33% should be fine for recording.
Terrestrial will only show a signal if your city has a terrestrial antenna.
(Where are you located)
Check out this page for detailed Sirius antenna setups:
http://www.sirius.com/getsirius/homeantenna
If you are not hearing any audio or getting VU activity try the following:
1) Go into the Levels setting of TimeTrax and make sure all the inputs are correct. (It is the clickable on the main screen that says "Levels")
2) Make sure that on the Configuration screen of TimeTrax the proper recording device is chosen.
3) Go into the Control Panel, then into Sound Devices, click Advanced and check the playback properties and make sure Line-In isn't muted etc.
4) Check the recording properties and make sure Line-In is selected
Follow these steps:
1) Control Panel
2) Sound and Audio Devices
3) Advanced Tab
4) Options
5) Properties
6) Adjust Volume for "Recording" (Click OK)
A new mixer will pop up.... make sure that Line-In is selected.
Click the "X" and see if that helps.
Feel free to open a support ticket if you would like further help.
Derek