On Saturday 05 March 2011 20:13:34 Kussh Singh wrote: > You have to create a long distance link with a directional antenna > a > > > tincan /pringle antenna is easy to do and has 100s of > > installations. on one end you connect your wifi router to a > > regular adsl or other internet connection. At the remote end you > > terminate into a lan network. > > > > How much distance is meant by long distance? I suppose the > > distance would > > be inversely proportional to the square of the transmitter's power.
It depends on EIRP. Which means an omni antenna which radiates 360 steradians works only for short distances. Links upto 20 Km are operational in installations with both antenna on hilltops. 8 to 10 km LOS would be a safe bet. > > The link will work only line of site, so you need both antenna as > high > > > as possible. > > > > How high should the antenna be? The Reliance provider says he has > > 80m high > > towers with a range of 15km but we are just 4 km away from that > transmitting tower as the crow flies according to him. And then he > says we need a tower at our site also which will be provided by him > and will be either 18m or 27m high. I fail to understand --on one > hand he says his transmitting tower has a range of 15km radius and > on the other he needs another tower at the client end of about 27m > in height which is just 4 km away. You have to be LOS. If there is some obstruction in between (like trees, or buildings) you have to go above that. Also ISPs use omni directional, not directional, so their equipment is far more expensive > The frequencies (RF or > microwave) used or licensed to Reliance are not mentioned--if > anybody knows of any link to TRAI or DOT websites which could shed > some light on the matter, it would be most helpful. 5.4 Ghz afair > Since the > frequencies will determine whether we would necessarily need line > of sight or could work even with non line of sight. The > frequencies licensed to Reliance would also determine whether we > can easily recieve the 2 Mbps speed or there will be significant > attenuation. ALL wifi requires LOS the operate above 2.4 GHz. The speed is actually capped. But you will get around 4Mbps for long distances with an 802.11G > > Also there must be some frequency bands which are still unlicensed > or free to the Indian public for putting up their own wireless > meshes or wimax etc installations??? open meshes are banned. Public use is the wifi band. Although in principle you are not allowed to transmit more than 100Mtrs, I doubt there should be any problem with a school, apart from the departments not having any equipment to check anything worthwhile even in cities. > > Also i have been told that the router being given by reliance in > their quotation is almost obsolete and will need to be upgraded to > an ethernet router when we go in for speeds higher than 2 Mbps > later. So can anybody give me an idea of the hardware equipment to > be thought about and the costs involved? > > > Thanks in Advance for any help. > > Kussh -- Rgds JTD -- http://mm.glug-bom.org/mailman/listinfo/linuxers
