2001 Blazer, radio

I have a simple problem just not the time to mess with it. In short i have a 01 chevy blazer someone installed an after market CD stereo and had no clue what they were doing everything works fine except the radio i know it works due to the fact that if im right next to the local radio station i can pick up a signal but a block away nothing. Thought it might be a break in the wiring but cant seem to find the wire behind the radio to see if it is even plugged in any suggestions what to look for?

either it is the deck just not working properly (like it is packing it in) or you have an antenna problem, either at the back of the deck or somewhere out to the antenna outside the car

check and look around in the pass kick panel.  GM likes to use a ANtenna coupler down there and i have ran into problem with them getting unhook some howWhere theres is a wire there's a way.