Beverage antenna
Encyclopedia
The Beverage Antenna is a relatively inexpensive but very effective long wire receiving antenna
used by amateur radio
, shortwave
listening, and longwave
radio
DX
ers and military applications. Harold H. Beverage
experimented with receiving antennas similar to the Beverage antenna in 1919 at the Otter Cliffs Radio Station
. By 1921, Beverage long wave receiving antennas up to nine miles (14 km) long had been installed at RCA's Riverhead, New York, Belfast, Maine, Belmar, New Jersey, and Chatham, Massachusetts receiver stations. The antenna was patented in 1921 and named for its inventor Harold H. Beverage
. Perhaps the largest Beverage antenna—an array of four phased Beverages three miles (5 km) long and two miles (3 km) wide—was built by AT&T in Houlton, Maine
for the first transatlantic telephone system opened in 1927.
While these antennas provide excellent directivity, a large amount of space is required. Beverage antennas are highly directional
and physically far too large to be practically rotated so installations often use multiple antennas to provide a choice of azimuthal coverage.
A Beverage consists of a wire one or two wavelengths long (hundreds of feet at HF to several kilometres for longwave). A resistor connected to a ground rod terminates the end of the antenna pointed to the target area, a 470 ohm non-inductive resistor provides excellent results for most soils. A 50 or 75 ohm coaxial transmission line connects the receiver to the opposite end of the antenna through an impedance-matching transformer
. Some Beverage antennas use a two-wire design that allows reception in two directions from a single Beverage antenna. Other designs use sloped ends where the center of the antenna is six to eight feet high and both ends of the antenna gradually slope downwards towards the termination resistor and matching transformer.
long wire antenna becomes uni-directional
by placing it close to the lossy earth and by terminating one end of the wire with a non-inductive resistor with a resistance approximately matched to the surge impedance of the antenna. This was the fundamental discovery in his 1921 patent.
The Beverage Antenna relies on "wave tilt" for its directive properties. At low and medium frequencies, a vertically polarized radio frequency electromagnetic wave traveling close to the surface of the earth with finite ground conductivity sustains a loss that produces an electric field component parallel to the Earth's surface. If a wire is placed close to the earth and approximately at a right angle to the wave front, the incident wave generates RF currents traveling along the wire, propagating from the near end of the wire to the far end of the wire. The RF currents traveling along the wire add in phase
and amplitude
throughout the length of the wire, producing maximum signal strength at the far end of the antenna where a receiver is typically connected. RF signals arriving from the receiver-end of the wire also increase in strength as they travel to end of the antenna terminated in a resistor, where most of the energy propagating in that direction is absorbed.
Radio waves propagate by the ionosphere
at medium or high frequencies (MF or HF) typically arrive at the Earth's surface with wave tilts of approximately 5 to 45 degrees. Ionospheric wave tilt allows the directivity inducing mechanism described above to produce excellent directivity in Beverage antennas operated at MF or HF.
While Beverage antennas have excellent directivity, because they are close to lossy earth they do not produce absolute gain (typically -20 to -10 dBi). This is rarely a problem, because the antenna is used at frequencies where there are high levels of atmospheric radio noise. The antenna has very low radiation resistance (less than one ohm) and will rarely be utilized for transmitting. The Beverage antenna is a popular receiving antenna because it offers excellent directivity over a broad bandwidth, albeit with relatively large size.
Directivity
is a function of the length of the antenna. While directivity begins to develop at a length of only 0.25 wavelength, directivity becomes more significant at one wavelength and improves steadily until the antenna length reaches a length of about two wavelengths. Its generally accepted among Beverage antenna experts that directivity no longer improves when the antenna is longer than two wavelengths. Beverages longer than two wavelengths suffer from the phase incoherency of the incoming waves over distances of several wavelengths, resulting in phase incoherency of the currents induced in the antenna that degrades the directivity of the antenna.
