Of course, these are extreme examples, detecting the slightest bit of signal, amplified over long distances, using after-market antennas to focus output power. Typical wireless APs (or routers) with factory-installed antennas are lucky to deliver data a usable rates at open space distances up to 300 feet. Indoor/obstructed reach can be much less.
To connect your routers at 750 feet (depending upon obstructions), you will probably need amplifiers and/or directional antennas. Check out this tip to for a quick primer on Wi-Fi antennas, or this in-depth how-to on boosting WLAN performance. You'll find some low-cost "range extenders" on the market, but anecdotal experiences vary -- for example, read diverse opinions about the Linksys WRE54G posted at Tom's Networking.
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