How Dipole Antenna Works

June 26, 2024 Post a Comment

How dipole antenna works

The dipole antenna is a particularly important form of RF antenna which is very widely used for radio transmitting and receiving applications. The dipole is often used on its own as an RF antenna, but it also forms the essential element in many other types of RF antenna.

How does current flow in a dipole antenna?

The charge and current on the dipole create fields that are perpendicular to each other. The electric field, E, flows from the positive charge to the negative charge placed on the elements by voltage applied to the antenna as shown in Figure 3(a).

How efficient is a dipole antenna?

It can be very close to 100% (or 0 dB) for dish antennas, horn antennas, or half-wavelength dipoles with no lossy materials around them. Mobile phone antennas, or wifi antennas in consumer electronics products, typically have efficiencies from 20%-70% (-7 to -1.5 dB).

Are dipole antennas any good?

They're easy to put up for temporary or Field Day use, and they're also widely used by radio amateurs at home because they're inexpensive and easy to build. Another advantage of dipole antennas is they are very efficient when used at their resonant frequency.

What is dipole antenna wavelength?

The dipole antenna is cut and bent for effective radiation. The length of the total wire, which is being used as a dipole, equals half of the wavelength (i.e., l = λ/2). Such an antenna is called as half-wave dipole antenna. This is the most widely used antenna because of its advantages.

Does a dipole antenna have to be straight?

Dipole antennas need not be installed in a horizontal straight line. They are generally tolerant of bending, sloping or drooping as required by the antenna site. Remember, however, that dipole antennas are RF conductors.

Are antennas AC or DC?

An antenna is an open circuit for DC (though there is an initial current flowing when the voltage is applied, until the capacitor is fully loaded), but is conductive when fed in AC (the feed impedance is actually 73Ω at resonant frequency).

What is the frequency range of dipole antenna?

A dipole antenna with calculable gain over the frequency range 20 MHz to 2.2 GHz. Abstract: The precise measurement of antenna gain in the lower half of the VHF range presents many challenges.

Do antennas have voltage?

The voltage across the antenna elements and the current through them create the electric and magnetic waves, respectively. At the receiver, the electromagnetic wave passing over the antenna induces a small voltage. Thus, the antenna becomes the signal source for the receiver input.

How long is a 20 meter dipole antenna?

20 Meter Dipole at 42 feet.

How do you increase dipole antenna gain?

In order to increase the gain of an antenna, you need to concentrate its effectiveness in the required direction. Two common methods are to concentrate horizontal beamwidth by adding reflectors and directors, thus creating a Yagi beam.

How is the dipole antenna polarized?

Further, the E-field only has one vector component and consequently the fields are linearly polarized. When viewed in the x-y plane (for a dipole oriented along the z-axis), the E-field is in the -y direction, and consequently the dipole antenna is vertically polarized.

Does a dipole antenna need a BalUn?

If a dipole antenna is fed with a coaxial cable from the transceiver, it is always a good idea to use a “BalUn”. BalUn means: Balanced to Unbalanced. This enables us to adapt an unbalanced fed system (coaxial cable) to a balanced antenna system (dipole antenna).

Should a dipole antenna be vertical or horizontal?

Even when far-away ground reflections may cause the directivity of a vertical HF antenna at low take-off angles to be much higher than that of a horizontal HF antenna, its net gain will still be lower at those angles. This makes the horizontal HF antenna a clear winner, at least for what transmission is concerned.

What wire is used for dipole antenna?

The toughest and most flexible of all the wire tested was the thin stainless-steel cable, making it the best overall choice of antenna wire for all conditions.

What is the formula for a dipole antenna?

Dipole length formula Often a formula for the length of a dipole in feet is seen as 468 / frequency. This can be derived by taking the figure of 492 seen in the formula above and multiplying it by the typical A or end effect factor of 0.95.

How is dipole antenna calculated?

When determining how long to make each leg of a Dipole antenna, dividing the frequency in MHz into 468 will give the overall length. To find the half wave, divide that number by two. This will give you the length of each leg of the antenna.

What is antenna formula?

GdB = 10 log10 (4πηA/λ2) GdB is the antenna gain, η is the efficiency, A is the physical aperture area, λ is the wavelength of the signal.

Is dipole antenna directional?

Dipole antennas (or such designs derived from them, including the monopole) are used to feed more elaborate directional antennas such as a horn antenna, parabolic reflector, or corner reflector. Engineers analyze vertical (or other monopole) antennas on the basis of dipole antennas of which they are one half.

Does a dipole antenna need a ground plane?

Answer: No. The 1/2 wave antenna (also called a dipole antenna) is built of two 1/4 wave elements that interact with one another to launch the electro-magnetic wave. It does not require a ground plane to work efficiently.