Antenna loading - Revision history

Carlb: /* Antenna tuners */

2009-06-05T23:08:53Z

Antenna tuners

← Older revision		Revision as of 16:08, 5 June 2009
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	== Antenna tuners ==		== Antenna tuners ==
	An external antenna tuner is often used in conjunction with HF antennas to tune antennas to resonance within a band. In most cases, these are π or T networks in which a variable inductor and capacitors are used to tune for lowest [[SWR\|standing-wave ratio]] as seen by the transmitter.		An external [[antenna tuner]] is often used in conjunction with HF antennas to tune antennas to resonance within a band. In most cases, these are π or T networks in which a variable inductor and capacitors are used to tune for lowest [[SWR\|standing-wave ratio]] as seen by the transmitter.

	An antenna tuner must be rated for the full power of the transmitter and both manual and automatically-tuned versions of these units are commercially available. Some late-model transceivers may integrate this functionality, although for best results any tuner or loading coil needs to be at or near the antenna itself.		An antenna tuner must be rated for the full power of the transmitter and both manual and automatically-tuned versions of these units are commercially available. Some late-model transceivers may integrate this functionality, although for best results any tuner or loading coil needs to be at or near the antenna itself.

Carlb: /* Antenna tuners */

2009-06-05T22:15:03Z

Antenna tuners

← Older revision		Revision as of 15:15, 5 June 2009
Line 28:		Line 28:
	An external antenna tuner is often used in conjunction with HF antennas to tune antennas to resonance within a band. In most cases, these are π or T networks in which a variable inductor and capacitors are used to tune for lowest [[SWR\|standing-wave ratio]] as seen by the transmitter.		An external antenna tuner is often used in conjunction with HF antennas to tune antennas to resonance within a band. In most cases, these are π or T networks in which a variable inductor and capacitors are used to tune for lowest [[SWR\|standing-wave ratio]] as seen by the transmitter.

	An antenna tuner must be rated for the full power of the transmitter, and both manual and automatically-tuned versions of these units are commercially available. Some late-model transceivers may integrate this functionality, although for best results any tuner or loading coil needs to at or near the antenna itself.		An antenna tuner must be rated for the full power of the transmitter and both manual and automatically-tuned versions of these units are commercially available. Some late-model transceivers may integrate this functionality, although for best results any tuner or loading coil needs to be at or near the antenna itself.

	== See also ==		== See also ==

Carlb at 22:13, 5 June 2009

2009-06-05T22:13:33Z

← Older revision		Revision as of 15:13, 5 June 2009
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	A standard [[dipole]] antenna is resonant if constructed with a length of one-half wavelength. A [[vertical antenna]] (effectively half a dipole operating against a ground plane) is resonant at one-quarter wavelength. Resonance may also be observed at each of the odd multiples.		A standard [[dipole]] antenna is resonant if constructed with a length of one-half wavelength. A [[vertical antenna]] (effectively half a dipole operating against a ground plane) is resonant at one-quarter wavelength. Resonance may also be observed at each of the odd multiples.

	For most VHF and UHF antennas, a half or quarter wavelength is reasonable in size and can be readily accommodated in all but the smallest handheld transceiver antenna designs. The same is not true of HF antennas on the radioamateur bands or mobile antennas for 27MHz (11-metre) CB operation. [[Mobile antenna]]s are inherently limited in the amount of available space, yet reducing an antenna's length increases its resonant frequency.		For most VHF and UHF antennas, a half or quarter wavelength is reasonable in size and can be readily accommodated in all but the smallest handheld transceiver antenna designs. The same is not true of HF antennas on the radioamateur bands or mobile antennas for 27MHz (11-metre) CB operation. [[Mobile antenna]]s are inherently limited by the amount of available space, yet reducing an antenna's length increases its resonant frequency.

