What is NVIS

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.

NVIS Propagation and How it Works:

NVIS propagation is a method of radio wave propagation that is particularly useful for short-range communications, typically within a few hundred kilometers. It involves transmitting radio waves vertically upwards so that they bounce off the ionosphere and back down towards the earth, allowing for reliable communication over relatively short distances.

In this blog, we will discuss how NVIS propagation works, its advantages and limitations, and some applications where it is commonly used.

How NVIS Propagation Works:

NVIS propagation utilizes high frequency (HF) radio waves in the range of 3 to 30 MHz, which are capable of penetrating the ionosphere and reaching the earth’s surface. When a radio wave is transmitted vertically upwards towards the ionosphere, it is refracted or bent back towards the earth due to the ionosphere’s properties. The angle at which the radio wave is transmitted is critical in determining the distance it will travel.

In NVIS propagation, the radio waves are transmitted at an angle of approximately 80 to 90 degrees, which causes them to be refracted and returned to earth at a steep angle, usually between 60 and 90 degrees. The radio waves then travel along the earth’s surface, allowing for reliable communication over relatively short distances.

Advantages of NVIS Propagation:

NVIS propagation has several advantages over other methods of radio wave propagation, particularly for short-range communications:

  1. Low antenna height: NVIS propagation requires a relatively low antenna height, usually less than 1/4 wavelength. This makes it ideal for portable or mobile radio stations, where a tall antenna may not be practical.
  2. Low power requirements: NVIS propagation can be achieved with relatively low transmitter power, usually less than 100 watts. This makes it ideal for emergency communications or field operations where power may be limited.
  3. Reliable communication: NVIS propagation provides reliable communication over short distances, even in mountainous or hilly terrain, where line-of-sight communication may be blocked.
  4. It provides reliable communication in areas with rugged terrain, such as mountainous regions, where traditional radio waves may be blocked by the terrain.

Limitations of NVIS Propagation:

Despite its advantages, NVIS propagation has some limitations:

  1. Limited range: NVIS propagation is limited to relatively short distances, usually within a few hundred kilometers. It is not suitable for long-distance communication.
  2. Interference: NVIS propagation can be susceptible to interference from nearby radio stations operating on the same frequency.
  3. Time of day and season: NVIS propagation is affected by the time of day and season, as the ionosphere’s properties change over time. NVIS propagation is most effective during daylight hours and during the winter months when the ionosphere is more stable.

Applications of NVIS Propagation:

NVIS propagation is used in several applications where reliable communication over short distances is required. These include:

  1. Emergency communications: NVIS propagation is often used in emergency communications, such as disaster relief efforts, where reliable communication over short distances is essential.
  2. Military operations: NVIS propagation is used in military operations, particularly in mountainous or hilly terrain, where line-of-sight communication may be blocked.
  3. Amateur radio: NVIS propagation is popular among amateur radio operators who operate portable or mobile stations and require reliable communication over short distances.

In conclusion, NVIS propagation is a useful method of radio wave propagation for short-range communications. It provides reliable communication over relatively short distances with low antenna height and power requirements. However, it is limited to short distances and can be affected by interference and the time of day and season. NVIS propagation is commonly used in emergency

  • What is NVIS?
    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 … Continued