First off, I'd really like to thank all of you for your patience and help.
I think I may have found a solution, if not the cause.
I was testing stuff last night and was holding the antenna out the window. Getting good reception, I shifted it in my hand and my fingers covered it for a moment. At that moment I saw all the satellite bars drop. Can this thing be that sensitive?!
Now, the reason I was struggling with this was because the carputer WAS getting signal but it would decrease with time. Seems odd that it would be antenna placement with it working like that. And again, with the antenna in the same position the laptop worked better.
What I didn't take into account was to hook up the laptop I had to remove the carputer screen from the dash. That must have been just enough to cause it to start working. I was thinking primarily about stuff covering the antenna causing the problem.
The antenna was to the left of the carputer and display under the dash. Last night when moved it to the corner of the dash it got great reception.
So I removed the glove box and moved the antenna to the very front corner under a speaker grill. I'm now getting great reception. Time will tell if it decreases like before, but for now everything's working.
I'm somewhat embarrassed that it might turn out to be something so simple. But with it working and slowly not working it just didn't seem to be a placement problem.
Thanks again for helping with this.
It was in your dash?
If that was the case being in-sight with the sky is going to be way better.
I tried in house and didn't get much. Put in on my dash and bingo!
GMPC works fine with the BU-353 ...
Good work, Dave. Humans cannot see RF waves, so it is not easy to ID these issues sometimes. Congrats on fixing it.
It's better to put the CarPC in a metal case to avoid RF interference causing disturbance to other components....
My thinking was the dash is plastic. Plastic is invisible to RF, right? The antenna was to the left of the PC by about 6". Under the dash just above the instrument cluster. Some of the times when I was testing I'd place it in the same position but on top of the dash.
Now it's still under dash plastic but away from the PC. It seems to be working great right now. I just pulled it out to prepare for the new radio and joycon.
the screen you had to pull out creates a lot of rf noise because of the ballast for the backlight lamp. ive noticed this is the worst emitter of interference in my car (lilliput eby701). so when you take this out of the equation i can see why it helps.
also, being under the dash, even though its plastic, is still closer to interference then it would be on top. but if its working and stays working, then its all good of course.
I'm pretty sure I've got led's for backlight. According to the description on MOCOSO it should.
Either way it probably does make noise.
I just wish it hadn't worked from the start. With it working at first I didn't think of moving it.