1. Check your power connections. Make sure that the power cable from your radio is securely connected to the power source. If the connection is loose, it can cause engine noise to be introduced into the audio.
2. Use a noise filter. A noise filter can help to reduce the amount of electrical noise that is picked up by your radio. There are several different types of noise filters available, so you may need to experiment to find the one that works best for your situation.
3. Install a ground strap. A ground strap can help to reduce the amount of electrical noise that is generated by your engine. To install a ground strap, simply connect one end of the strap to the negative terminal of your battery and the other end to a metal part of your vehicle's frame.
4. Move your radio's antenna. If your radio's antenna is too close to the engine, it can pick up electrical noise. Try moving the antenna to a different location, such as the roof of your vehicle or the front bumper.
5. Use a shielded antenna cable. A shielded antenna cable can help to reduce the amount of electrical noise that is picked up by your radio. Shielded antenna cables are available at most electronics stores.
6. Change channels. Some CB radio channels are more susceptible to engine noise than others. Try changing channels to see if you can find a channel that is less affected by noise.
If you have tried all of these tips and you are still experiencing engine noise in your CB radio, you may need to have the radio professionally serviced.