If you subscribe to Premium TV services, chances are you have no clear frequencies to allow a clean and clear broadcast of your personal channel. You can tell by tuning any channel between 65 and 80 and looking at the TV. If you see a signal, noise or snow, then a notch filter is needed. It deletes channels to make room for your personal Avcast channels. The notch filter you select will block a range of 5 channels in standard TV broadcasting. If you have any kind of Digital TV broadcasts, then you will likely clear more channels, typically the one above and one below of the filter range you order.