There is no power setting for any Airport device.
I don't recall the specific functional description but I absolutely do remember being able to adjust the distance at which the device could be seen. At the time we were about 110 from the road and I definitely used a setting that was much less - thinking that it would be extra protection from someone in a car with a laptop.
Perhaps it was something with a different nomenclature (e.g. transmission pattern) but there absolutely was an ability to deal with range.
