I feel certain that the signal would be lost in tunnels unless in range of a terestrial repeater for the same reason.

When in the woods under heavy foilage the signal got somewhat intermittent, but that is a problem you are going to experience with any satelite radio due to the extremely weak signal strengths involved.

I also got the home kit, but the signal is EXTREMELY choppy in doors.

If you live in an area with a lot of trees, getting a consistent signal will almost be impossible

There is an "FM out" jack on the left side, and I looked everywhere for an accessory antenna to help boost the FM signal

Other things I didn't like about this:Easily Obstructed Signal

The signal gradually grew worse before it died

Newer units broadcast much weaker signals

Same complaints as others: love the content hate the hardware, trouble maintaining signal, runs hot, FM modulator is weak etc

If you drive near any trees or under bridges you will lose the signal

When the unit gets hot, it loses the signal.

If you live in an area with a lot of trees, getting a consistent signal will almost be impossible

I didn't even need the manual)Right away my signal was clear as a bell once again

I was hoping that I could just toss it on the dash so that I could move the radio between cars, but that made for a very choppy signal

Going under ANY hwy overpass or even a small tree will drop the signal and annoy the heck out of you.