Αποτελέσματα Αναζήτησης
Line-of-sight refers to radio waves which travel directly in a line from the transmitting antenna to the receiving antenna, often also called direct-wave. It does not necessarily require a cleared sight path; at lower frequencies radio waves can pass through buildings, foliage and other obstructions.
Propagation models (PM) are being used to predict: average signal strength at a given distance from the transmitter. variability of the signal strength in close spatial proximity to a particular location. PM can be divided into: large-scale models (mean signal strength for large transmitter receiver separation)
The waves that propagate near the earth’s surface are called GROUND WAVES. This type of propagation is possible when the transmitting and receiving antenna both are closed to the earth’s surface. The ground waves which travel without any reflection are called Direct waves or Space waves.
Space Waves, also known as direct waves, are radio waves that travel directly from the transmitting antenna to the receiving antenna. In order for this to occur, the two antennas must be able to ―see‖ each other; that is there must be a line of sight path between them.
Below the ionospheric penetration frequency, a radiowave will propagate along the Earth's surface, as illustrated in Figure 2-4(a). This mode is called ground wave prop agation, and consists of three components: a direct wave, a ground reflected wave, and a surface wave which is guided along the Earth's surface.
Electromagnetic Wave: Electromagnetic waves are a self-propagating transverse wave of oscillating electric and magnetic fields. The direction of the electric field is indicated in blue, the magnetic field in red, and the wave propagates in the positive x-direction.
25 Οκτ 2012 · This chapter includes general issues related to the radiowaves propagation, transmission media, troposphere, and ionosphere layers. Frequency bands, main kinds of propagations modes, radio services, equivalent radiated power (ERP), and radio noises are listed and discussed in brief.
