How to get better signal?

i have a dell inspiron 600m. i am trying to get a better signal, but i don't know how. when i am outside i am able to connect to an wireless signal called "harper" than only has one bar. i want to be able to connect to this signal in the house but when i go in the house the signal is lost. it will not come up. i have heard about a repeater but i don't know if that will work in my situation,because i don't know where the signal is coming from. will i still bee able to use the repeater for a stronger signal to connect to. are there any antennas i can use to boost my signal for under $50