Wire Antenna: Difference between revisions
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Related wiki pages: [[Wire comparison tables]] | |||
The shape of a dipole resembles the letter "T". The middle leg connects the radio to the center of the upper, horizontal legs. There are several ways to make the connection. The simplest has the coax shield connected to one side and the center conductor connected to the other side. | Many amateur radio antenna systems use a simple wire to carry the RF current in such a way as to radiate. One of the simplest is the half-wave center-fed [[dipole]] with [[Coaxial Cable]] feedline. When a radio-frequency oscillating current is applied to a dipole, the [[magnetic field]] generated around the wire expands and contracts very quickly, in most cases millions of times per second. It is the outer most part on the field that is radiated away. | ||
The shape of a [[dipole]] resembles the letter "T". The middle leg, which consists of the [[coax]] feedline, connects the radio to the center of the upper, horizontal legs. There are several ways to make the connection. The simplest has the coax shield connected to one side and the center conductor connected to the other side. However, this can cause [[feedline radiation]] due to [[common-mode currents]]. It is often recommended that a [[balun]] be attached at the feedpoint, but many operators have good success with dipoles that have no baluns. | |||
The feedpoint impedance of a horizontal [[dipole]] various dramatically depending on the electrical height above ground. | |||
Refer to the article on [[impedance matching]] for more details on connecting transceivers to [[feedline]] and [[feedline]] to antennas. | |||
{{antennas}} | |||
Latest revision as of 16:56, 8 April 2009
Related wiki pages: Wire comparison tables
Many amateur radio antenna systems use a simple wire to carry the RF current in such a way as to radiate. One of the simplest is the half-wave center-fed dipole with Coaxial Cable feedline. When a radio-frequency oscillating current is applied to a dipole, the magnetic field generated around the wire expands and contracts very quickly, in most cases millions of times per second. It is the outer most part on the field that is radiated away.
The shape of a dipole resembles the letter "T". The middle leg, which consists of the coax feedline, connects the radio to the center of the upper, horizontal legs. There are several ways to make the connection. The simplest has the coax shield connected to one side and the center conductor connected to the other side. However, this can cause feedline radiation due to common-mode currents. It is often recommended that a balun be attached at the feedpoint, but many operators have good success with dipoles that have no baluns.
The feedpoint impedance of a horizontal dipole various dramatically depending on the electrical height above ground.
Refer to the article on impedance matching for more details on connecting transceivers to feedline and feedline to antennas.
| Antennas | |
| Design | Beam * Dipole * Dish or Parabola * DDRR * Log Periodic (LPDA) * Loop * Mobile and portable * Omnidirectional * Panel * Quad and Quagi * Screwdriver * Small tuned loop * Vertical * Yagi-Uda * Wire and random wire antennas |
| Installation | Antenna Tuners * Capacity hats and loading coils * Cavity filters * Coaxial Cable * Feedlines * Rotators * Towers and Masts * VK2ACY - G5RV coupler |
| Theory | Front-to-back ratio * Impedance matching * SWR * Tower design * Vertical Antenna efficiency * Wire comparison tables |