A smart-arse answer would be to keep using your old antenna, but you need something better than that.
A 2.4Ghz vertical omnidirectional antenna with 16 DB gain would probably be in the neighborhood of 9 feet tall. It would be a collinear type antenna. You were taken. The one you bought might deliver 2.5db in real gain. A simple rule for buying anything on Ebay is to know what you are buying. If the price is too good to be true- then it probably isn't true.
A small corner reflector would have been better. A good one (HERE) is available at Fry's and other places. The thing actually works as advertised.