Ambitious RF project, HELP!!!

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chessman
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Ambitious RF project, HELP!!!

Post by chessman » Thu Feb 20, 2003 9:50 pm

I would like to create a radio modem system that can give computer data speeds of a 56k and up at a range of 50 miles. HELP!!!<p>Eventually, I would like to be able to create a network of these devices.

bodgy
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Re: Ambitious RF project, HELP!!!

Post by bodgy » Fri Feb 21, 2003 1:50 am

I don't know the FCC rules, but wouldn't you need an amateur licence for that sort of power?<p>Colin
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jollyrgr
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Re: Ambitious RF project, HELP!!!

Post by jollyrgr » Fri Feb 21, 2003 6:43 am

About the only thing I know of is satellite connections. You would need two or more satellite dishes and modems and the related service contract. An example of two way satellite is StarBand. See the web site at:
http://www.starband.com/<p>A few points:<p>Amateur radio modems are just getting into the 56K data rates. But you need a repeater to transmit the UHF or Microwave signals over the distances you want. VHF and above frequencies are, for the most part, line of site. (Yes, I am aware of tropoducting but this is not a reliable/steady option.) Thus you need a repeater with an antenna located at a high elevation. Amateur signals cannot be commercial or encrypted. Something you are probably wanting with computer data transmissions. Commercial FM stations transmit at several thousand watts and have high towers and rarely get these distances.<p>
This type of network DID exist for amateur radio operators in the Atlanta area, and probably in many other areas. But cheap high speed DSL and cable modems have replaced these types of networks. Go here for an example:<p>http://www.wa4dsy.net/<p>If you want point to point 56K at 50 miles you are asking quite a lot.
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chessman
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Re: Ambitious RF project, HELP!!!

Post by chessman » Fri Feb 21, 2003 9:18 am

Then what about 10 miles? Why is it not possible to just use the 50MHz band? I assume at that frequency, the transmission could be omni-directional. There would be a slight amount of dropped packets, but software could get around that, right?

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Re: Ambitious RF project, HELP!!!

Post by vapor » Fri Feb 21, 2003 5:13 pm

Try reading information on Packet Radio in the Amateur bands. But remember, you MUST have a License to utilize the Amateur Radio spectrum and it cannot be for business and it cannot be profane.<p>With the right type of equipment, 50 miles is no sweat, but the 56 K speed is another issue.<p>In a nut shell, at both ends you will need a tower (say 50 to 75 foot should work), an antenna tuned to the proper band, a transciever (depending on the band you select, it will need to have sufficient power), a T erminal Node Connection (TNC), a computer and appropriate application software.<p>I do not believe you want to use the 50 MHZ band for your project unless you want to earn the WATV Award! (Work All TV's!)<p>
For point-to-point communications, you should try the higher Amateur frequencies (if properly licensed) in the 1.2 Gig or higher range. These frequencies are ideal for what you are trying to do.<p>If you are not licensed, then find a local ham club in your area (do a net search on Amateur or Ham Radio +your city). They can probably put you in contact with a V.E. who can lead you on the path to get your license. You'll be suprized, it has become relative easy to get licensed now days.<p>Good look!
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Chris Smith
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Re: Ambitious RF project, HELP!!!

Post by Chris Smith » Fri Feb 21, 2003 6:11 pm

I believe HAM radio has it already?

chessman
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Re: Ambitious RF project, HELP!!!

Post by chessman » Fri Feb 21, 2003 9:36 pm

My cell phone can only do speeds of 9.2Kbps.<p>Is it possible to use current GPRS cell-network systems? Probably not....but it's a thought.<p>I'll try the local HAM society, and unfortunately, it sounds like this will not be a reality in my area, as I cannot set up a directional antenna, or any large antenna in my neighborhood.<p>Thanks for the replies.

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