Apparently the antenna was not disconnected and the radio was still powered on ? If this is a solid state replacement radio you probably blew a "front end" overload diode or something call a "1st IF ampliflier (a small transistor)". Take the radio out and follow the antenna lead to the first component in the circuit, then test it with a VOM. Radio shack will have every part you need.

Anytime you change an antenna always disconnect the antenna lead and power off the radio.

Good luck.