local studies of an antenna?
114702
Your question is not clear.  Since it is in "networking", it is presumably about antennas for 802.11 wireless or bluetooth, which operates in the same band.\n\nFirst source:  effects of antenna, multipath, etc.\n\n"An antenna simply integrates (or adds up) the various signals directed towards it, with a weighting factor as a function of both propagation and polarization directions.\nDirectionality can change magnitude of multipath effect seen by radio by minimizing contribution of other paths, but does not change radio’s innate ability to handle a given multipath effect.\nDoes interact with circuitry and nearfield environment, changing performance (see 11-04-0675)"\n\nSecond source:\n\n"New world record for unamplified wireless networking!! \n125 miles!"
41398
Concentrate on the antenna -- not the transmitter.\n\nCheck out the homebrew antenna shootout http://www.turnpoint.net/wireless/has.html  This guy made an antenna out of a pringles can that read 87db at 1120'
169706
the angle between the incident ray and the perpendicular to the reflecting or refracting surface at the point of incidence
821395
Please follow the links\nhttp://www.ANTENNA.ORG.UK\nhttp://www.DISH-NETWORK-SATELLITE.NET\nhttp://www.SATELLITE-IMAGE.ORG\nhttp://www.SATELLITE-MAP.ORG\nhttp://www.SATELLITE-PHOTO.ORG\nhttp://www.SATELLITE-TV.ORG.UK\nhttp://www.skwik.com
108576
It has to do with horizontal and vertical lines of magnetic propogation, and it also deals with the way that EMI fields of energy will dissipate from an antanae when a volatage is applied through it.\n\nBasically you will use different shaped antenna to get better RF coverage to certain areas.
450769
go to http://www.radioreference.com/index.php to learn about these channels and why we might need them in cases of arbitrary weather
513722
Check out Radio Shack
31426
Ask about the difference between AM and FM.  Ask about vertical or horizontal orientation of antennas.  Ask for a definition of UHF and VHF.
114950
For resources and information on Frequencies and Handheld Scanners, try the link below.
36159
As mechanical engineer this is out of my normal field but felt you deserved an answer of some sort.\n\n"Because of diffraction effects caused by slits or apertures in optical measurement systems, the radiation energy which is directed towards a particular region on a sample will be spread over a larger area than desirable. By employing an apodizing filter in the radiation path in such system, diffraction tails of the system will be reduced. The apodizing filter preferably has a pattern of alternating high transmittance areas and substantially opaque areas where the locally averaged transmittance function is an apodizing function. In the preferred embodiment, the locally averaged transmittance function varies smoothly and monotonically from the periphery to the center of the filter"\n\nI see the theory here, also found on on using an apodizing mirror to stabalise images in a telescope\n\n"I built and used an apodizing screen for my 6" f/8 scope many years \nago. I made it by layering several layers of window screen, each one \nwith a circular cutout of different diameter. The result was an aperture \nmask with a step-wise approximation to a smooth apodizing function. It \nwas claimed to improve contrast for planetary viewing. Anyway, my \nexperience was that it seemed to make the image more stable but if it \nimproved contrast, I couldn't see it. If you do this on-axis, the \ndownside is that your diagonal mirror will now become more of a factor \nin the contrast equation. The bottom line is I wouldn't recommend it."\n\nAlso "An excellent reference for all sorts of technical techniques is\n>"Procedures in Experimental Physics" (also printed under the title\n>"Physical Laboratory Practice") by John Strong.  I don't recall the\n>publisher, but it came out in the 30's.  The bad news it that it's been\n>out of print for decades (and some SOB stole the copy I got from my\n>father!); the good news is that an outfit called Lindsay is reprinting it\n>in paperback.  (Don't have their name/address here in the office; I'll try\n>to remember to look it up tonight.)\n>\n>                            Dr. Kurt Hillig\n\nEvery ATM should have a copy of this great book. Lots of stuff on\nmirror making, figuring, special laps,making flats, prism ,etc.\nThere is nice modifed Draper machine ( upper disk also powered)\nand a homemade diamond cutting wheel to cut small glass blocks.\n( I would like to build this one someday ) A great section on\nkinematical mechanical construction. Yeah this a mid 30,s book but the \ninfo\nstill can be used. No I don't work for Lindsay Publications,<G>\n\nBob Pfaff\n\n\n This book, in paperback form, can be ordered from\n      http://www.amazon.com, on the Web. It can also be ordered\n      through your local bookstore. Amazon prices it at $23.95, and\n      provides the following information:\n\n      Published by Lindsey Publications\n      Publication date: June 1986\n      ISBN: 0917914562"\n\nSorry couldn't find any really decent expplanations, but at least you've got a starting point.
