Total posts : 45366
Heh-heh … well, of course, laws of physics apply. But, there are just an unknown number and effects of variables on such low power in any given Part 15 installation. Therefore, experimentation is part and parcel of any such installation, regardless of whether it all comes in a box, or is built from a collection of parts.
And of course a major factor is the receiver. Compare a cheap little clock radio with a quality general class receiver with a longwire antenna.