A discone antenna is a version of a

biconical antenna In radio systems, a biconical antenna is a broad-bandwidth antenna made of two roughly conical conductive objects, nearly touching at their points.Zhuohui Zhang,''Analysis and design of a broadband antenna for software defined radio'', ProQuest, 2 ...

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 Omnidirectional refers to the notion of existing in every direction. Omnidirectional devices include: * Omnidirectional antenna, an antenna that radiates equally in all directions * VHF omnidirectional range, a type of radio navigation system for ...

, vertically polarized and with gain similar to a

dipole In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways: *An electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple example of this system ...

, it is exceptionally

wideband In communications, a system is wideband when the message bandwidth significantly exceeds the coherence bandwidth of the channel. Some communication links have such a high data rate that they are forced to use a wide bandwidth; other links ma ...

, offering a frequency range ratio of up to approximately 10:1. The

radiation pattern In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: “A ...

in the

vertical plane In astronomy, geography, and related sciences and contexts, a '' direction'' or ''plane'' passing by a given point is said to be vertical if it contains the local gravity direction at that point. Conversely, a direction or plane is said to be hor ...

is quite narrow, making its sensitivity highest in the direction of the horizon and rather less for signals coming from relatively close by.

History

On February 6, 1945, Armig G. Kandoian of

New York City New York, often called New York City or NYC, is the most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the most densely populated major city in the Un ...

was awarded U.S. patent number (assignor to Federal Telephone and Radio Corporation, later merged with ITT Corporation), 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 Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (o ...

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmi ...
technique, and applications thereof to
aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engine ...
communication,
direction finding Direction finding (DF), or radio direction finding (RDF), isin accordance with International Telecommunication Union (ITU)defined as radio location that uses the reception of radio waves to determine the direction in which a radio stati ...
, 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 fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding flu ...
, 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 The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraf ...
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.

Description

The discone antenna has a useful frequency range of at least 10 to 1. 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 In radio engineering and telecommunications, standing wave ratio (SWR) is a measure of impedance matching of loads to the characteristic impedance of a transmission line or waveguide. Impedance mismatches result in standing waves along the trans ...

) is typically 1.5:1 or less over several octaves of frequency. A discone antenna consists of three main parts: the disc, the cone, and the insulator. * The disc: The disc should have an overall diameter of 0.7 times a quarter

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, t ...

of the antenna's lowest

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

. 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 lowest 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, especially on near its high frequency limit.

Construction materials

A discone may be made from solid metal sheet (often

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

), which is practical for small indoor UHF antennas, such as for

Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio wav ...

. 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.

Applications

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

radio scanner A scanner (also referred to as a radio scanner) is a radio receiver that can automatically tune, or ''scan'', two or more discrete frequencies, stopping when it finds a signal on one of them and then continuing to scan other frequencies when the ...

applications. The discone's inherently wideband nature permits it to broadcast undesirable

spurious emission In radio communication, a spurious emission is any component of a radiated radio frequency signal the complete suppression of which would not impair the integrity of the modulation type or the information being transmitted. A radiated signal out ...

s from faulty or improperly filtered

transmitter In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...

Extending low-frequency response

A vertical whip may be affixed to the center of the disc in order to extend the low frequency response, but this may compromise efficiency at higher frequencies. In this configuration, at lower frequencies the discone may more closely resemble a

ground plane antenna A whip antenna is an antenna consisting of a straight flexible wire or rod. The bottom end of the whip is connected to the radio receiver or transmitter. A whip antenna is a form of monopole antenna. The antenna is designed to be flexible so th ...

or a coaxial dipole.

References

External links

UHF Discone Antenna

Parabolic Discone (Michael Lake KD8CIK)

Broadband radial discone antenna: Design, application and measurements

Discone antenna basics
{{Antenna Types Radio frequency antenna types Antennas (radio)