2004 Altima rear defroster interfears with radio

This is most likely a short in the circuit somewhere. Because of the way the defroster is embedded it may not be repairable if the problem is the defroster itself however, it is possible the problem is actually in the Antennea connection to the radio. Double check that connection first. If it is solid and good I recommend you get a Haynes repair manual on your vehicle to get troubleshooting steps for the defroster.