OTA

Over-the-Air is a colloquial expression which refers to the transmission of a radio frequency signal through the gaseous mediums otherwise known as the lower layers of the Earth's atmosphere

• terrestrial based -- transmission towers
  • typically broadcast (as opposed to narrowcasted) ... i.e. FTA

• to a lesser extent, non-terrestrial based -- satellite transponder ... although not much "air" at the point source (i.e. near vacuous outerspace) ... but the signal does end up traversing through the denser terrestrial airspace
  • both FTA, and encrypted/narrowcast

On the reception/receiver end, OTA properly refers to "Off-the-Air"