outdoor antennas are the only ones that work, screen windows and portable phones and wifi (any radio noise) will affect the performance of them drastically, the only way to reliable get HD over the air is to go outdoors, pretty much any outdoor antenna works, just some workbetter then otehrs, if you have lots of trees around your area you better get the mast above the trees, with HD over the air its a digital signal and as such is ALL or nothing signal quality so you either get it perfect or not at all