bucheron

hi excuse my english i want install sirius radio on my venture 2005 and more people on this forum said i install 6 volt supply why 6 volt ?i d'ont understand sirius is 12 volt? and i want to know if i can plug directly my radio in the plud of lighter on the fairing. And the antenna where you put on the bik,e not inside the fairing thanq you for your answer and excuse my english not good bucheron