NVIS antenna for 160 m with extremely good ground
The NVIS antenna is a very unique antenna and is used for short distance sky wave Ionospheric skip communication under favorable propagation conditions on the lower frequency HF bands. Unlike most of the antennas that are named after their structural architecture or the name of the inventor, the NVIS antenna is among the very few that are named after their radiation characteristic or pattern. NVIS stands for "Near Vertical Incidence Skywave". This represents the radiation characteristic of this unique antenna. Structurally NVIS antennas can be designed in various ways as long as the radiation pattern character conforms to NVIS.
HamSphere NVIS antennas are built using horizontal wire dipoles oriented in a manner to produce the desired lobe pattern. By nature a typical NVIS antenna concentrates most of its radiated energy in the vertical or near vertical region. Most of the energy is radiated vertically skywards. Hence, the reflection from the ionosphere bounces back at close distance from the transmitting antenna. HF radio NVIS is very useful for establishing short distance HF communication up to a typical maximum range of 800 Km or less. NVIS also comes in very handy in hilly terrain where a typical VHF/UHF link may not be practically feasible due to the shadow of hills blocking signal between valleys. However, since NVIS signal arrives at the receiver almost vertically from the sky after reflecting from the Ionospheric canopy it allows almost total coverage in a mountainous terrain.
HamSphere NVIS antennas have been made available on the lower frequency HF bands of HS4 to leverage its properties and provide excellent communication over short and short-medium distances. These antennas are good performers.