Would like to communicate between an Arduino and a PC but over a distance of 2500+ feet outside in the open, wirelessly. What would be the best way of doing this? The communcation devices I have found (xbee,...) dont go the distance.
What sort of data rate do you need to maintain?
Long range communication is quite possible in open areas with very low power - a project I am currently working on incorporates data transmission over 500 KM using only 25 mW (miliwatts) of tx power - this of course relies on a line of sight, and data transmission is at only 50 baud. Even without line of sight, omnidirectional communications outdoors are quite easily achievable over the range you're looking for.
As others have mentioned, matching your antennas with your intend usage patterns is important - can you give us more detail as to requirements/use patterns?
One factor your options depend on is how the data transfer rate you need over that distance. More of the long range, low power applications reduce in throughput as the distance increases.
For example, the XBee Pro 50mW Series 2.5 operates at 2.4GHz with a range of 1 mile and has a data transfer rate of 250kbps.
The longer range XBee Pro 900 XSC operates at 900MHz and has a range of over 15 miles, but a data transfer rate of only 9.6kbps.
You could also look into directional antennas and signal amplifiers.
Wifi maybe if you used range extenders for your network, or if you have the funds you can use the cell network with a module like these from sparkfun.
There are XBees that communicate about 1 mile (~4800 feet?). http://www.ladyada.net/make/xbee/modules.html Maybe you can even improve the range with a better antenna.
As was mentioned the XBee with the 50mW antenna should do this. You want to make sure you order the high gain antenna. There is a series of XBees that come with a coax connecter on the top. IIRC the highest gain antenna is the whip antenna with the coax cable. The document that discusses the antenna gains is application note XST-AN019a from MaxStream.
We have successfully pushed this communication more than a mile on our miniature UAVs without ever coming close to loosing communication. It is a serial modem our buadrate at this time was 9600.
good luck !
You could use standard Wifi 2.4Ghz or 5GHz radio units with panel, yagi, or parabolic directional antennas. Use an Ethernet shield on your arduino and the ethernet port on the computer (or your network). This distance is completely achievable with this type of setup, and supports high bandwidth. I have used enGenius and Deliberant brands with no issues over such distances.
For a cheaper solution, you may be able to achieve this with a couple of standard wifi routers like the linksys WRT54GL running DD-WRT or other firmware which allows customization of the ACK timeout, and by using some small directional antennas such as this, or at l-com.com check out their selection of 2.4GHz antennas with TNC connectors.
I remember a 100 mile link in South America that was reliable with 100 mw on at 14 MHz with a buad rate of of 2 or 4 using a extremely stable oscillator and very narrow filter all built with analog parts.
I should be easy today if you can get a frequency from 3 to !50 MHz. A GPS can be use to synthesize as good a clock as you can find and modern digital signal encoding and decoding messages that can pull signal you can't hear in solid copy. If you put a narrow filter over a stable frequency an amazing amount of noise can be filtered out. The using a phase shift decoding the computer can pull out things I can't see or hear.
Of course the more narrow the filter the lower the baud rate.
In the US and Europe access to frequencies for data radios is difficult to impossible. If you want anything that approaches prompt data access you need 3 to 5 bands scatter over the range from 3 to 30 MHz and their not sure every day. The frequency range of 50 to 150 MHz is relible from 3:00 AM until noon as meteor scatter. It needs at lest a 100 watt radio with an antenna gain 9 dBi. It has been done with and ERP of 100 watts but connections corrode and parts age so you need a safety factor.
It's been 10 years since I worked in Central, South America, Mexico or Africa. Their frequency allocation at the time were much more flexible. Working as contractor I told my client what I could find out about the law and left it up to him. You can make a great 7 MHz NVIS antenna on a Caboose or over the boiler of engine on a train that will give almost constant location of a train in Africa for 500 miles. Double back on its self and does well on 3.5 MHz at night.