|Having two directional antennas, one at each end, would work nicely to provide a strong wireless signal to the distant computer. I would however use a SOHO router at the far end to attach the second antenna to, not your laptop. This way, should you require it, you could extend the network to that location and have more than just the one computer connecting to the network. A SOHO router that has 4 LAN ports and is wireless capable would allow you to connect multiple clients either wired, or wirelessly.|
I've had good luck with EnGenius brand equipment. It's mid-grade, not too expensive, easy enough to use if you're reasonably computer literate and I'm sure you could find something that would bridge a distance of 420 feet.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.