NVIS (Near Vertical Incidence Skywave) is a radio communication technique used to communicate over relatively short distances using high-frequency radio waves. The primary advantage of NVIS over other long-distance radio communication techniques is that it can be used to communicate over distances of up to 300 miles, even when there is no direct line-of-sight between the transmitting and receiving antennas.
In traditional long-distance radio communication techniques such as HF (High-Frequency) propagation, radio waves travel in a straight line from the transmitting antenna to the receiving antenna. This technique is effective for long-distance communication over hundreds or even thousands of miles, but it requires a clear line-of-sight between the transmitting and receiving antennas.
In contrast, NVIS radio waves are sent straight up into the atmosphere and then redirected back down towards the earth’s surface. This technique allows radio waves to travel over relatively short distances of up to 300 miles, even when there is no direct line-of-sight between the transmitting and receiving antennas.
NVIS was first developed during World War II as a technique for providing reliable communication over relatively short distances. It was used extensively by the military during the war and has since been adopted by civilian organizations such as emergency responders, disaster relief agencies, and amateur radio operators.
One of the primary advantages of NVIS is that it requires relatively low-power radio transmitters and simple, lightweight antennas. This makes it an ideal technique for use in remote or inaccessible locations where traditional radio communication techniques may not be feasible.
Another advantage of NVIS is that it provides reliable communication in areas with rugged terrain, such as mountainous regions, where traditional radio waves may be blocked by the terrain.
NVIS is also effective in areas with high levels of electromagnetic interference (EMI), such as urban areas or areas with a high concentration of radio equipment. This is because the technique allows radio waves to be directed towards the earth’s surface, reducing the impact of EMI.
In conclusion, NVIS is an effective technique for providing reliable communication over relatively short distances using high-frequency radio waves. It is ideal for use in remote or inaccessible locations, rugged terrain, and areas with high levels of electromagnetic interference. As such, it has become an important tool for emergency responders, disaster relief agencies, and amateur radio operators around the world.