- Free space attenuation results from signal radiating outward in all directions
- Signal power weakens with the square of the distance travelled – double the distance signal power drops by a factor of four (inverse square law). Doubling distance halves signal voltage
- Line of sight propagation (normal mode at VHF/UHF) approximates the free space model
- Limit of line of sight is known as the radio horizon, which increases as antenna height increases