Wire Antenna - Revision history

Carlb at 00:56, 9 April 2009

2009-04-09T00:56:17Z

← Older revision		Revision as of 17:56, 8 April 2009
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	Refer to the article on [[impedance matching]] for more details on connecting transceivers to [[feedline]] and [[feedline]] to antennas.		Refer to the article on [[impedance matching]] for more details on connecting transceivers to [[feedline]] and [[feedline]] to antennas.


			{{antennas}}

TimVK4YEH at 05:30, 31 December 2008

2008-12-31T05:30:17Z

← Older revision		Revision as of 22:30, 30 December 2008
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			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.		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.

TimVK4YEH: changed page link to match existing page

2008-07-03T09:45:54Z

changed page link to match existing page

← Older revision		Revision as of 02:45, 3 July 2008
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	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 [[~~coax~~]] 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.		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 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.

YL: Cleaned up text. Removed references to impedance mismatching, which is too complex for a general article and not limited to wire antennas. We need to move that to a separate detail article.

2008-05-21T02:15:44Z

Cleaned up text. Removed references to impedance mismatching, which is too complex for a general article and not limited to wire antennas. We need to move that to a separate detail article.

← Older revision		Revision as of 19:15, 20 May 2008
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	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]]. When a ~~dipole oscillates~~ current~~, in sync with the radio's RF output during~~ a ~~transmission~~, 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.		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 [[coax]] 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 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. ~~This works but there are losses at the connection~~ due to [[~~impedance~~]] ~~mismatch~~.		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.		The feedpoint impedance of a horizontal [[dipole]] various dramatically depending on the electrical height above ground.

	For example an [[80 metres\|80m]] horizontal [[dipole]] 132 feet long and 66 feet high (1/4 [[wavelength]] above ground) has a feedpoint [[impedance]] of 84 ohms. This would create a mismatch of 1.68:1 [[SWR\|VSWR]] if fed with 50 ohm [[coax]]. The same antenna installed only 18 feet above ground (7 percent of a [[wavelength]]) has an [[impedance]] of 45 ohms with a mismatch of only 1.1:1 [[SWR\|VSWR]]. (However, the radiation pattern of the lower antenna would put more signal at high elevation angles, suitable for local [[QSO\|QSOs]], but it would be inferior for [[DX]].)

	Refer to the article on [[impedance matching]] for more details on connecting transceivers to [[feedline]] and [[feedline]] to antennas.		Refer to the article on [[impedance matching]] for more details on connecting transceivers to [[feedline]] and [[feedline]] to antennas.

YL: Added more text. Ultimately I think the content of this section doesn't belong under "Wire", since it applies to all antennas. We should think about moving it.

2008-04-14T00:43:46Z

Added more text. Ultimately I think the content of this section doesn't belong under "Wire", since it applies to all antennas. We should think about moving it.

← Older revision		Revision as of 17:43, 13 April 2008
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	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 dipole. When a dipole oscillates current, in sync with the radio's RF output during a transmission, 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.		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]]. When a dipole oscillates current, in sync with the radio's RF output during a transmission, 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 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. This works but there are losses at the connection due to impedance mismatch.		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. This works but there are losses at the connection due to [[impedance]] mismatch.

	The feedpoint impedance various dramatically depending on the electrical height above ground.		The feedpoint impedance of a horizontal [[dipole]] various dramatically depending on the electrical height above ground.

	For example an 80m horizontal dipole ~~at 66ft. equal to~~ 1/4 wavelength above ground has a feedpoint impedance of 84 ohms. This would create a mismatch of 1.68:1 VSWR. ~~Now take the~~ same antenna ~~and install it~~ only ~~18ft~~ above ground~~, equal to~~ 7 percent of a wavelength~~, and it now~~ has an impedance of 45 ohms with a mismatch of only 1.1:1 VSWR.		For example an [[80 metres\|80m]] horizontal [[dipole]] 132 feet long and 66 feet high (1/4 [[wavelength]] above ground) has a feedpoint [[impedance]] of 84 ohms. This would create a mismatch of 1.68:1 [[SWR\|VSWR]] if fed with 50 ohm [[coax]]. The same antenna installed only 18 feet above ground (7 percent of a [[wavelength]]) has an [[impedance]] of 45 ohms with a mismatch of only 1.1:1 [[SWR\|VSWR]]. (However, the radiation pattern of the lower antenna would put more signal at high elevation angles, suitable for local [[QSO\|QSOs]], but it would be inferior for [[DX]].)

	~~A better way is~~ to ~~make or purchase a "balun". A balun matches~~ the impedance ~~of the radio to the impedance of the dipole~~ more ~~closely. This increases the power actually transferred~~ to ~~the upper legs of the dipole. (Balun stands for BALanced~~ to ~~UNbalanced~~.)		Refer to the article on [[impedance matching]] for more details on connecting transceivers to [[feedline]] and [[feedline]] to antennas.

YL: Wire moved to Wire Antenna: Need "antenna" in the title.

2008-03-29T18:29:46Z

Wire moved to Wire Antenna: Need "antenna" in the title.

← Older revision	Revision as of 11:29, 29 March 2008
(No difference)

Ke4uyp at 12:52, 8 February 2008

2008-02-08T12:52:31Z

← Older revision		Revision as of 05:52, 8 February 2008
Line 1:		Line 1:
	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 dipole. When a dipole oscillates current, in sync with the radio's RF output during a transmission, 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.		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 dipole. When a dipole oscillates current, in sync with the radio's RF output during a transmission, 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 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. This works but there are losses at the connection due to impedance mismatch. A better way is to make or purchase a "balun". A balun matches the impedance of the radio to the impedance of the dipole more closely. This increases the power actually transferred to the upper legs of the dipole. (Balun stands for BALanced to UNbalanced.)		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. This works but there are losses at the connection due to impedance mismatch.

			The feedpoint impedance various dramatically depending on the electrical height above ground.

			For example an 80m horizontal dipole at 66ft. equal to 1/4 wavelength above ground has a feedpoint impedance of 84 ohms. This would create a mismatch of 1.68:1 VSWR. Now take the same antenna and install it only 18ft above ground, equal to 7 percent of a wavelength, and it now has an impedance of 45 ohms with a mismatch of only 1.1:1 VSWR.

			A better way is to make or purchase a "balun". A balun matches the impedance of the radio to the impedance of the dipole more closely. This increases the power actually transferred to the upper legs of the dipole. (Balun stands for BALanced to UNbalanced.)

Pentaquark: Dipole

2008-02-07T18:36:41Z

Dipole

New page

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 dipole. When a dipole oscillates current, in sync with the radio's RF output during a transmission, 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 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. This works but there are losses at the connection due to impedance mismatch. A better way is to make or purchase a "balun". A balun matches the impedance of the radio to the impedance of the dipole more closely. This increases the power actually transferred to the upper legs of the dipole. (Balun stands for BALanced to UNbalanced.)