Can a vertical antenna be used for NVIS?
Half-wave dipole antennas are great for NVIS, positioned a fraction of a wavelength above the ground. To direct the greatest portion of the transmitted signal vertically, the antenna must be positioned relatively low to the ground. A height of 1/8 to 1/10 wavelength is often used for effective NVIS.
How does a NVIS antenna work?
NVIS only works at frequencies from 2 MHz to 10 MHz. The signal must penetrate the D layer of the ionosphere, and bounce off the F layer. Lower-frequency signals will not penetrate the D layer; higher frequencies will not bounce off the F layer at these sharp angles and just goes out into space.
Is NVIS directional?
Antennas. An NVIS antenna configuration is a horizontally polarized (parallel with the surface of the earth) radiating element that is from 120th wavelength (λ) to 14 wavelength above the ground. Optimum height is about 14 wavelength, and high angle radiation declines only slightly for heights up to about 38 wavelength …
What is NVIS propagation?
NVIS, or Near Vertical Incidence Skywave propagation is a form of ionospheric radio propagation that can be used where radio communications links are needed to cover short distances. It fills the gap between line of sight and the longer distance skip type communications that are normally used at HF.
At what frequencies does Nvis occur?
NVIS communication uses frequencies between approximately 3 and 10 MHz. A comprehensive overview of NVIS research is given, covering propagation, antennas, diversity, modulation and coding.
What is an NVIS?
The New Vehicle Information Statement (NVIS) is a record of a new vehicle and provides basic information on the vehicle, the manufacturer/importer, the authorized dealer who sells it, and on the initial purchaser.
What is the best angle for an inverted V antenna?
For optimal performance, the apex angle of an inverted V antenna should be between 70 and 110 degrees.
How tall is a NVIS antenna for emergency use?
The NVIS antenna described is based on the proven information from the military AS-2259/GR antenna. It will provide excellent short range communications and is easy to set up for emergency or temporary communications. It’s a dual band inverted “V” at a height of 15 feet. The area required (foot print) is approximately 45 feet by 45 feet.
Do you need ground terminal for Cha EmComm II?
The CHA EMCOMM II does not required any ground plane, but will perform better with one (a ground terminal is available for that purpose). This antenna requires a wide range antenna tuner or coupler. Antennas built by Chameleon AntennaTM are versatile, dependable, stealthy, and built to last.
Which is the best propagation mode for NVIS?
NVIS Near Vertical Incidence Skywave (NVIS) is a propagation mode which uses high angle radiation to send signals almost straight up to be reflected back to Earth for very effective short to medium distance communications. This mode of operation makes it ideal for in-state communications during disasters or other emergency situations.
What kind of antenna does the military use?
The military uses a dual band NVIS antenna known as the AS-2259/GR. It consists of two crossed inverted “V” dipoles positioned at right angles to each other and is supported at the center by a 15-foot mast. The antenna was designed for military use from 2 to 10 MHz (some references say 2 to
