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Topic: Antenna effective area

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	FCC Fact Sheet on Placement of Antennas
		For a digital antenna to receive or transmit an acceptable quality signal, the antenna must be installed where it has an unobstructed, direct view of the satellite or other device from which signals are received or to which signals are to be transmitted.
		An antenna that extends out beyond the balcony or patio is usually considered to be in a common area that is not within the scope of the rule.
		Effective January 22, 1999, renters may install antennas within their leasehold, which means inside the dwelling or on outdoor areas that are part of the tenant's leased space and which are under the exclusive use or control of the tenant.
	www.fcc.gov /mb/facts/otard.html (5266 words)

	Antenna (radio) (Site not responding. Last check: 2007-10-26)
		Complex impedance of an antenna is related to the electrical length of the antenna at the wavelength in use.
		The polarization of an antenna is the polarization of the signals it emits.
		The Phased array antenna is a group of independently fed active elements in which the relative phases of the respective signals feeding the elements are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.
	hallencyclopedia.com /Antenna_(radio) (2594 words)

	ipedia.com: Antenna (electronics) Article (Site not responding. Last check: 2007-10-26)
		Typically, antennas are designed to operate in a relatively narrow frequency range.
		Typically an antenna is tuned for a specific frequency, and is effective for a range of frequencies usually centered on that resonant frequency.
		All of these parameters are expressed in terms of a transmission antenna, but are identically applicable to a receiving antenna.
	www.ipedia.com /antenna__electronics_.html (2229 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal
		The parabolic antenna is a high-gain reflector antenna used for radio, television and data communications, and also for radiolocation (RADAR), on the UHF and SHF parts of the electromagnetic spectrum.
		The feed antenna is connected to the associated radio-frequency (RF) transmitting or receiving equipment by means of a coaxial cable transmission line or hollow waveguide.
		Practical considerations of antenna effective area and sidelobe suppression reduce the actual gain obtained to between 35 and 55 percent of this theoretical value.
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=dish_antenna (956 words)

	Antenna directivity and effective area
		Indeed, it is topologically impossible for an antenna to emit transverse waves uniformly in all directions (for the same reason that it is impossible to comb the hair on a sphere in such a manner that there is no parting).
		Clearly, the effective area of an isotropic radiator is the same as the area of a circle whose radius is the reduced wavelength
		Thus, we can visualize the capture area as a rectangle which is the physical length of the antenna in one direction, and approximately one quarter of the wavelength in the other.
	farside.ph.utexas.edu /teaching/jk1/lectures/node83.html (944 words)

	Antenna (electronics) (Site not responding. Last check: 2007-10-26)
		Alternatively, if an antenna is placed into an electromagnetic field, it will produce an alternating voltage (receive) in response to the field.
		A dummy load may have a SWR of 1:1 but an efficiency of 0, as it absorbs all power and radiates none, showing that SWR alone is not an effective measure of an antenna's efficiency.
		At such frequencies, signals are reflected very effectively by the ionosphere; however, at these frequencies there are many forms of natural radio noise, inclding the noise produced by lightning.
	www.brainyencyclopedia.com /encyclopedia/a/an/antenna__electronics_.html (2214 words)

	AntennaWeb
		For multidirectional antennas, allow for some mounting flexibility so that the antenna can be moved a few feet in each direction in order to obtain the best picture on all channels before a permanent mounting position is selected.
		Directional antennas are the most ghost-resistant antennas since they "see" in only one direction and have a tendency not to see the reflected ghost signal.
		The rule applies to viewers who place video antennas on property that they own and that is within their exclusive use or control, including condominium owners and cooperative owners who have an area where they have exclusive use, such as balcony or patio, in which to install the antenna.
	www.antennaweb.org /aw/info.aspx?page=FAQ (3347 words)

	Antenna Types
		This antenna is sold as an FM Band antenna, with dipoles, usually in the "folded" form cut for the FM band.
		In real life, most consumer antennas are not pure Yagi, or log-periodic, but instead are a jumble of rods designed to get the most from the limited boom space over a wide range of channels.
		Medium Wave Antenna: Take half a dipole (1/4 wave wire) and use the earth as the other half, and you get the antenna usually found at a medium wave (AM) broadcast station.
	www.kyes.com /antenna/antennatypes/antennatypes.html (2147 words)

