only way to open the hd channels is to have a hd box,you maybe able to improve the picture from sd to 720 but you still cant view the likes of bbchd,bbc1hd,itv1hd etc,i have also found by using a good coaxial cable [ not 20 years old ] and tight connectors and i also use a powercleaner type surge protection to improve the picture,or i did when i had the cable.;)