wifi antenna

hi all i'm another newbie trying to get my signal 100 yards but there is a house in between i have a linksys router with dd-wrt installed and my problem is i have brought an antenna of ebay they said it was for wifi i plugged it and no change in signal can some1 advise me if i have brought the wrong thing plz it says 49mhz ?
thx brad

49mhz = 49,0000,000 cycles per second

2.4 gHz - wifi frequency - = 2,400,000,000 cycles per second

yes, you bought the wrong antenna

thanks for ur reply... thought i had oh well ya live and learn ehhh back to the drawing board
thx brad