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An antenna (or aerial) is a transducer designed to transmit or receive electromagnetic waves. In other words, antennas convert electromagnetic waves into electrical currents and vice versa. Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, wireless LAN, radar, and space exploration. Antennas are most commonly employed in air or outer space, but can also be operated under water or even through soil and rock at certain frequencies for short distances. Physically, an antenna is an arrangement of conductors that generate a radiating electromagnetic field in response to an applied alternating voltage and the associated alternating electric current, or can be placed in an electromagnetic field so that the field will induce an alternating current in the antenna and a voltage between its terminals. Some antenna devices (parabolic antenna, horn antenna) just adapt the free space to another type of antenna. Antennas were used in 1888 by Heinrich Hertz (1857-1894) to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed the emitter dipole in the focal point of a parabolic reflector. He published his work and installation drawings in Annalen der Physik und Chemie (vol. 36, 1889). From Wikipedia under the
GNU Free Documentation License  vansairforce.net 600px x 800px | 162.70kB [source page] Here s a nice pic of the towers for Dallas and surrounding areas They are south of Dallas about 20 miles in Cedar Hill http www vansairforce net TEX Cedar Hill Antennas jpg Don t know the exact height but they are in the 1000 range From Yahoo Image Search: "Antennas"  kc8qvo.com Steve Fri, 07 Aug 2009 19:18:00 GM They do have some good . antennas. . I have three Cushcraft . antennas. myself - an A270-10s, A50-5s, and a 13B2. They aren't the best . antennas. , but they are good. MFJ does has several nicknames, based on a following of bad quality checks and ...  3gstore.com unknown Sun, 10 Sep 2006 14:22:18 GM 3Gstore.com : Which . Antenna. is Best for Me? - Misc. Sprint Mobile Broadband 3G Routers Adapter Cables Amplifiers / Repeaters Network Adapters Yagi / Directional . Antennas. Extension Cables Refurbished Sprint Phones/PDAs ROUTERS select ...  dxzone.com The DXZone.com Sun, 02 Aug 2009 06:55:51 GM Another Approach to Active . Antennas. . ... Active . antenna. with a frequency response that is flat from 5kHz to over 30MHz. . Antennas. /Receiving. Listed on Dxzone.com since 2009-07-31. Hits : 69 - Rating : 0.00 - Votes : 0 ... From Google Blog Search: "Antennas"  news.google.com PR Web (press release) (press release) For a limited time, espymall is offering manufacturer direct outdoor HDTV antennas that are on sale for $58 plus free shipping. ... and more » news.google.com Electronista Boomboxes with radios, as well as accessory kits with antennas , are also considered possibilities. A satellite radio adapter for the iPhone would further ... and more » news.google.com Eagle Tribune MetroPCS is the same wireless carrier that is placing six cell antennas in the steeple of Trinitarian Congregational Church on Elm Street a move that has ... and more » From Google News Search: "Antennas" Why do the black ants in my house rub their antennas? Q. You see whenever I'm around them, they rub their antennas and if i make loud noises such as stomping they rub it. Why is that? Asked by Anonymous - Tue Mar 25 10:30:44 2008 - - 3 Answers - 0 Comments A. so that u can tune ur antena to their frequency Answered by saharaaj - Tue Mar 25 10:52:26 2008 Reasonable radio antennas range from1 centimeter to5 meters in diameter. What frequency range does this cover? Q. Radio antenna often work best when the diameter of the antenna is equal to the wavelength of the radio wave. Reasonable antennas range from 1 centimeter to 5 meters in diameter. What frequency range does this cover? Asked by digitaldocuments - Sat Nov 3 04:46:59 2007 - - 3 Answers - 0 Comments A. ignoring antenna question, let's do frequency given the wavelength: [speed of light] c = freq*wavelength freq = c / w 1cm: freq = (3*10^10 cm/s) / 1 cm freq = 3 * 10 ^10 Hz 5m: freq = (3*10^8 m/s) / 5 m freq = 0.6 * 10^ 8 Hz freq = 6 * 10 ^7 Hz NOTE: 3*10^8 m/s = 3*10^10 cm/s NOTE2: 1 Hz = 1/sec I will leave the assumption about the relationship between antenna length and wavelength alone, since I disagree with what you say /*** just an aside ***/ if it was "me", I'd multiply those freq's by a factor of "4" reasoning follows: antenna-length is *also* sometimes regarded as = wavelength / 4 for (quarter wavelength monopole) citing:\ The most basic antenna is called "a quarter wave vertical", it is a quarter wavelength long… [cont.] Answered by athiestforthebirthofjesus - Sat Nov 3 04:56:23 2007 are there any tricks for cb radio antennas?
Q. I recently put a cb radio in my truck. When me and a friend of mine tested it out he couldn't hear me and I could BARELY hear him. We were less than a mile away. Is there anything I can do to my antennas to fix my problem? Foil or anything like that? Asked by mike_tbpmerchbeast - Tue Feb 3 17:15:38 2009 - - 1 Answers - 0 Comments A. You need to have the SWR set on the antenna. SWR stands for "Standing Wave Reflection" and relates to the amount of reflection your transmission gets off the body of the vehicle back into the antenna. You'll need an SWR meter, some CB's have them built in, to set the antenna. The procedures for setting it will vary depending on the type of antenna. Once you have an SWR meter, let me know what type of antenna you have and where it's mounted and I can explain further. If you get a seperate SWR meter not built into the radio you will also need a short 3 ft ant cable to connect it inline with the antenna cable at the back of the radio. Continueing to use the CB or trying foil will result in damage to the CB so don't...until the SWR is set. Answered by tcbassist - Tue Feb 3 17:32:54 2009 From Yahoo Answer Search: "Antennas" |
