Move the boombox near a window. The collapsible antennae of boombox radios picks up radio waves that are easily blocked or disrupted by walls and other buildings, especially if they are stone or reinforced masonry. Move the boombox near a window and point the antenna towards an unobstructed piece of the sky.
Wrap the antennae in aluminum foil. This old trick helped UHF television viewers get rid of snowy pictures in the days before digital television and it still does the trick for AM/FM radios. Use the aluminium foil to enlarge and extend the antennae of the boombox to give it more surface to pick up the radio waves. You can even create a forked or T-shaped end to the antenna that gives you a broader angle of reception for the radio waves.
Buy a loop-shaped or "bunny ear" ferrite antenna at an electronics store. These loop-shaped antennae are especially helpful with picking up AM signals, which are higher frequency and often have trouble entering buildings. A looped ferrite-based antenna will actually attract these radio waves and help you pick them up
Turn off as many other electrical devices in the house or building as you can. Other devices, especially Wi-Fi Internet and other transmitting devices, can interfere with the reception of your boombox radio.
Turn the radio to mono. As a last resort, if the station you want to listen to is still fuzzy after you have made other adjustments, turn the stereo sound off and switch to mono.