	A loading coil may be used, on its own or in conjunction with a [[capacity hat]], to tune the antenna to resonance at a lower frequency. One coil placed in the centre or at the base of a single-band vertical antenna is sufficient, but a single-band dipole will require two coils - one in each element of the dipole.		A loading coil may be used, on its own or in conjunction with a [[capacity hat]], to tune the antenna to resonance at a lower frequency. One coil placed in the centre or at the base of a single-band vertical antenna is sufficient, but a single-band dipole will require two coils - one in each element of the dipole.

Carlb: /* See also */

2009-06-05T22:10:31Z

Carlb: /* External links */

2009-06-05T22:09:29Z

External links

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 * [http://www.ve3sqb.com VE3SQB ANTENNA DESIGN PROGRAMS]
 * [http://webpages.charter.net/crstrode/calcs/RFcalcs.htm WA7CS RF Calculator Page]
 == External links ==

Carlb: New page: An '''antenna loading coil''' is an inductor placed in series with an antenna element in order to lower the antenna's resonant frequency. A standard dipole antenna is resonant if con...

2009-06-05T22:02:15Z

New page: An '''antenna loading coil''' is an inductor placed in series with an antenna element in order to lower the antenna's resonant frequency. A standard dipole antenna is resonant if con...

New page

An '''antenna loading coil''' is an inductor placed in series with an antenna element in order to lower the antenna's resonant frequency.

A standard [[dipole]] antenna is resonant if constructed with a length of one-half wavelength. A [[vertical antenna]] (effectively half a dipole operating against a ground plane) is resonant at one-quarter wavelength. Resonance may also be observed at each of the odd multiples.

For most VHF and UHF antennas, a half or quarter wavelength is reasonable in size and can be readily accommodated in all but the smallest handheld transceiver antenna designs. The same is not true of HF antennas on the radioamateur bands or mobile antennas for 27MHz (11-metre) CB operation. [[Mobile antenna]]s are inherently limited in the amount of available space, yet reducing an antenna's length increases its resonant frequency.

A loading coil may be used, on its own or in conjunction with a [[capacity hat]], to tune the antenna to resonance at a lower frequency. One coil placed in the centre or at the base of a single-band vertical antenna is sufficient, but a single-band dipole will require two coils - one in each element of the dipole.

For multiband HF antennas, different loading coils (or adjustable coils) are needed for coverage of each band.

== Design calculators ==
An antenna with a loading coil cannot be modelled electrically as an element in which the inductor has been replaced by the corresponding length of straight wire. An inductor will behave differently as current at one end of an inductor creates a magnetic field which immediately induces currents at the opposite end. An inductor also adds electrical resistance to an antenna, incurring a penalty in radiation efficiency compared to a full-size antenna.

There are a number of online calculators which can determine a suitable value and position for inductive loading coils based on an antenna's dimensions and desired resonant frequency.

Verticals:
* [http://vk1od.net/calc/slvaf.htm Antenna Factor of short tuned vertical with concentrated loading], VK1OD

Dipoles:
* [http://www.rac.ca/tca/IndoorAntenna_2.html Horizontal Indoor Antenna #2], VE3KL
* [http://eweb.chemeng.ed.ac.uk/jack/radio/software/loading.html Antenna Loading Coil Calculation], OA4/KA2OIG

Various antenna calculation programmes are also available for download.
* [http://www.ve3sqb.com VE3SQB ANTENNA DESIGN PROGRAMS]
* [http://webpages.charter.net/crstrode/calcs/RFcalcs.htm WA7CS RF Calculator Page]

== External links ==
* [http://www.w8ji.com/mobile_and_loaded_antenna.htm Inductors and Loading Coil Current (Mobile and Loaded Antennas)], W8JI
* [http://www.nonstopsystems.com/radio/frank_radio_antenna_beam.htm Frank's N4SPP Ham Radio home-built mini yagi beam dipole antenna]

{{antennas}}

← Older revision		Revision as of 15:10, 5 June 2009
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	* [[Antenna tuner]]		* [[Antenna tuner]]
	* [[Capacity hat]]		* [[Capacity hat]]
	* [[Screwdriver antenna]]		* [[Screwdriver antenna]], a mobile [[vertical antenna]] with a built-in remotely-adjustable antenna loading coil

	== External links ==		== External links ==