Went to mount my Sirius radio antenna on front hood

I had my XM radio installed by a pro. He ran the antenna wire out through a marker light and them glued it to the roof. I tried to mount it inside the fiberglass cap but had no luck with the signal. The signal also got blocked when on the bottom of the windshield when driving North. Once it was mounted on the roof it worked well. I would try each option to see if works. You have to drive around some to really test it. The roof mount was the last option, but you want to receive a good signal all the time.