Four feet sounds wrong. Is it vertical or horizontal? A simple quarter-wave vertical antenna would be about 2 feet long. If you use a longer aerial which is not properly matched the receiver will not unction correctly.
The PSR-282 is a very basic wideband receiver which is probably designed to work just with the "rubber duck" aerial provided. If you use a larger aerial at a place which is full of RF (eg Heathrow) the receiver will almost certainly be blocked by all the transmissions.
Lastly, keep in mind the legal aspects of your activities.