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Topic: Low Gain Antenna

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	SmoothTalker FAQ - Cellular Antennas
		An antenna without gain (0db) radiates energy in all directions equally and antenna with gain redirects or concentrates energy in a certain direction and the gain performance is measured in the direction of the energy concentration.
		It is possible to calculate the effect of antenna placement by measuring the signal level at the phone location and the signal level at the proposed external antenna position and subtracting the loss of a known length of cable with a known loss per foot.
		Antenna co-ax cable is the critical component in antenna system performance that is almost always overlooked and is most likely to be of poor or medium grade when an antenna purchase is made.
	www.smoothtalker.com /faq/cellular_antennas/long.php (1942 words)

	Kids.Net.Au - Encyclopedia > Galileo probe
		Scientific instruments to measure fields and particles, together with the main antenna, the power supply, the propulsion module, most of the computers and control electronics, are mounted on the spinning section.
		The instruments include magnetometer sensors, mounted on an 11-meter (36-foot) boom to minimize interference from the spacecraft; a plasma instrument detecting low-energy charged particles and a plasma-wave detector to study waves generated by the particles; a high-energy particle detector; and a detector of cosmic and Jovian dust.
		Fortunately Galileo had an additional low-gain antenna that was capable of transmitting information back to Earth, but the low-gain antenna's bandwidth was significantly less than the high-gain antenna's would have been; the high-gain antenna was to have transmitted at 134 kilobits per second whereas the low-gain antenna's bandwidth was only 160 bits per second.
	www.kids.net.au /encyclopedia-wiki/ga/Galileo_probe (969 words)

	Mars Exploration Rover Mission: The Mission
		One UHF antenna is on the rover and one is on the petal of the lander to aid in gaining information during the critical landing event.
		The medium-gain antenna on the cruise stage has a waveguide (a pipe) to the rover, that is not used on the surface.
		The low-gain antenna on the cruise stage connects directly to the low-gain antenna on the backshell, which in turn connects to the low-gain antenna on the rover, in a Russian doll sort of design.
	marsrovers.jpl.nasa.gov /mission/comm_xband.html (350 words)

	ESA - Rosetta - Communicating from space: gaining a grip on antennas
		Gain of an antenna system is the increase or ‘amplification’ in signal power, usually expressed in decibels.
		So, a high-gain antenna is particularly good at transmitting signals in a narrow beam whereas a low-gain antenna tends to send its signal in a much wider sweep of directions.
		Although the high-gain antenna is used to return the majority of the data collected, if the spacecraft has to turn even a little, the high-gain signal could miss the Earth.
	www.esa.int /SPECIALS/Rosetta/SEMUT577ESD_0.html (523 words)

	www.cellphoneantennasignal.com 3 Watt Cell Phone Boosters, Antennas and Hands free in car kits
		Antennas with coils, symmetrical horizontal protrusions and other methods are designed for use in places where a metal ground plane is unavailable.
		This type of antenna does not have the benefit of ground plane and transfers the signal by an electrical phenomenon that is called capacitive coupling.
		Note that almost all antennas and the cables that come with them will perform better than a phone in hand, particularly when the phone is used inside of a vehicle.
	www.cellphoneantennasignal.com (2055 words)

	Conformal Array Antenna for Observation Platforms in Low Earth Orbit
		The gain pattern of this fixed beam is shaped to compensate for the distance from the satellite to a ground station.
		The antenna concept, chosen jointly by ESA and the prime contractor, Alcatel Espace, was a semi-active [1] conformal array.
		The antenna needed a large field of view which covered 360 degrees in azimuth and 0 to 62.3 degrees in elevation, matched to a template in which gain was higher at high elevation angles.
	esapub.esrin.esa.it /pff/pffv8n2/polev8n2.htm (906 words)

	Low-gain antenna - Wikipedia, the free encyclopedia
		The low-gain antenna (LGA) is an antenna with a broad radiowave beam width.
		The mountains become the equivalent of rocks in a stream, surrounded by the flowing waves.
		Low gain antennae are often used in spacecraft as a backup to the high-gain antenna, which transmits a much narrower beam and is therefore susceptible to loss of signal.
	en.wikipedia.org /wiki/Low-gain_antenna (116 words)

