Guys: Thanks a million. Your posts spurred me to sit up on the rack and take a GOOD look. The faring and horizontal support covering the antenna are thick plastic (insulation, I believe). The antenna is also blocked from the sky at various angles by the heavy bars of the rack and the PIAA lights. It's a miracle we are getting any sound at all.
I came to the conclusion that relocating the antenna ahead of the faring is the answer. The thread Rodster referred me to definitely confirmed my thinking. I'm going to leave the old antenna in place because it seals up the roof. My installer is a body shop that does insurance repair work. I'll ask him to order another OEM Onstar antenna and locate it ahead of the faring.
All things considered, I'm happy with the GOBI rack. It is very strong. I was out driving at 75 mph today with no appreciable wind noise. Installing a new XM antenna ahead of the faring is just a cost of the overall rack/lights project.
I'll put up a post with the results from the new antenna installation for anyone who is interestes.
Thanks again for helping me get to the bottom of this. No doubt about it. This is the best source of H2 information.
George SSSS
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Black 2005 Adventure Series; factory touch screen GPS w/XM radio; factory express open/close sunroof; reclining second row seats; Warn 9.5ti Multi-Mount Winch; Gobi Stealth roof rack with PIAA lights; HotShot windshield washer fluid system
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