Something is generating RF noise that the scanner picks up. You did not say if this only happens at home or if it also occurs when you take the scanner in the car. If it is only at home, you can try turning off power one breaker at a time to see which circuit powers the offending device. Then you should be able to pinpoint the noisy device. If it is something that can be turned off except when you want to use it, that may be a work-around. Otherwise shielding it and keeping it away from the scanner may reduce the problem.