I've used a wireless lav mic in a 25'x50' lecture hall that is hooked up to a 12 channel Mackie mixer. I've noticed that every time I've used it the pas couple of times there has been an annoying pulsing noise. I believe that it is cell phone interference. The wireless mic is a lower end model $200. I've never had issues any issues with wired mics or a different handheld wireless mic. Are there any solutions to avoiding the interference? I was looking into buying a new wireless combo handheld/ lav but my budget would probably be $600.