It's possible that adding a preamplifier or additional antenna could make things worse, believe it or not. Unless the antenna and/or preamp is also tuned to the desired frequency it will likely increase the level of undesired signals at the input causing all sorts of problems. A scanner or other wideband receiver will behave poorly in a city where there are lots of transmitters for this reason.
I have a shortwaver receiver of moderate quality and I live within 3 miles of a 50kw AM broadcast station. There is a lot of noise or 'junk' from 1.8 mHz up to 7 mHz or so that goes away when I put an AM broadcast filter on the antenna. The stuff that I want to hear comes thru better. Clearly the out-of-band but very powerful signal is gettting thru the front end. A pre-amp could have similar effect in raising the level of an undesired station.
Best to try it and see - then be prepared to take it further if required.