|
Just for completeness, there is a reason for some channels to be stronger closer to the ground.
It is a function of propagation physics. The interface between the ground and the air is an interface between two materials (earth and air) that have different dielectric constants. When radio waves encounter this interface, some of that RF energy will propagate along the surface of the interface before dissipating. Most of that energy stays very close to the surface (usually within about 1 wavelength). When the conditions are right (very low direct signal strength and shallow signal approach angle), the cumulative ground wave energy might be more than the energy in the direct signal itself. When that happens, you might see a little bit more energy close to the ground than you would higher up.
In the real world, this "ground gain" is usually not that helpful. In most cases, as you get closer to the ground, you get more random objects (e.g., other buildings, trees, walls, cars, roads, etc.) that affect your signal. The increased scattering effect will probably negate any gains you might see in signal strength. The ground wave might benefit you if all you have are open fields in front of the antenna, but for most people this is not the case.
If it's just a matter of a few dB, then you are probably better off going with a higher antenna that is above most of the surface clutter, even if it means losing a small amount of signal strength.
|