| Near Vertical Incidence Skywave |
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Information AboutNear Vertical Incidence Skywave |
| CATEGORIES ABOUT NEAR VERTICAL INCIDENCE SKYWAVE | |
| radio frequency antenna types | |
| nvis | |
| radio frequency propagation | |
| wireless communications | |
| amateur radio | |
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NVIS is employed with an Antenna configured to produce a primary Radiation Lobe nearly in the vertical, hence the name (in other words, the antenna is transmitting straight up). The net result, provided that the transmitter frequency is far enough below the maximum usable frequency, is that the signal is scattered directly back in and around the vicinity of the transmitting station. This differs from other shortwave antenna configurations designed to communicate over very long distances ( DX ), where the angles of the antenna radiation lobes are designed to be much smaller. Because VHF communications are largely Line-of-sight , NVIS is especially effective in local and regional emergency and military communications, when satellite or other modes of communications are unavailable and reliable communication beyond the horizon is necessary. For instance, NVIS was commonly used by the United States in Vietnam and the United Kingdom in Malaysia where the dense jungle terrain would render other modes of propagation ineffective. . To utilize NVIS effectively, both the transmitting station and the receiving station should be similarly configured. EXTERNAL LINKS REFERENCE |
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