	Articles - Parabolic antenna (Site not responding. Last check: 2007-10-26)
		This antenna is typically a low-gain type such as a half-wave dipole or a small waveguide horn.
		The feed antenna is connected to the associated radio-frequency (RF) transmitting or receiving equipment by means of a coaxial cable transmission line or hollow waveguide.
		Practical considerations of antenna effective area and sidelobe suppression reduce the actual gain obtained to between 35 and 55 percent of this theoretical value.
	www.mildhome.com /articles/Parabolic_antenna (435 words)

	Antenna Link for More Info (Site not responding. Last check: 2007-10-26)
		This is the right way to explain antenna gain as a function of effective area, and I have run into engineers that don't get it.
		This is off topic, but an understanding of effective area can make understandable why, using parabolic antennas of fixed physical dimensions and distance, and ignoring attenuation by the atmosphere, the power transfer between the two antennas will increase as wavelength decreases.
		As the effective area is constant regardless of wavelength, the receiving parabolic gets more power as the wave length shortens since power density on the receiving dish is greater.
	www.kyes.com /antenna/formulas.html (284 words)

	page3
		The main element of the antenna is either a mirror or a lens whose diameter is many wavelengths.
		(In fact, the actual effective area isn't exactly equal to the physical opening area, but it is of a similar size so this estimate is good enough to reveal the problem.) This would require a very ‘deep’ parabolic reflector and and impossibly large lens to collect.
		Hence the effective area of antenna is generally between 90% and 50% of the physical mirror/lens area.
	www.st-andrews.ac.uk /~jcgl/Scots_Guide/RadCom/part7/page3.html (566 words)

	Nikola Tesla Page, Tesla's power receiver
		These antennas behave as if they were much larger than their physical diameter, as if there was an "invisible lens" focusing more of the incoming EM energy upon the antenna.
		This increases the antenna's EA (effective area, or effective aperture.) We can use this process to alter the coupling between the antenna and the surrounding space, but the total energy still follows the conservation law.
		The resonant antenna might be very small, but it would have an intense e-field (or magnetic field if it was a loop antenna), and would reach out and touch the AM tower electrically.
	www.amasci.com /tesla/tesceive.html (7499 words)

	Definition: antenna effective area
		antenna effective area: The functionally equivalent area from which an antenna directed toward the source of the received signal gathers or absorbs the energy of an incident electromagnetic wave.
		Note 1: Antenna effective area is usually expressed in square meters.
		Note 2: In the case of parabolic and horn-parabolic antennas, the antenna effective area is about 0.35 to 0.55 of the geometric area of the antenna aperture.
	www.atis.org /tg2k/_antenna_effective_area.html (104 words)

	Re: Converting SFU to Kelvin (Site not responding. Last check: 2007-10-26)
		The power received by the antenna from the source is: Pr = S Ae / 2 where: Pr = received power from object, W/Hz S = flux density, W/m^2/Hz Ae = antenna effective area, m^2 For a dish antenna Ae is typically 55% of the physical area.
		The factor 1/2 in the equation allows for the polarisation mismatch; the noise is (usually) randomly polarised; an antenna is not.
		If this is not the case, and the object overfills the beam, we have the situation where the whole antenna "sees" the object at temperature Ts.
	www.amsat.org /amsat/archive/amsat-bb/200401/msg00455.html (679 words)

	Wiley-VCH - Visser, Hubregt - Array and Phased Array Antenna Basics
		This easy-to-read volume explains the principles of array and phased array antennas at an introductory level, without relying heavily on a thorough understanding of electromagnetics or even antenna theory.
		Although the principles are explained mathematically, the introduction is based on the array's physical characteristics rather than mathematics.
		3.4 Antenna Effective Area and Vector Effective Length.
	www.wiley-vch.de /publish/en/books/bySubjectEE00/bySubSubjectEE21/0-470-87117-2/?sID=7bc7dc6589155873156e83d82b095133 (191 words)

	Antenna effective area -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-26)
		Antenna effective area -- Facts, Info, and Encyclopedia article
		Note 2: In the case of parabolic and (One of the bony outgrowths on the heads of certain ungulates) horn-parabolic antennas, the antenna effective area is about 0.35 to 0.55 of the geometric area of the (Click link for more info and facts about antenna aperture) antenna aperture.
		Source: from (Click link for more info and facts about Federal Standard 1037C) Federal Standard 1037C
	www.absoluteastronomy.com /encyclopedia/a/an/antenna_effective_area.htm (84 words)

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