746511
Dear Sir:\n\nWhile there have been some actual transmissions from Earth to the Solar System seeking echos, and some of this might still be going on in a coordinated fashion, as I understand it, the primary mission of the existing radio telescopes is to "Listen" to upper wavelength radio emissions from gas clouds, and other phenomina in the universe. Of course, once some interesting\nradio emissions are detected, a full spectrum scan of the target is most likely conducted to determine the full extent of radio\nsignals from that source.\n\nOther radio transmissions are made from Earth to our traveling Space Probes and Robotic Explorers at various locations in the Universe. A continual litany of telemetry, television and voice signals also flows between the Space Station and Ground Control Center to keep a constant watch on the health, status, and activities of the space crew, mission, and the station itself.\n\nI will defer to someone from one of those positions for an\nanswer as to the power and frequency of transmissions from Earth to the Space Station, Earth to the Robot Explorers, and Earth to the existing Space Probes way out in deep space.\nMy guess is that these various transmissions take place on frequencies between 2,500 Mhz and 40,000 Mhz. That is a \nvery large radio spectrum. \n\nSince my response turns around your question, in that I am telling you that the biggest radio telescopes listen rather than\ntransmit, let me also tell you that the biggest radio telescopes are not simply single structures at a given location. In recent years a scheme for the linkage of two or more radio telescopes was developed. Therefor, the biggest radio telescope would be an electronic combination of the signals from most of the largest installations on Earth. A lot of work has been done in that vein in recent years. Using more than one receiving antenna provides an easy means for researchers to filter out local ground (earthbound) noise generators and radio disturbances. Signals heard at the same time by widely separated receiving antennas (and equipment) are most probably from the sighted target source (assuming both antennas are aimed at the same target). It is also interesting to know that the radio signals that are received require a vast amount of processing to be identified and detected. The processing of the radio telescope incoming signals takes a huge array of computers and some very complex software programs to yield useable data.\n\nYes, radio waves do go on forever. However, their strength at the point of interception decreases by the square of the distance from the source. So, the strength of radio waves become very, very weak as you move into distances like 100,000,000 miles.\nThe wave front would continue out like rings of water in a pond until they hit something and bounced back off of it. In that sense,\na portion of the radio wave would not go on forever, but would become a new wave moving in the oposite direction from the new source (which was the object that the wave struck). The\nrest of the wave front would continue on until it struck something, and we repeated the above scenario. The exact same thing happens to signals transmitted from a sonar transducer in the water. Those devices are used to detect the depth of the bottom of rivers/oceans (depth finder), fish in the water (fish finder), or even other vessels (sub hunting). Sonar, uses sound waves and not radio waves, but the principle is almost the same.  Sound waves radiate out. Nearby echos are strong enough to be detected with existing equipment and are plotted and displayed on information screens. Some echos are so weak coming back that the existing equipment cannot detect/plot/or display  them.\n\nRegards,\nZah
394259
I heard you need an amplified antenna, so if you are using a regular one, maybe thats why you need to have it near the window.
844222
radio waves..\nand how is this a biology question?
95368
No problem!  A parabola is a parabola.  The distance from the parabola to the focus is the same no matter the wavelength.  Your 3 dB beam width and antenna gain will, however, vary with wavelength.  The antenna gain (EIRP) is given as\n\nGmax = nu(pi D f/c)^2\n\nwhere nu is your antenna efficiency (0.5-0.8 is typical), D is the diameter of the antenna, f is your frequency, and c is the speed of light, 3*10^8 m/s\n\nYour 3 dB width (an approximation) is given by:\n\nTheta = 70(lambda/D) = 70(c/fD)\n\nlambda = wavelength, D = diameter of your dish, c = speed of light, f=frequency\n\nIn order to make this work, you will need multiple feeds, typically appropriate length dipoles tuned for each band, at the focus of the parabola.\n\nMake sense?
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a signal emmited in the band of the 2 GHz.
700634
i heard there are tiny metals ranging in size between\nmicrodots and pieces of wire 1/3rd of an inch.
214904
normally they work with antennas, electromagnetic fields propagation and communications systems. It has to do a lot with electrical signals and electrical behavior of components in the high frequency spectrum (normally above 9MHz, but radio signals of a few KHz might also be of interest)