Discone antenna
Wideband vertical antenna with disc and cone structure.
A discone antenna is a type of monopole derived from a biconical antenna, where one cone is swapped out for a flat disc. It is typically set up vertically, with the disc on top and the cone below. This antenna is omnidirectional, vertically polarized, and has gain comparable to a dipole, but its standout feature is an exceptionally wide bandwidth—it can cover a frequency range of up to roughly 10 to 1. Its radiation pattern in the vertical plane is fairly narrow, so it is most sensitive toward the horizon and less so for signals coming from nearby.
The design was patented by Armig G. Kandoian of New York City on February 6, 1945, under U.S. patent number US 2368663 for a "Broad band antenna," assigned to Federal Telephone and Radio Corporation (later merged with ITT Corporation). The patent application was filed on May 15, 1943. Kandoian noted that advances in ultra-high frequency radio for aircraft communication and direction finding required small, rigid antennas with low wind resistance, and his invention aimed to meet those needs.
A properly built discone is as efficient as a narrower-band antenna when used for transmitting. The extra bandwidth comes from the controlled taper and large termination radius of the cone. The cone shape and flat disc spread out the local electric field, which cuts down on stored energy in the field, lowering the antenna's Q and reducing losses. The elevation pattern may show distortion from grating lobes. The standing wave ratio (SWR) is typically 1.5:1 or less over several octaves. The antenna has three main parts: the disc, the cone, and an insulator.
The disc should have a diameter of 0.7 times a quarter wavelength at the antenna's lowest frequency. The feed point is at the disc's center, usually connected to a 50-ohm coaxial cable—the center conductor goes to the disc, and the outer conductor to the cone. The cone's length should be a quarter wavelength at the lowest operating frequency, and its angle is generally between 25 and 40 degrees. The disc and cone are separated by an insulator, whose dimensions affect the antenna's properties, especially near the high-frequency limit.
For construction, a discone can be made from solid metal sheet, like copper, which works well for small indoor UHF antennas (e.g., for Wi-Fi).
- Patent number
- US 2368663
- Patent title
- Broad band antenna
- Patent date
- February 6, 1945
- Patent applicant
- Armig G. Kandoian
- Assignor
- Federal Telephone and Radio Corporation
- Frequency range ratio
- up to approximately 10:1
- Typical swr
- 1.5:1 or less over several octaves
Lore & Background
On February 6, 1945, Armig G. Kandoian of New York City was awarded U.S. patent number US 2368663 "Broad band antenna" (assignor to Federal Telephone and Radio Corporation, later merged with ITT Corporation), from an application made on May 15, 1943. The patent noted the need for small, rigid antennas suitable for aircraft communication and direction finding, with low wind resistance. The discone antenna has a useful frequency range of at least 10 to 1. When employed as a transmitting antenna, a properly constructed discone is just as efficient as an antenna designed for a more limited frequency range. The extra bandwidth comes from the controlled taper and large termination radius of the cone. The cone shape and flat disk disperse the local electric field, reducing stored energy in the electric field, reducing antenna Q while also reducing losses. The elevation pattern might be distorted with grating lobes. SWR 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 should have an overall diameter of 0.7 times a quarter wavelength of the antenna's lowest 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 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 disc and cone must be separated by an insulator, the dimensions of which determine some of the antenna's properties, especially near its high frequency limit.
Reader's Guide
The discone antenna's wideband coverage makes it attractive in commercial, military, amateur radio and radio scanner applications. Its inherently wideband nature permits it to broadcast undesirable spurious emissions from faulty or improperly filtered transmitters. 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, simplifying construction and reducing wind loading. The spokes may be made of stiff wire, brazing rods or even coat hanger wire. The minimum number of rods comprising the disc and cone is often quoted as being from 8 to 16. A vertical whip may be affixed to the center of the disc in order to extend the low frequency response, but this compromises efficiency at lower frequencies. Rather than be a true discone the functional mode changes to that of an asymmetrical vertical dipole with a thin upper element. In this configuration, at lower frequencies with a vertical element mounted above the disc, the antenna behaves like a sloped radial ground plane antenna.
Did You Know?
- The discone antenna was patented by Armig G. Kandoian on February 6, 1945.
- Its frequency range ratio can reach up to approximately 10:1.
Frequently Asked Questions
Who is behind the Discone antenna?
The design was patented by Armig G. Kandoian on February 6, 1945, under US patent 2368663 titled "Broad band antenna." It was assigned to Federal Telephone and Radio Corporation.
What are the Discone antenna's standout abilities?
Its defining trait is an extraordinarily wide operating bandwidth, capable of covering a frequency span of roughly 10 to 1 with a single structure. It also radiates omnidirectionally with vertical polarization, making it a versatile all-around performer.
What does the Discone antenna look like in its standard form?
It is a vertical monopole built from a flat disc mounted on top of a cone, essentially a biconical antenna with one cone swapped for a disc. That disc-and-cone silhouette is its instantly recognizable shape.
How does the Discone antenna's gain compare to other antennas?
Its gain sits roughly on par with a simple dipole, so it does not deliver a major strength boost over that baseline. Its real advantage lies in bandwidth and structural simplicity rather than in raw directional gain.
What is the Discone antenna's radiation pattern like?
In the vertical plane the pattern is fairly narrow, meaning the antenna is most sensitive to signals arriving near the horizon. It is noticeably less effective at picking up signals from very close or high-elevation sources.
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