Test that signal on your local TV to see if it's HD or not. The last few dish receivers only put SD onto the coax so to boost that you seem to know that you have to replace the coax. Once in a while folk just need others to repeat it.
I have Dishnetwork and it splits the signal from one HD receiver to 2 tvs via coax cable in my house. The main tv with the receiver looks great, since it uses the HDMI output of the receiver to the tv, but the 2nd tv looks like crap, even though it is a HDTV, since it sends the signal via coax cable and I have to use the ANT input on the tv. Is there any way to convert at the 2nd tv back to HDMI signal or boost the quality coming off the coax to the hdtv? Tearing out the coax cable throughout all the rooms to replace with hdmi cables is not an option. Thanks for any suggestions!