It's not so much about a 'bigger' antenna, but one designed for the band you are listening to the most. Whatever you have the hardest time listening to, then get an exterior antenna for that band. Other strong signals should still be OK usually. The so-called 'wide-band' antennas, will sometimes make things worse, not better... because they will pickup so many signals, you can have interference issues. But yes, the 'picket fence' thing can still happen sometimes, no matter what.