How Far You, and Your Radio, Can See VHF and UHF radio propagation is often referred to as line of sight . To give you an idea of what that is, here are a few examples. The actual radio horizon is usually a tiny bit further than the visual horizon, as much as 15 percent at some frequencies.
Height is everything.
Not only the height of one antenna, but the height of the other. As you can see, when altitudes start being measured in thousands of feet, the horizon starts to really stretch outwards. BUT it is going to make a big difference in the efficiency of the radiation, being outside and mounted high and clear in an optimum place, above at least some of the surrounding vegetation etc. Often condo dwellers can get remarkable VHF ranges by hanging up a roll up J-pole in an optimally exposed spot on their lanai. When their height above ground, which can be significant if they are on the 20th or 30th floor, is combined with height above sea level, which even in Honolulu can be several hundred feet, they end up with a rather impressive radio horizon.