Rubber ducky antenna
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The rubber ducky antenna (or rubber duck aerial) is an
electrically short An electrically small or electrically short antenna is an Antenna (radio), antenna much shorter than the wavelength of the signal it is intended to transmit or receive. Electrically short antennas are generally less efficient and more challenging t ...
monopole antenna A monopole antenna is a class of radio antenna consisting of a straight rod-shaped conductor, often mounted perpendicularly over some type of conductive surface, called a ground plane. The driving signal from the transmitter is applied, o ...
that functions somewhat like a base-loaded
whip 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 ...
. It consists of a springy wire in the shape of a narrow
helix A helix () is a shape like a corkscrew or spiral staircase. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, ...
, sealed in a rubber or plastic jacket to protect the antenna.. A note at the bottom of the page says this page is not copyrighted, and text from this page has been quoted verbatim in this article Rubber ducky antenna is a form of normal-mode
helical antenna A helical antenna is an antenna consisting of one or more conducting wires wound in the form of a helix. A helical antenna made of one helical wire, the most common type, is called ''monofilar'', while antennas with two or four wires in a ...
. Electrically short antennas like the rubber ducky are used in portable handheld radio equipment at VHF and UHF frequencies in place of 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, tro ...
whip 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 ...
, which is inconveniently long and cumbersome at these frequencies. Many years after its invention in 1958, the rubber ducky antenna became the antenna of choice for many portable
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 transmit ...
devices, including
walkie-talkie A walkie-talkie, more formally known as a handheld transceiver (HT), is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald Hings, radio engineer Alfred J. Gross, ...
s and other portable
transceiver In radio communication, a transceiver is an electronic device which is a combination of a radio ''trans''mitter and a re''ceiver'', hence the name. It can both transmit and receive radio waves using an antenna, for communication purposes. The ...
s,
scanners ''Scanners'' is a 1981 Canadian science fiction horror film written and directed by David Cronenberg and starring Stephen Lack, Jennifer O'Neill, Michael Ironside, and Patrick McGoohan. In the film, "scanners" are psychics with unusual telepathic ...
and other devices where safety and robustness take precedence over electromagnetic performance. The rubber ducky is quite flexible, making it more suitable for handheld operation, especially when worn on the belt, than earlier rigid telescoping antennas.


Origin of the name

Two rumors link the naming of the antenna with the Kennedy family. In the early 1960s the rubber ducky became the antenna of choice for personal
walkie-talkie A walkie-talkie, more formally known as a handheld transceiver (HT), is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald Hings, radio engineer Alfred J. Gross, ...
transceivers used by police and security services, including the
U.S. Secret Service The United States Secret Service (USSS or Secret Service) is a federal law enforcement agency under the Department of Homeland Security charged with conducting criminal investigations and protecting U.S. political leaders, their families, and ...
, which guards the President of the United States. According to one rumor, the young
Caroline Kennedy Caroline Bouvier Kennedy (born November 27, 1957) is an American author, attorney, and diplomat serving in the Biden administration as the United States Ambassador to Australia since 2022. She previously served in the Obama administration as th ...
, daughter of President
John F. Kennedy John Fitzgerald Kennedy (May 29, 1917 – November 22, 1963), often referred to by his initials JFK and the nickname Jack, was an American politician who served as the 35th president of the United States from 1961 until his assassination ...
, named the flexible device when she pointed at one on an agent's transceiver and said, "rubber ducky". On the other hand, Dr. Thomas A. Clark, a senior scientist with
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...
, claims to have named it after listening to one of
Vaughn Meader Abbott Vaughn Meader (March 20, 1936 – October 29, 2004) was an American comedian, impersonator, musician, and film actor. Meader began his career as a musician but later found fame in the early 1960s after the release of the 1962 comedy reco ...
's comedies about the Kennedy family. An alternative name is based on the short stub format: the "stubby antenna".


Description

Before the rubber ducky, antennas on portable radios usually consisted of quarter-wave
whip 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 ...
s, rods whose length was one-quarter of the
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, tro ...
of the radio waves used. In the VHF range where they were used, these antennas were long, making them cumbersome. They were often made of telescoping tubes that could be retracted when not in use. To make the antenna more compact,
electrically short An electrically small or electrically short antenna is an Antenna (radio), antenna much shorter than the wavelength of the signal it is intended to transmit or receive. Electrically short antennas are generally less efficient and more challenging t ...
antennas, shorter than one-quarter wavelength, began to be used. Electrically short antennas have considerable capacitive reactance, so to make them
resonant Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscilla ...
at the operating frequency an
inductor An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a c ...
(
loading coil A loading coil or load coil is an inductor that is inserted into an electronic circuit to increase its inductance. The term originated in the 19th century for inductors used to prevent signal distortion in long-distance telegraph transmission c ...
) is added in
series Series may refer to: People with the name * Caroline Series (born 1951), English mathematician, daughter of George Series * George Series (1920–1995), English physicist Arts, entertainment, and media Music * Series, the ordered sets used in ...
with the antenna. Antennas which have these inductors built into their bases are called base-loaded whips. The rubber ducky is an electrically short quarter-wave antenna in which the inductor, instead of being in the base, is built into the antenna itself. The antenna is made of a narrow
helix A helix () is a shape like a corkscrew or spiral staircase. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, ...
of wire like a spring, which functions as the needed inductor. The springy wire is flexible, making it less prone to damage than a stiff antenna. The spring antenna is further enclosed in a plastic or rubber-like covering to protect it. The technical name for this type of antenna is a normal-mode helix. Rubber ducky antennas are typically 4% to 15% of a wavelength long; that is, 16% to 60% of the length of a standard quarter-wave whip.


