whats the main reason for combining many radio telescopes together into an interferometer w/large distances...
954310
The main reason is to get better results.
614206
Radio has to do with sound waves and LASER has to do with light.  I suppose you could cobble up something using both technologies, but what is the point.  I mean fibre optics and radio signals have little in common other they can be used to transfer information.
645409
Skip distance depends on frequency and the altitude of the Ionosphere for the most part, although other factors come into play. \n\nA simplistic description might be to imagine a mirror in space, shiny side facing the earth. The higher this "mirror", the further apart the transmitter and receiver can be. By the way, multiple "hops" are quite possible.\n\nFrequency and time of day play a great part in the calculation, as various layers in the atmosphere are affected by radiation from the sun, causing them to rise and fall with sunlight (if memory serves, the D layer behaves this way.\n\nCheck out the ARRL for more info (source below)\n\nHope this helps\n\nOuzinki
693154
Only if they are at the same distance from the station and the same atmospheric conditions. The farther the receiver, the longer it takes for the signal to be received.
916623
The observatory's 305-m radio telescope is the largest single-aperture telescope ever to be constructed. (Compare "multiple aperture telescope".) It carries out three major areas of research: radio astronomy, aeronomy (using both the 305-m telescope and the observatory's lidar facility), and radar observations of solar system objects. Usage of the telescope is gained by submitting proposals to an independent board of referees.\n\nThe telescope is visually distinctive and has been used in the filming of two notable motion pictures: as the villain's antenna in the James Bond movie GoldenEye and as itself in the film Contact. The telescope received additional international recognition in 1999 when it began to collect data for the SETI@home project.
167510
Typically, long distance radio waves travel best when there is lots of cloud coverage, and no rain.  (Cell phones, etc are not concidered long range - they are limited to ~32 miles from the nearest cell tower.)  When I speak of long distance, i'm refering to cross country/around the world transmissions.  How is this possible when there is no line of site and the signals don't go through the earth?  It's called ducting.  Read this:\n\n"Atmospheric conditions can greatly affect line-of-sight radiocommunications. Differences in atmospheric temperature or the amount of water in the air can cause radio signals to travel far beyond the usual line-of-sight distance. This condition is called "ducting." At such times, signals travel for many miles beyond the horizon just as though the Earth were flat." (http://www.grc.nasa.gov/WWW/MAEL/ag/agprop2.htm)\n\nTo make it simple, the radio signal leaves the antenna, and goes straight out.  Eventually, due to the curvature of the earth, it "goes up".  If there is a cloud there, the cloud will bounce the signal back down to earth.  Once it hits the earth, it will bounce back up.  This process repeats as long as these conditions meet (clouds).  I've actually heard myself go around the world on amateur (ham) radio.  Weird!\n\nTo learn more, simple do a search for "radio ducting" or "radio bounce clouds ducting" on your favorite search engine.\n\nSorry, if this is unclear, i'm a wee tired and not entirely 100% sober.
650858
sometimes they are used for radio antennas
425955
This line-of-sight technology approach uses invisible beams of light to provide optical bandwidth connections. It's capable of sending up to 1.25 Gbps of data, voice, and video communications simultaneously through the air — enabling fiber-optic connectivity without requiring physical fiber-optic cable. It enables optical communications at the speed of light. And it forms the basis of a new category of products — optical wireless products from LightPointe, the recognized leader in outdoor wireless bridging communications. FSO is a line-of-sight technology that uses invisible beams of light to provide optical bandwidth connections that can send and receive voice, video, and data information.. This optical connectivity doesn't require expensive fiber-optic cable or securing spectrum licenses for radio frequency (RF) solutions. FSO technology requires light. The use of light is a simple concept similar to optical transmissions using fiber-optic cables; the only difference is the medium. Light travels through air faster than it does through glass, so it is fair to classify FSO technology as optical communications at the speed of light.\n\nTypically scenarios for use are:\nLAN-to-LAN connections on campuses at Fast Ethernet or Gigabit Ethernet speeds\nLAN-to-LAN connections in a city\nTo cross a road or other barriers\nSpeedy service delivery of high bandwidth access to fiber networks\nConverged Voice-Data-Connection\nTemporary network installation (for events or other purposes)\nRe-establish high speed connection quickly (Disaster Recovery)\nAs an alternative or upgrade addon to existing wireless technologies.\nAs a safety addon for important fiber connections (redundancy)\nFor communications between spacecraft, including elements of a satellite constellation\nFor interstellar communication
871400
Because up to a few years ago it was always the easiest and cheapest method to transmit and receive broadcasts with.  The first system invented (discovered ?) by Marconi was an analogue system and it has stayed that way since.  \n\nActually, the terms 'analogue' and 'digital' only apply to the modulation methods used;  once the modulated signal leaves the radiating antenna it travels as an analogue electro-magnetic wave through space regardless of which type of modulation is used.
730616
Give this site a look.  And I think everything on it is under $300\n\nhttp://space.about.com/cs/telescopes/tp/tpbegscop300.htm\n\nGood luck.
92830
A type of telescope known as "refractor." Telescopes called "reflectors" are most often used to view distant celestial objects.
1053320
As frequency increases the wavelength decreases and the equipment needed to transmit a certain distance doesn't need to be as strong. This allows the same powered transmitter to transmit a longer distance. This is why radio frequencies can travel a long distance but the output of a loudspeaker cannot.\n\nI think that was the answer you were looking for, since attenuation would be device dependant.
1183464
Sky and Telescope and Night Sky
190587
Refraction bent the light when passing in angle throught glass or other material, it can be use in a optical telescope. But the lens used must become thicker when diameter grow, and that make bigger lens really expensive.\n\nreflection can also be use to build telescope. Big mirror can be build at lower cost than lens.
326080
we have a hubble telescope. its actually a giant satellite that orbits in space. takes pictures. and sends them to computers on earth! neato!\n\nbut an intersting thing is, the pictures we get of other galaxies are what they looked like millions of years ago! thats because it takes millions of years for light to travel from THAT galaxy to THIS galaxy. :)
260642
The hubble space telescope
382985
Light and radio signals are all the same thing, electromagnetic radiation. Radio waves are just very low frequency light and light is just very high frequency radio signals. All objects that are hotter than absolute zero give off some electromagnetic radiation. The really hot objects give off visible light. Cooler ones give off infra red light. Cooler still and you get radio emissions. The Earth's surface gives off radio waves because it is warm. In fact, it gives off so much that it is an interference for communication satellites trying to hear signals from the ground.\n\nModern radio astronomy uses giant antennas to focus radio waves, just like optical telescopes focus visible light. Computers are used to construct images of what the sky would look like if your eyes could see radio waves.