	Description of Mission
		The high gain antenna is a 1.2 m (1.3 m) parabolic dish antenna mounted on a 2.6 meter boom on the zenith side of the IM.
		The antenna was not operable until it was deployed 22 hours after launch, during which the nadir omni antenna and the zenith omni antenna were used for all the communications.
		Unlike a high gain antenna, a low gain antenna has a low efficiency because the radio signal is transmitted to all directions and the power that reaches a receiver is reduced very much.
	www.tsgc.utexas.edu /spacecraft/topex/instmod.html (1550 words)

	Galileo's Antenna
		The antenna -- a 16-foot mesh paraboloid stretched over 18 umbrella-like ribs -- had been furled and hiding behind a small sunshade for the almost 18 months since launch, in which the spacecraft came closer to the sun than Earth and briefly closer even than Venus.
		The team is confident that nothing is broken and that three adjacent antenna ribs are stuck to the central tower by friction in their paired standoff pins, which are likely misaligned enough that one pin binds the upper side of its socket, its mate the lower.
		Finally, in case the antenna remains stuck, technical teams have been studying a mission design to use the low-gain antenna for Jupiter science return, with atmospheric-probe and remote-sensing information stored on the tape recorder and slowly played back, an option the Project team described at the June 11 press conference.
	www2.jpl.nasa.gov /galileo/anomaly.html (809 words)

	IMAGE DMR
		The sixth instrument, the Radio Plasma Imaging (RPI) instrument, consists of four thin wire radial antennas that are 500 m tip-to-tip and a wire antenna on a fiberglass coilable lattice boom that is a dipole 20 m tip-to-tip.
		Gain (pair): = 0 dBi from 0 degrees to +-70 degrees and +-140 degrees to 180 degrees; and -25 dBi from >+-70 degrees to >+-140 degrees relative to the spacecraft spin-axis, not including interferometer nulls.
		A SPDT RF coaxial switch is used to disconnect the LGA 2 (-Z axis) antenna from the power combiner/splitter during normal operations, thereby eliminating the problem of severe interference nulls on the uplink.
	image.gsfc.nasa.gov /publication/document/dmr/image_dmr_3.html (1737 words)

	From the Satellite to the Ground
		Transmission from satellites is either by a high gain antenna or a low gain antenna.
		High gain antennas have to be pointed in exactly the right direction, but can send a lot of data very quickly.
		The low gain antenna is frequently used when you initially launch, while testing the satellite and waiting to deploy the high gain antenna.
	imagine.gsfc.nasa.gov /docs/sats_n_data/sat_to_grnd.html (1741 words)

	Galileo FAQ - Galileo's Antennas
		The antenna, which is made of gold-plated metal mesh, was stowed behind a sun shield at launch, in order to avoid heat damage from the sun while the spacecraft flew "inside" the earth's orbit.
		Finally, the relay antenna itself would need to be comparable in size to Galileo's original high gain antenna, which would add to the expense and complexity of a relay mission.
		There is a second low-gain antenna on the spacecraft--the long, thin antenna that hangs off of the short boom that holds the radioisotope thermoelectric generators--but it is stowed away permanently.
	www2.jpl.nasa.gov /galileo/faqhga.html (2161 words)

	Weather May Disrupt Receipt of Cassini Signals :: Astrobiology Magazine ::
		If this antenna is stowed during Cassini's Saturn orbit insertion (SOI), flight controllers on Earth will not be able to receive a signal from the spacecraft during the majority of the manuever.
		But before the SOI begins, the high-gain antenna will be turned to point away from Earth, to serve as a protective shield against possible damage by dust particles as Casssini passes through the plane of Saturn's rings.
		The antenna is durable enough to withstand these collisions, but because the spacecraft will be travelling at speeds between 50,000 and 70,000 miles per hour, Cassini's sensitive scientific instruments could be irreparably damaged by slamming into a tiny particle of dust.
	www.astrobio.net /news/article1049.html (980 words)

	Mission to Mars
		So, each rover carries 3 much smaller antennas — one that can move in different directions called the high gain antenna, and two others that are fixed — the low gain and Ultra High Frequency (UHF) antennas.
		When a rover uses the high gain antenna to speak directly with Earth, it is important that Earth be in view of the rover.
		The low gain antenna (remember – this one is used in the first hours of landed operations and as a backup for the high gain antenna), can only handle 40 bits per second.
	www.athena.cornell.edu /kids/bn_special_report.html (1576 words)

