The Davis VantageVue base station/display "talks" to the remote weather sensors via radio signals (NOT WiFi). My sensors are about 150' from the base station/display unit, and the signals must pass through a stucco outer wall and several sheet rock interior walls. That said, the connection has been rock solid. The WeatherLink is a cable that connects the Davis VantageVue base station/display to a computer, and the computer connects via WiFi over my home LAN, router, and satellite modem to the Internet:
Weather sensors --> base station/display --> WeatherLink --> laptop computer --> LAN --> WiFi router --> satellite modem --> Internet --> WeatherUnderground
I'm using an old MacBook that runs 24/7/365 and WeatherTracker software. The WeatherLink cable has a DB9 serial connector on the laptop end that I plug into a serial to USB converter, and that connects to a USB port on the MacBook. the WeatherLink cable may be available with other interfaces, but you'd have to check with Davis.
Hope this helps...
This is all correct but I do want clarify that the laptop is not needed if you buy the right WeatherLink product. Davis has two products that are both confusingly named WeatherLink, which doesn't make it easy to explain casually.
One of them is what Redneck Geek (apparently my west coast techie cousin

has that plugs into a laptop with software running.
WeatherLink® for Mac OS X, for Vantage Stations by Davis
The other is what I have, its full name is WeatherLink IP (
WeatherLinkIP), it plugs into your Davis Console and connects to your router and uploads data directly without you needing to hook it up to a computer. It can upload directly to weatherunderground as well as to Davis's own hosted site, weatherlink.com, and probably other weather hobbyist sites as well. I have mine uploading to both weatherunderground and weatherlink.com. Davis does not charge to upload to weatherlink.com but weatherunderground keeps better history and stats.
Note that the instructions for weatherlink IP say it has to be plugged into your router. I made mine wireless by plugging it into one of these instead:
Amazon.com: IOGEAR Universal Ethernet to Wi-Fi N Adapter for Home or Office GWU627 (Black): Electronics
So my version of Redneck Geek's diagram is:
Weather sensors --> base station/display with WeatherLink IP dongle --> IOgear wireless adapter --> WiFi router --> Internet --> WeatherUnderground
So it's a bit simpler. But buying the weatherlink IP plus the iogear adapter is more expensive than buying and using the Weatherlink computer adapter and software that Redneck Geek uses. But I like because it's 100% automatic, hands off, no babysitting ever needed, no worries about the computer crashing or going off line. Plus, you're already into it for hundreds of dollars if you're using Davis gear, the percentage difference in cost isn't that much.