The antenna attached to a car radio must have a good connection for the radio to receive a clear signal. You'll notice problems with the radio if any trouble exists from the antenna to the line leading into the radio. But you can make small fixes to correct the trouble that can range from easy to moderately hard, depending on your level of experience working on cars.
Most cars have antenna lines running underneath the passenger side carpet and into the stereo. Because of this, awkward movements or any other moves that affect the state of the carpet can cause a problem with the connection running from your antenna into your car stereo. If you begin to notice that the FM stereo sounds bad or garbled and you have little or no reception for your AM receiver, chances are you have a loose connection behind the stereo.
It is very hard to get behind a stereo system, so you will have to pull it out. Depending on your car's make and model, this can be a quick job or can take a fair amount of time. Once the stereo is out, make sure all of the wires are correctly in place and that they are all secure. Look at the wiring diagram for the radio in your owner's manual. This can help you make sure everything is properly installed.
If the problem is a loose connection, you can secure it back in place and reinstall the stereo. This type of disconnection is fairly common and most often results from feet moving the carpet.
If you have an aftermarket antenna whose purpose is more for show than functionality, this can be a helpful place to start when thinking about bad reception. Try to install an OEM antenna--original equipment from the manufacturer--and see whether this helps. Often the problem of bad reception can also be traced to having a bad signal from an inoperable car antenna.