	Asa Dotzler - Firefox and more: seven pm update
		Low gain data (40 bits per second, excrutiatingly slow) is incoming now.
		Sounds like the second low gain pass is underway and it could possibly contain imaging data.
		This was based on a simple numeric success code (event record) received from the low gain pass.
	weblogs.mozillazine.org /asa/archives/2004/01/seven_pm_update.html (458 words)

	The Pathfinder Mission to Mars (Site not responding. Last check: 2007-11-03)
		A semaphore signaling the end of this phase may be received via the lander's low-gain antenna.
		The low-gain antenna does not require knowledge of the spacecraft orientation on Mars or active pointing to Earth.
		In this low-gain antenna scenario, this is the end of Sol 1 because no more telemetry would be received.
	www.infoimagination.org /ps/mars/pathfinder_1.html (1982 words)

	Mars Exploration Rover Mission: The Mission
		Spirit's cruise stage switches from its medium-gain antenna (which requires pointing toward Earth), to its low-gain antenna, which does not need to be pointed as precisely for the Deep Space Network antennas to pick up the signal.
		A low-gain antenna on the spacecraft's backshell begins transmitting simple "tones" (sustained radio frequencies coded to report the spacecraft's status).
		The descent UHF (ultra-high frequency) antenna, mounted on the lander, begins transmitting once the lander descends from the backshell, which stays attached to the parachute.
	marsrovers.jpl.nasa.gov /mission/tl_entry1.html (1420 words)

	TVTechnology - RF Technology
		As a result of this difference in antenna patterns, viewers closer to the transmitter site (greater depression angles) may get a better signal from lower-power competitors using low-gain UHF antennas, leaving the high-power station's management wondering why its DTV signal suffers even though the station is operating at full power.
		The antenna was located on a hypothetical tower near the Mount Wilson Post Office with the center of radiation at 1,898.4 m above sea level, 152.4 m above ground.
		Remember, the simplest omnidirectional antenna is a vertical, which requires a vertically polarized signal, either direct from the antenna or reflected and rotated from other objects.
	www.tvtechnology.com /features/On-RF/F_Lung.shtml (1650 words)

	Mars Science Laboratory: The Mission
		The cruise stage has two antennas that are used to communicate with the Earth.
		The low-gain antenna is omni-directional and is used when the spacecraft is near the Earth.
		The medium-gain antenna is a directional antenna that must point toward the Earth for communications, but has more power to communicate when the spacecraft is farther away from the Earth.
	mars.jpl.nasa.gov /msl/mission/comm_xband.html (353 words)

	MoPro Chapter 6.3
		Figure 6-2 shows a plot of the high gain receiver fade versus the low gain fade over the low gain fade interval of 0 to 15 dB.
		Mayer [1996] examined the effects of antenna gains for low elevation angle measurements (8°) at 20 GHz in Alaska through measurement and analysis of transmissions from the Advanced Communications Technology Satellite (ACTS).
		Tracking errors for the higher gain antenna was found to result in substantial fading of the satellite signals vis-à-vis the lower gain antenna.
	www.utexas.edu /research/mopro/chapter06/chapter06-3.htm (474 words)

	Spaceflight Now \| Breaking News \| Minimal data loss expected from SOHO antenna problem
		As expected, communications with the high gain antenna ceased on June 27 as the now-fixed beam slid away from Earth as SOHO orbited a million miles away from the planet at the LaGrange point L1, where the gravity from the Earth and the Sun are equal and effectively cancel each other out.
		The team was still in contact with the 8-year old observatory through its omni-directional low gain antenna, which does not require precise pointing, but also cannot handle the same rate of communications and volume as the high gain antenna.
		Full-time communications with the high gain antenna is expected to be regained on about July 14 after a July 8 maneuver to roll the spacecraft 180 degrees.
	www.spaceflightnow.com /news/n0307/03soho (701 words)

