Considering that gpsapp is only passively listening to the serial port in NMEA mode. Your receiver must be always on as long as it receives power through the jack.

I had the same 'I wonder if it really works' feeling when I connected the SV6. And it is one of the reasons why I added the signal strength display in the first place. Most things I write is to 'scratch an itch', if it bugs me enough I fix it.

The difference between hollow/dim and solid/bright right now is that the solid bars are the satellites used for the location fix, the others are either to weak or intermittend or just have an unlucky position in the sky so they can't add anything to the triangulation or something.

However, things keep changing and ITNR the bright vs. dim color will indicate whether we received a measument for that satellite within the last 2 seconds. I.e. you could have bright/hollow bars for satellites that are still received promptly but probably are not in the solution because they are too close to the horizon, or too weak. And dim/hollow bars for satellites that are currently obscured, and possibly even dim/solid bars for satellites that were used for the last solution, but are currently obscured (when we drive into a tunnel?)