Editing Very high frequency (section)

==Line-of-sight calculation==
[[File:Rabbit-ears dipole antenna with UHF loop 20090204.jpg|thumb|"Rabbit-ears" VHF [[television antenna]] (the small loop is a separate UHF antenna)]]

VHF transmission range is a function of transmitter power, receiver sensitivity, and distance to the horizon, since VHF signals propagate under normal conditions as a near [[Line-of-sight propagation|line-of-sight]] phenomenon. The distance to the [[radio horizon]] is slightly extended over the geometric line of sight to the horizon, as radio waves are weakly bent back toward the Earth by the atmosphere.

An approximation to calculate the line-of-sight horizon distance (on Earth) is:
*distance in nautical miles = <math>1.23\times\sqrt{  A_\textrm{ft}}</math> where <math>A_\textrm{ft}</math> is the height of the antenna in feet<ref>{{Cite web |last=Senesac |first=David |title=Visual Line of Sight Calculations dependent on Earth's Curvature |url=https://www.davidsenesac.com/Information/line_of_sight.html#:~:text=The%20distance%20to%20the%20horizon,by%2012%20equals%201%20mile.}}</ref>
*distance in kilometers = <math>\sqrt{12.746 \times A_\textrm{m}}</math> where <math>A_\textrm{m}</math> is the height of the antenna in meters.<ref>{{Cite web |title=Distance to the Horizon |url=https://aty.sdsu.edu/explain/atmos_refr/horizon.html }}</ref>

These approximations are only valid for antennas at heights that are small compared to the radius of the Earth. They may not necessarily be accurate in mountainous areas, since the landscape may not be transparent enough for radio waves.

In engineered communications systems, more complex calculations are required to assess the probable coverage area of a proposed transmitter station.<ref>{{Cite web |title=Radio Wave Propagation Theory |url=https://imdpune.gov.in/training/communication/LN_11_60_Radio%20Wave%20Propagation%20Theory.pdf}}</ref>