	Final Gallery
		Antennas mounted on the rover allow it to send and receive information.
		Without them we would never receive any images and the scientists would not be able to control the instrument in the rover.
		The low-gain antenna is âomni-directionalâ, meaning it sends and received information in all directions.
	aerospacescholars.jsc.nasa.gov /has/Students/finalGall.cfm?id=661 (743 words)

	Spacecraft Components
		The dish of the antenna was made of strong, lightweight, graphite- epoxy sheets mounted to an aluminum honeycomb for rigidity.
		• The medium-gain antenna (MGA) was cone-shaped structure mounted to the topside of the equipment bus.
		Both these antennas were useful during the malfunctioning of high gain antenna.
	library.thinkquest.org /03oct/02144/text/venus/magel/compon.htm (305 words)

	[No title]
		The Low-Gain Antenna The difference between Galileo sending its data to Earth using the high-gain antenna and the low-gain is like the difference between the concentrated light from a spotlight versus the light emitted diffusely from a bare bulb.
		Two low-gain antennas (one pointed upward or toward the Sun, and one on a deployable arm to point down, both mounted on the spinning section) supported communications during the Earth- Venus-Earth leg of the flight.
		The top-mounted antenna is currently carrying the communications load, including science data and playbacks, in place of the high-gain antenna, and is the basis of the redesigned Jupiter sequences.
	www.astr.ua.edu /galileo/presskit.txt (8203 words)

	Antenna anomaly may affect SOHO scientific data transmission (Site not responding. Last check: 2007-11-03)
		Its low gain antenna, which does not need to be pointed in a specific direction (omni-directional), will be used to control the spacecraft and monitor both spacecraft and instrument health and safety.
		The anomaly in pointing the high-gain antenna was recently discovered when engineers detected a discrepancy between the commanded and measured antenna position.
		To transmit data, the SOHO high-gain antenna must rotate to have the Earth constantly in its field of view as the spacecraft and the Earth progress in their respective orbits.
	www.eurekalert.org /pub_releases/2003-06/esa-aam062403.php (273 words)

	Mariner 8-9
		Also mounted on the top of the frame were two propulsion tanks, the manuever engine, a 1.44 m long low gain antenna mast and a parabolic high gain antenna.
		A scan platform was mounted on the bottom of the frame, on which were attached the mutually bore-sighted science instruments (wide- and narrow-angle TV cameras, infrared radiometer, ultraviolet spectrometer, and infrared interferometer spectrometer).
		Telecommunications were via dual S-band 10 W/20 W transmitters and a single receiver through the high gain parabolic antenna, the medium gain horn antenna, or the low gain omnidirectional antenna.
	www.astronautix.com /craft/marner89.htm (1212 words)

	The Art Of Space
		The array will furnish 2500 W at 100 volts at the beginning of the mission, and less as the spacecraft moves further from the Sun and as the solar cells age.
		Communications are via a high-gain antenna, three low-gain antennas, and a Ka-band antenna, all mounted on top of the spacecraft except one low gain antenna mounted on the bottom.
		A software problem caused the spacecraft to go into a safing mode at approximately 12:00 UT on 28 July, but the problem was solved an the spacecraft returned to normal operations at 18:00 UT. Up to six minor trajectory correction maneuvers were scheduled in the 48 hours prior to the flyby.
	library.thinkquest.org /C0126702/histdeep1.htm (983 words)

	ESA's Venus Express to reach final destination
		The low gain antenna, carrying a feeble but instantly recognisable signal, will be transmitting throughout all VOI manoeuvres.
		So, even with the low gain antenna's signal, it will only be visible during the first half of the burn and the last six minutes.
		The two high gain antennas, located on different sides of the spacecraft, will be used alternately during the mission, to avoid exposure to the sun of critical equipment on the outside.
	www.physorg.com /news63625407.html (1929 words)

	SOHO's antenna anomaly: things are much better than expected
		The interruption was expected due to a recent malfunction in the pointing mechanism of the spacecraft's high-gain antenna (HGA).
		SOHO normally uses this antenna only for low-rate telemetry in emergencies, and the antenna does not need to be repointed.
		Being able to transmit science data through the on-board low-gain antenna using 70- and 34-metre stations therefore means that there will be no hard flout periods for SOHO science data, given sufficient ground station resources.
	www.eurekalert.org /pub_releases/2003-07/esa-saa070303.php (378 words)

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