Effective aperture

Because the length of this antenna is significantly smaller than a wavelength the effective
aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...
, if 100% efficient, would be approximately: Chapter 3, The antenna as an aperture, p. 30. :A_e = \frac Like other electrically short antennas the rubber ducky has poorer performance (less
gain Gain or GAIN may refer to: Science and technology * Gain (electronics), an electronics and signal processing term * Antenna gain * Gain (laser), the amplification involved in laser emission * Gain (projection screens) * Information gain in de ...
) due to losses and thus considerably less gain than a quarter-wave whip. However it has somewhat better performance than an equal length base loaded antenna. This is because the inductance is distributed throughout the antenna and so allows somewhat greater current in the antenna.


Performance

Rubber ducky antennas have lower
gain Gain or GAIN may refer to: Science and technology * Gain (electronics), an electronics and signal processing term * Antenna gain * Gain (laser), the amplification involved in laser emission * Gain (projection screens) * Information gain in de ...
than a full size quarter-wavelength antenna, reducing the range of the radio. They are typically used in short-range
two way radio A two-way radio is a radio that can both transmit and receive radio waves (a transceiver), unlike a broadcast receiver which only receives content. It is an audio (sound) transceiver, a transmitter and receiver in one unit, used for bidirec ...
s where maximum range is not a requirement. Their design is a compromise between antenna gain and small size. They are difficult to characterize electrically because the current distribution along the element is not
sinusoidal A sine wave, sinusoidal wave, or just sinusoid is a mathematical curve defined in terms of the '' sine'' trigonometric function, of which it is the graph. It is a type of continuous wave and also a smooth periodic function. It occurs often in m ...
as is the case with a thin linear antenna. In common with other inductively loaded short monopoles, the rubber ducky has a high
Q factor In physics and engineering, the quality factor or ''Q'' factor is a dimensionless parameter that describes how underdamped an oscillator or resonator is. It is defined as the ratio of the initial energy stored in the resonator to the energy los ...
and thus a narrow
bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...
. This means that as the frequency departs from the antenna's designed center frequency, its SWR increases and thus its efficiency falls off quickly. This type of antenna is often used over a wide frequency range, e.g. 100–500 MHz, and over this range its performance is poor, but in many mobile radio applications there is sufficient excess signal strength to overcome any deficiencies in the antenna.


Design rules

* If the coils of the spring are wide (a large diameter), relative to the length of the array, the resulting antenna will have narrow bandwidth. * Conversely, if the coils of the spring are narrow, relative to the length of the array, the resulting antenna will have its largest possible bandwidth. * If the antenna is resonant, and the spring has a large diameter, the impedance will be well below 50  Ω, tending towards 0 Ω with large inductors as the structure starts to resemble a series-tuned circuit with little
radiation resistance Radiation resistance, \ R_\mathsf\ or \ R_\mathsf\ , is proportional to the part of an antenna's feedpoint electrical resistance that is caused by power loss from the emission of radio waves from the antenna. Radiation resistance is an ''effecti ...
. * If the antenna is resonant, and the spring has a small diameter, the impedance will increase towards 70 Ω. From these rules, one can surmise that it is possible to design a rubber ducky antenna that has about 50 Ω impedance at its feed-point, but a compromise of bandwidth may be necessary. Modern rubber ducky antennas such as those used on cell phones are tapered in such a way that few performance compromises are necessary.


Variations

Some rubber ducky antennas are designed quite differently than the original design. One type uses a spring only for support. The spring is electrically shorted out. The antenna is therefore electrically a linear element antenna. Some other rubber ducky antennas use a spring of non-conducting material for support and comprise a collinear array antenna. Such antennas are still called rubber ducky antennas even though they function quite differently (and often better) than the original spring antenna.


See also

*
Amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communic ...
*
Balun A balun (from "balanced to unbalanced", originally, but now dated from "balancing unit") is an electrical device that allows balanced and unbalanced lines to be interfaced without disturbing the impedance arrangement of either line. A balun c ...
*
Driven element {{Unreferenced, date=April 2016 In a multielement antenna array (such as a Yagi–Uda antenna), the driven element or active element is the element in the antenna (typically a metal rod) which is electrically connected to the receiver or transmi ...
*
Isotropic radiator An isotropic radiator is a theoretical point source of electromagnetic or sound waves which radiates the same intensity of radiation in all directions. It has no preferred direction of radiation. It radiates uniformly in all directions over a ...
*
Omnidirectional antenna In radio communication, an omnidirectional antenna is a class of antenna which radiates equal radio power in all directions perpendicular to an axis (azimuthal directions), with power varying with angle to the axis (elevation angle), declining t ...
*
Shortwave listening Shortwave listening, or SWLing, is the hobby of listening to shortwave radio broadcasts located on frequencies between 1700 kHz and 30 MHz. Listeners range from casual users seeking international news and entertainment programming, to hobbyist ...
*
Whip 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 ...


References

{{Antenna types Radio frequency antenna types