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R is the radius of the Earth, h is the height of the ground station, H is the height of the air station d is the line of sight distance In the case, when there are two stations involve, e.g. a transmit station on ground with a station height h and a receive station in the air with a station height H , the line of sight distance can be ...
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. [1]: 26‑1 As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. [2]
Fresnel zone: D is the distance between the transmitter and the receiver; r is the radius of the first Fresnel zone (n=1) at point P. P is d1 away from the transmitter, and d2 away from the receiver. The concept of Fresnel zone clearance may be used to analyze interference by obstacles near the path of a radio beam. The first zone must be kept ...
The '4/3 Earth's radius' is a useful rule of thumb to the radio communication engineers when designing such a NLOS link. The 4/3 Earth radius rule of thumb is an average for the Earth's atmosphere assuming it is reasonably homogenised, absent of temperature inversion layers or unusual meteorological conditions.
If the receiver moves to another location along the line, the timing of the signals would change. For instance, if they time the signals at 0.25 and 0.75 ms, they are 75 km from the closer station and 225 from the further. If the receiver moves to the side of the baseline, the delay from both stations will grow. At some point, for instance ...
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Common types of low-gain omnidirectional antennas are the whip antenna, "Rubber Ducky" antenna, ground plane antenna, vertically oriented dipole antenna, discone antenna, mast radiator, horizontal loop antenna (sometimes known colloquially as a 'circular aerial' because of the shape) and the halo antenna.
At lower frequencies, VLF and ELF, the signal will reflect off the ionosphere and ground, allowing the signal to travel great distances in multiple "hops". However, it is very difficult to synchronize multiple stations using these signals, as they might be received multiple times from different directions at the end of different hops.