The Beverage antenna is most frequently deployed as a single wire. A dual wire variant is sometimes utilized for rearward null steering or for bidirectional switching. The antenna can also be implemented as an array of two to 128 or more elements in broadside
, endfire, and staggered
configurations offering significantly improved directivity otherwise very difficult to attain at these frequencies. A four element broadside/staggered Beverage array was used by AT&T at their longwave telephone receiver site in Houlton, Maine
. Very large phased Beverage arrays of 64 elements or more have been implemented for receiving antennas for Over-the-horizon radar
systems.
wire, between one and two wavelengths long, running parallel to the Earth's surface from the receiver towards the direction of the desired signal. The wire is suspended by insulated supports approximately two meters above the ground. A 470 ohm non-inductive resistor is installed from the far end of the wire to a ground rod, although this value is not critical.
Typically a length of 50 ohm or 75 ohm coaxial cable
would be used for connecting the receiver to the antenna endpoint. A matching transformer should be inserted between any such low-impedance transmission line and the higher 470 ohm impedance of the antenna. A transformer with a turns-ratio of 3:1 would provide an impedance transformation of 9:1 which will match the antenna to a 50 ohm transmission line. Alternatively, a transformer with a turns-ratio of 5:2 would provide an impedance transformation of 6.25:1 which will match the antenna to a 75 ohm transmission line.
As an expediency, the transmission line can be connected directly to the end of the antenna and a ground rod usually with satisfactory results.
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
used by amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
, shortwave
Shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
listening, and longwave
Longwave
In radio, longwave refers to parts of radio spectrum with relatively long wavelengths. The term is a historic one dating from the early 20th century, when the radio spectrum was considered to consist of long, medium and short wavelengths...
radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
DX
DXing
DXing is the hobby of tuning in and identifying distant radio or television signals, or making two way radio contact with distant stations in amateur radio, citizens' band radio or other two way radio communications. Many DXers also attempt to receive written verifications of reception from the...
ers and military applications. Harold H. Beverage
Harold Beverage
Dr. Harold Henry "Bev" Beverage is perhaps most widely known today for his invention and development of the wave antenna, which came to be known as the Beverage antenna and which for the last few decades has seen a resurgence in use within the amateur radio and broadcast DXing hobbyist communities...
experimented with receiving antennas similar to the Beverage antenna in 1919 at the Otter Cliffs Radio Station
Otter Cliffs Radio Station
U.S. Naval Radio Station Otter Cliffs was a United States Navy radio receiver facility located in Acadia National Park on Mount Desert Island, south of Bar Harbor, Maine.The station was commissioned on August 28, 1917, under the command of Lt...
. By 1921, Beverage long wave receiving antennas up to nine miles (14 km) long had been installed at RCA's Riverhead, New York, Belfast, Maine, Belmar, New Jersey, and Chatham, Massachusetts receiver stations. The antenna was patented in 1921 and named for its inventor Harold H. Beverage
Harold Beverage
Dr. Harold Henry "Bev" Beverage is perhaps most widely known today for his invention and development of the wave antenna, which came to be known as the Beverage antenna and which for the last few decades has seen a resurgence in use within the amateur radio and broadcast DXing hobbyist communities...
. Perhaps the largest Beverage antenna—an array of four phased Beverages three miles (5 km) long and two miles (3 km) wide—was built by AT&T in Houlton, Maine
Houlton, Maine
Houlton is a town in Aroostook County, Maine, on the United States – Canada border, located at . As of the 2010 census, the town population was 6,123. It is perhaps best known as being at the northern terminus of Interstate 95 and for being the birthplace of Samantha Smith...
for the first transatlantic telephone system opened in 1927.
While these antennas provide excellent directivity, a large amount of space is required. Beverage antennas are highly directional
Directional antenna
A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive and reduced interference from unwanted sources....
and physically far too large to be practically rotated so installations often use multiple antennas to provide a choice of azimuthal coverage.
