To install click the Add extension button. That's it.

The source code for the WIKI 2 extension is being checked by specialists of the Mozilla Foundation, Google, and Apple. You could also do it yourself at any point in time.

4,5
Kelly Slayton
Congratulations on this excellent venture… what a great idea!
Alexander Grigorievskiy
I use WIKI 2 every day and almost forgot how the original Wikipedia looks like.
Live Statistics
English Articles
Improved in 24 Hours
Added in 24 Hours
Languages
Recent
Show all languages
What we do. Every page goes through several hundred of perfecting techniques; in live mode. Quite the same Wikipedia. Just better.
.
Leo
Newton
Brights
Milds

Short backfire antenna

From Wikipedia, the free encyclopedia

Comparison between the two antenna types.
Comparison between the two antenna types.

A short backfire antenna (or short back-fire, SBA, SBF or SBFA) is a type of a directional antenna, characterized by high gain, relatively small size, and narrow band. It has a shape of a disc with a straight edge, with a vertical pillar with a dipole acting as the driven element in roughly the middle and a conductive disc at the top acting as a sub-reflector. The bottom disc has the diameter of two wavelengths, and its collar (edge) is quarter the wavelength tall. The center pillar consists of two coaxial tubes (their diameter has to be carefully chosen to give the desired impedance), with a quarter-wavelength slot cut into the outer tube

This structure behaves like a resonant cavity, resulting in a substantial gain in small space.

Short backfire antennas are used in some satellites, and in high-frequency (short-wavelength) communication equipment (often for communication with satellites) on ships and other applications where rugged construction is an advantage. They are also used for wireless LANs. The SBF antenna was invented by Dr. Hermann W. Ehrenspeck of Air Force Cambridge Research Labs based at Hanscom Air Force Base in Bedford, MA and was used for among other purposes, to provide Tactical Satellite Communications for U.S. Army ground forces due to the SBF's portability and gain.

The bandwidth of the antenna can be increased by using a conical main reflector instead of a flat one.

Archery target antenna is an evolution of the short-backfire antenna. The name is derived from its appearance. Its base diameter is 5 wavelengths (5 λ), the rim height is 0.7 λ, the diameter of the small center reflector is 0.7 λ, its height above the base is 0.7 λ as well, the height of the dipole above the base is 0.35 λ, there is one more reflector - an annular reflector - at the same height as the center reflector, with inner diameter 2.2 λ and outer diameter 3.7 λ. [1]

Short backfire antennas are able to achieve high aperture efficiencies, at right cavity size even beyond 100%.[1]

YouTube Encyclopedic

  • 1/1
    Views:
    593 792
  • 3 Wasps That Will Do Anything to Survive

Transcription

See also

References

  1. ^ "Weatherproof UHF & microwave cavity antennas (S53MV)". Retrieved 18 October 2012.
This page was last edited on 30 December 2018, at 15:09
Basis of this page is in Wikipedia. Text is available under the CC BY-SA 3.0 Unported License. Non-text media are available under their specified licenses. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc. WIKI 2 is an independent company and has no affiliation with Wikimedia Foundation.