Discone antenna

Discone antenna
Mounted discone antenna designed for VHF and UHF coverage.
Discone made of solid copper sheets, theoretically covering 700MHz to 2GHz.

A discone antenna is a version of a biconical antenna in which one of the cones is replaced by a disc. It is usually mounted vertically, with the disc at the top and the cone beneath.

Omnidirectional, vertically polarized and exhibiting unity gain, it is exceptionally wideband, offering a frequency range ratio of up to ~10:1. The radiation pattern in the horizontal plane is quite narrow, making its sensitivity highest in the plane tangent to the Earth's surface.

Contents

History

On February 6, 1945, Armig G. Kandoian of New York was awarded U.S. patent number 2,368,663 (assignor to Federal Telephone and Radio Corporation (later merged with ITT Corporation) for a "broad band antenna", from an application made on May 15, 1943.

Excerpt from the Kandoian patent:

In keeping with progress made during the last few years in the development of ultra-high frequency radio technique, and applications thereof to aircraft communication, direction finding, and so forth, it has become necessary to develop special antennas and antenna systems suitable for installation on such aircraft. Flying conditions are such that these antennas must necessarily be small and rigid in their construction and also offer a minimum of wind resistance, in order that the flying efficiency of the aircraft will be unimpaired. In accordance with my invention I have provided a small rigid antenna suitable for mounting on the surface of the fuselage or other component of the airplane structure and in certain embodiments I have also provided a streamlined protecting shield or housing covering or so cooperating with the construction of the antenna system as to greatly reduce wind resistance.

[1]

Applications

The discone's wideband coverage makes it attractive in commercial, military, amateur radio and radio scanner applications.

When employed as a transmitting antenna, it is often less efficient than an antenna designed for a more limited frequency range. SWR (standing wave ratio) is typically ~2:1 over the range of the design frequency to the second harmonic and ~3.1 thereafter.

The discone's inherently wideband nature permits it to broadcast undesirable spurious emissions from faulty or improperly filtered transmitters.

Construction materials

A discone may be made from solid metal sheet (often copper), which is practical for small indoor UHF antennas, such as for Wi-Fi.

At lower frequencies a sufficient number of metal wires or rods in a spoke configuration is often used to approximate a solid surface. This simplifies construction and reduces wind loading.

The spokes may be made of stiff wire, brazing rods or even coat hanger wire.

The optimal number of rods comprising the disc and cone is often quoted as being from 8 to 16.

Components

A discone antenna typically has at least three major components: the disc, the cone, and the insulator.

The disc

The disc should have an overall diameter of 0.7 times a quarter wavelength of the antenna's minimum frequency.

The antenna's feed point is at the center of the disc. It is usually fed with 50-ohm coaxial cable, with the center conductor connected to the disc, and the outer conductor to the cone.

The cone

The length of the cone should be a quarter wavelength of the antenna's minimum operating frequency.

The cone angle is generally from 25 to 40 degrees.

The insulator

The disc and cone must be separated by an insulator, the dimensions of which determine some of the antenna's properties.

Extending low-frequency response

A vertical whip may be placed affixed vertically to the disc in order to extend the low frequency response, but this may reduce efficiency at higher frequencies. In this configuration, at lower frequencies the discone may more closely resemble a ground plane antenna or a coaxial dipole.

See also

References

External links



Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • discone antenna — skritulinė kūginė antena statusas T sritis radioelektronika atitikmenys: angl. discone antenna vok. Antenne aus Scheiben Konuskombination, f; Diskonantenne, f rus. диск коническая антенна, f pranc. antenne discône, f; antenne disque cône, f …   Radioelektronikos terminų žodynas

  • discone antenna — A wideband antenna formed of a disc and a cone, whose apex approaches and becomes common with the outer conductor or the coaxial feed at its extremity. The center conductor terminates at the center of the disc that is perpendicular to the axis of …   Aviation dictionary

  • Antenna (radio) — Whip antenna on car …   Wikipedia

  • Microstrip antenna — In telecommunication, there are several types of microstrip antennas (also known as printed antennas) the most common of which is the microstrip patch antenna or patch antenna. A patch antenna is a narrowband, wide beam antenna fabricated by… …   Wikipedia

  • Biconical antenna — Biconical antennaA biconical antenna consists of an arrangement of two conical conductors, which is driven by potential, charge, or an alternating magnetic field (and the associated alternating electric current) at the vertex. The conductors have …   Wikipedia

  • Parabolic antenna — A parabolic satellite communications antenna at Erdfunkstelle Raisting, the biggest facility for satellite communication in the world, in Raisting, Bavaria, Germany. It has a Cassegrain type feed. A parabolic antenna is an antenna that uses a… …   Wikipedia

  • Dipole antenna — A schematic of a half wave dipole antenna connected to an unbalanced coaxial cable. Better practice is to connect the balanced dipole to the unbalanced line with a balun. A dipole antenna is a radio antenna that can be made of a simple wire, with …   Wikipedia

  • Loop antenna — A shortwave loop antenna A loop antenna is a radio antenna consisting of a loop (or loops) of wire, tubing, or other electrical conductor with its ends connected to a balanced transmission line. Within this physical description there are two very …   Wikipedia

  • Monopole antenna — Mast radiator monopole antenna used for broadcasting. AM radio station WARE, Warren, Massachusetts, USA. A monopole antenna is a class of radio antenna consisting of a straight rod shaped conductor, often mounted perpendicularly over some type of …   Wikipedia

  • Rubber Ducky antenna — on a transceiver The Rubber Ducky antenna (or Rubber Duck aerial) is an electrically short monopole antenna which functions somewhat like a base loaded whip antenna and is sealed in a rubber or plastic jacket to protect the antenna.[1]… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”