Hi and thank you for using justanswer.
To answer your question;
The resolution 1080,720 etc. is automatically reproduced by the tv set when it receives a signal sent in one of those and it is not adjustable.
On regular(analog) cable ,all the signals are in 480i , only digital cable and /or cable box with programs that are broadcasted in 1080i or p will be shown in those resolution.
And they usually are on pay per view programs/shows.
Now about the ant1 and 2 , i would need your tv`s model number to look into it.
o.k How do you have it connected to your tv ?
Regular coax to the antenna terminal ?
o.k in order to get the HD signal you need to connect your tv and cable box either with component(green/blue/red) YPbPr at the back of your cable box or use a HDMI cable.
Otherwise your tv will only get analog/low resolution signal.
Mitsubishi Sigital TV Model # XXXXX 57734
Cable box Scientific America Explorer 8240 HD
O.k another question;
Do you have a HDMI cable or 5 rca type cables (3for the video and 2 for the audio) ?
I just found the problem- I had the cavle on the DVD and the cable box switched. Thank you!
O.k but the best way will be to use a HDMI cable to connect your tv.
Let me know if you have any questions before(or after)you accept my answer since i found all the documents you need here.