I'm not sure if this answers your question, but any unlicensed communicate device has limitations on the amount of power it's allowed to radiate. Generally, th

I'm not sure if this answers your question, but any unlicensed communicate device has limitations on the amount of power it's allowed to radiate. Generally, that's the limiting factor in how far-reaching the signal is. Of course, you could transmit in a very narrow angle using antennas and get quick respectable distances, but then you lose omnidirection.