My 2006 had a HD TV but it did not have a digital tuner. I had to get a digital signal from a HD cable box or DVD player. A cheap converter box ($25 at WM) will allow you to get digital signals Over-The-Air but it won't be HD. Your existing antenna will get you some channels if you are close to the transmitting antenna. They make add-ons for your antenna to improve it or you can replace just the head with a better or the Jack head.
2006 HR Scepter 42DSQ
RVIA Certified RV Service Technician