How do you stop the antenna extension noise on a car radio?

To stop the antenna extension noise on a car radio, first ensure that the antenna is securely connected and not loose. You can apply some lubricating grease or a rubber washer to the antenna joint to minimize vibrations. Additionally, checking for any physical damage or wear on the antenna itself may help, as replacing a faulty antenna can also resolve noise issues. If the problem persists, consider adding a noise filter to the radio's power supply.