Is a NVIS antenna directional?
Dipoles only exhibit directionality once they reach 1/2 wavelengths above ground. However, NVIS antennas are located from 1/4 to 1/10 wavelength above ground. Since it is omni-directional, dipole orientation is not important. The higher the angle, the lower the frequency needed to work properly.
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 …
How tall is a dipole antenna for NVIS?
The dipole is installed horizontally, held about one meter (3-4 feet) above ground by three ski poles, one in the center and one at each end. It’s low height is what makes this antenna onlysuitable for NVIS duty. No DX possible with this antenna!
Is the NVIS dipole good for CW or SSB?
That’s easy to achieve for CW but not quite as easy for SSB. Reducing noise on receive is critical to obtain workable SSB intelligibility. Receiving copyable SSB is made much easier in the near no-noise environment that the NVIS dipole provides.
What is the theory of the NVIS antenna?
MILITARY NVIS ANTENNA THEORY AND DESIGN Ron P Milione AAR2JD/W2TAP Introduction A properly designed Near Vertical Incident Skywave (NVIS) antenna will have a directivity pattern that will maximize transmission and reception at high angles while rejecting low angle, long range noise.
What kind of lead does a portable NVIS antenna use?
The portable antenna, depicted above, is made with 300 ohms twin lead. You could use 450 ohm ladder line, but the twin lead is lighter and more manageable for easy portability for field work. The twin conductors, at the extremitiesof the antenna, are connected together. Note the open gap in the center, above the feed point.