An average router’s signal will travel:

– 150 ft inside a structure (eg. your home)
– 300 ft outside

Even if you’re living in the centre of a barren, 1,000 foot field (why are you doing that?), still password protect your WiFi (your SSID) using WPA2.

A good password looks like this:
^NKglYA%]tckcM?wG7?r6nFp!

And change your router password, because when was the last time you did.