A Beverage consists of a wire one or two wavelengths long (hundreds of feet at HF to several kilometres for longwave). A resistor connected to a ground rod terminates the end of the antenna pointed to the target area, a 470 ohm non-inductive resistor provides excellent results for most soils. A 50 or 75 ohm coaxial transmission line connects the receiver to the opposite end of the antenna through an impedance-matching transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
. Some Beverage antennas use a two-wire design that allows reception in two directions from a single Beverage antenna. Other designs use sloped ends where the center of the antenna is six to eight feet high and both ends of the antenna gradually slope downwards towards the termination resistor and matching transformer.
Technical Description
Harold Beverage discovered in 1920 that an otherwise nearly bidirectionalBidirectional
The term "bidirectional" may refer to:*Anything that can move in two directions*A roadway that carries traffic moving in opposite directions*A tram or train or any other vehicle that can be controlled from either end and can move forward or backward with equal ease without any need to be turned...
long wire antenna becomes uni-directional
Uni-directional
Unidirectional refers to an object that moves in only one direction at one time.It can refer to:*In communications theory, it is referred to as simplex communication or using ITU standards it refers to half-duplex signaling behavior....
by placing it close to the lossy earth and by terminating one end of the wire with a non-inductive resistor with a resistance approximately matched to the surge impedance of the antenna. This was the fundamental discovery in his 1921 patent.
The Beverage Antenna relies on "wave tilt" for its directive properties. At low and medium frequencies, a vertically polarized radio frequency electromagnetic wave traveling close to the surface of the earth with finite ground conductivity sustains a loss that produces an electric field component parallel to the Earth's surface. If a wire is placed close to the earth and approximately at a right angle to the wave front, the incident wave generates RF currents traveling along the wire, propagating from the near end of the wire to the far end of the wire. The RF currents traveling along the wire add in phase
Phase (waves)
Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.-Formula:The phase of an oscillation or wave refers to a sinusoidal function such as the following:...
and amplitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
throughout the length of the wire, producing maximum signal strength at the far end of the antenna where a receiver is typically connected. RF signals arriving from the receiver-end of the wire also increase in strength as they travel to end of the antenna terminated in a resistor, where most of the energy propagating in that direction is absorbed.
Radio waves propagate by the ionosphere
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
at medium or high frequencies (MF or HF) typically arrive at the Earth's surface with wave tilts of approximately 5 to 45 degrees. Ionospheric wave tilt allows the directivity inducing mechanism described above to produce excellent directivity in Beverage antennas operated at MF or HF.
While Beverage antennas have excellent directivity, because they are close to lossy earth they do not produce absolute gain (typically -20 to -10 dBi). This is rarely a problem, because the antenna is used at frequencies where there are high levels of atmospheric radio noise. The antenna has very low radiation resistance (less than one ohm) and will rarely be utilized for transmitting. The Beverage antenna is a popular receiving antenna because it offers excellent directivity over a broad bandwidth, albeit with relatively large size.
Directivity
Directivity
In electromagnetics, directivity is a figure of merit for an antenna. It measures the power density the antenna radiates in the direction of its strongest emission, versus the power density radiated by an ideal isotropic radiator radiating the same total power.An antenna's directivity is a...
is a function of the length of the antenna. While directivity begins to develop at a length of only 0.25 wavelength, directivity becomes more significant at one wavelength and improves steadily until the antenna length reaches a length of about two wavelengths. Its generally accepted among Beverage antenna experts that directivity no longer improves when the antenna is longer than two wavelengths. Beverages longer than two wavelengths suffer from the phase incoherency of the incoming waves over distances of several wavelengths, resulting in phase incoherency of the currents induced in the antenna that degrades the directivity of the antenna.
The Beverage antenna is most frequently deployed as a single wire. A dual wire variant is sometimes utilized for rearward null steering or for bidirectional switching. The antenna can also be implemented as an array of two to 128 or more elements in broadside
Broadside
A broadside is the side of a ship; the battery of cannon on one side of a warship; or their simultaneous fire in naval warfare.-Age of Sail:...
