivers) could hear it much, much farther.
QED.