Dude, I am totally intrigued with this! I designed communications systems for years and this is a new one on me. Your system should operate on 315 Mhz if you are in the US. But not your garage door. The supervisory signals are on a subcarrier and would normally be disrupted with the main signal. Could be a harmonic but i don't think so. Check the jam detect on the simon in all three modes and see what you get. try it on the battery only and see what you get. do you have a keyfob? what is it's range? My best guess at this point would be a new digital tv transponder that doesn't have a splatter shield or one that is not working. I'll stay with you on this, let me know!
Hmmmmmm, Interesting, what error codes do you get? Is it showing not detected or is it a supervisory communications error? Do you have overhead power lines outside? Does your garage door do funky things? How is the range on your 6.0? Lots of investigating to do here!