TV
Just to be sure - are you wanting to watch TV on your computer, or output to a Tv or capture TV or video?
A separate TV card (eg Hauppauge or Pinnacle) in your PC should give reasonable picture quality, comparably to a TV using the same aerial - but in a resizable window which can be displayed while you work. If you want great picture quality it may be worth getting a digital TV card (either terrestrial or satellite) - I think a Hauppauge Win TV Nova-t will be my next toy!
(PS - you'd need to check your digital reception in your area)