Ham Radio General Class Practice Test

Which is an advantage of an NVIS antenna?

1. Low vertical angle radiation for working stations out to ranges of several thousand kilometers

2. High vertical angle radiation for working stations within a radius of a few hundred kilometers

3. High forward gain

4. All of these choices are correct

The correct answer is: High vertical angle radiation for working stations within a radius of a few hundred kilometers

An NVIS (Near Vertical Incidence Skywave) antenna is specifically designed to radiate radio waves at a high angle, which effectively allows for communication with stations located within a radius of a few hundred kilometers. This characteristic makes NVIS antennas particularly advantageous for short-range amateur radio communications, especially during conditions where standard propagation may not work effectively. By focusing on high vertical angle radiation, NVIS antennas take advantage of the lower ionospheric layers, allowing signals to bounce back to Earth at steep angles, thus enhancing local communications. This capability is invaluable for emergency communications and local community networking and is often utilized in situations where traditional long-distance radiating methods are less effective due to varying propagation conditions. While lower angle radiation (as described in the first choice) and high forward gain (as described in the third choice) are beneficial features for long-distance communication, they do not apply to the NVIS operational strategy which emphasizes short-range effectiveness. Therefore, the high vertical angle radiation defining NVIS antennas is what underpins its advantage for specific communication scenarios.