If you have poor reception after you've hooked up the converter box or the new digital TV you might have an antenna problem. To find the correct antenna for where you live click here http://www.antennaweb.org/. This site uses your address to tell you what type of antenna you need.
You can check the local TV stations' signal strength in your neighborhood by clicking here http://www.dtv.gov/iguide.htm All you have to do is type in your zip code and it will list available TV stations and thier broadcast signal strength.
Check out the DTV help center- http://www.dtv.gov/iguide.htm