1 What could be the ideal location for installing Car radio antenna?
2 Can there be advantages of fixing more than one Car radio antenna?
The best location is the center of the roof panel. But this is often not convenient so alternate, but not as effective, locations are often used. These include the center of the trunk lid or on top of the fender.
There can be but it can be difficult to properly balance more than one antenna. If you know what you're doing and have access to proper equipment, you may have success with this.