Best wireless antennas for better range?

Can anyone recommend a decent wireless antenna? I need my laptop to pick up more networks... maybe something from Alpha M or just some shop in a city like Chicago or something... looking for something that isn't dirt cheap, but also won't break the bank. Just nothing low-quality... ideally, I want an antenna where it clearly states the range for 6GHz and stuff like that. Also, if I'm using an old laptop from 2004, like an Acer TravelMate 2490, what kind of GHz frequencies can it even catch? Sorry if I have the wrong info in this PDF I'm looking at, and sorry if this topic is out of place... I just really need some answers to these questions!

p.s. I'm running Windows Mint, if that matters at all

Wait, where exactly are you planning to plug that antenna in? Which connector are you even using?

The connector? I'm a bit lost here... not really sure which one would be the best choice for this...

The 6 GHz band is just a frequency—it doesn't actually dictate how far the signal reaches.
As Michael Jackson10 pointed out, how are you planning on hooking up your antenna?
What kind of wireless adapter are we talking about here? Is it one of those built-in ones, or are you using an external USB dongle?

You probably should've asked that here
http://forum.pcekspert.com/forumdisplay.php?f=16

There isn't really a simple answer. I don't think there's actually a laptop out there where you can just plug in an external antenna
At the very least, you'd probably need a USB Wi-Fi adapter with an antenna on a cable