, endfire, and staggered
Staggered
In organic chemistry, a staggered conformation is a chemical conformation of an ethane-like moiety abcX-Ydef in which the substituents a,b,and c are at the maximum distance from d,e,and f...
configurations offering significantly improved directivity otherwise very difficult to attain at these frequencies. A four element broadside/staggered Beverage array was used by AT&T at their longwave telephone receiver site in Houlton, Maine
Houlton, Maine
Houlton is a town in Aroostook County, Maine, on the United States – Canada border, located at . As of the 2010 census, the town population was 6,123. It is perhaps best known as being at the northern terminus of Interstate 95 and for being the birthplace of Samantha Smith...
. Very large phased Beverage arrays of 64 elements or more have been implemented for receiving antennas for Over-the-horizon radar
Over-the-horizon radar
Over-the-horizon radar, or OTH , is a design concept for radar systems to allow them to detect targets at very long ranges, typically up to thousands of kilometers...
systems.
Implementation
A single wire Beverage Antenna is typically a single straight copperCopper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
wire, between one and two wavelengths long, running parallel to the Earth's surface from the receiver towards the direction of the desired signal. The wire is suspended by insulated supports approximately two meters above the ground. A 470 ohm non-inductive resistor is installed from the far end of the wire to a ground rod, although this value is not critical.
Typically a length of 50 ohm or 75 ohm coaxial cable
Coaxial cable
Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...
would be used for connecting the receiver to the antenna endpoint. A matching transformer should be inserted between any such low-impedance transmission line and the higher 470 ohm impedance of the antenna. A transformer with a turns-ratio of 3:1 would provide an impedance transformation of 9:1 which will match the antenna to a 50 ohm transmission line. Alternatively, a transformer with a turns-ratio of 5:2 would provide an impedance transformation of 6.25:1 which will match the antenna to a 75 ohm transmission line.
As an expediency, the transmission line can be connected directly to the end of the antenna and a ground rod usually with satisfactory results.
Patents
- U.S. Patent 1,381,089 Jun 7, 1921 Radio Receiving System - the Beverage antenna
- U.S. Patent 1,434,984 Nov 7, 1922 Radio Receiving System - the bidirectional Beverage antenna
- U.S. Patent 1,434,985 Nov 7, 1922 Radio Receiving System - using a Beverage antenna with multiple receivers
- U.S. Patent 1,434,986 Nov 7, 1922 Radio Receiving System - a Beverage antenna with selective circuits to eliminate interference from adjacent wavelengths
- U.S. Patent 1,487,308 Mar 18, 1924 Radio Receiving System - improvements to the directivity of the Beverage Antenna
- U.S. Patent 1,556,122 Oct 6, 1925 Radio Receiving System - improvements to the directivity of the Beverage Antenna
- U.S. Patent 1,658,740 Feb 7, 1928 Radio Receiving System - broadside phasing of two of more Beverage antennas for improved directivity
- U.S. Patent 1,768,239 Reducing interference received through a sidelobe of a Beverage antenna
- U.S. Patent 1,816,614 Wave Antenna - improvements to the directivity of the Beverage Antenna
- U.S. Patent 1,821,402 Staggered Beverage antennas and phased staggered Beverage antennas
External links
- AA3PX Antenna design page
- AMANDX antenna page
- W8JI Beverage antenna construction - definitive guide
- W0BTU's Practical, comprehensive information concerning Two-wire Beverage antennas
- VE4QRP "baby beverage" antenna
- SWDXER ¨The SWDXER¨ - with general SWL information and radio antenna tips.
- Harold H. Beverage article on 200 meter Beverages
- Map of the AT&T Transoceanic Telephone Receiver Site in Houlton, Maine
- U.S. Naval Radio Station Otter Cliffs
- The Wave Antenna, A New Type of Highly Directive Antenna, Proceedings of the AIEE, February 1923
- Beverage Antennas for High Frequency Communications, Direction Finding and Over the Horizon Radars, Canadian Research Center
- The Wave Antenna, Edmund Laport
