On top of the center rollbar. Satellite signals will pass through the soft or hard top like they weren't even there. Satellite signals are strictly line of sight and need a full view of the sky.
I don't use one, but the PO put one on the vent in front of the windshield. I don't know how good or bad, but it is a small one that clips on, and I hardly notice it. Some day I will remove it.
My 06 Lj came with a factory radio + sat. XM , the antenna node attached on driver side roll bar where it intersects with over head sound bar. I removed it but thought it was interesting that it even had that option.
Mine is mounted on top of the dash in the right front corner where the windshield and dash meet. No reception problems at all. I also have satellite radio in my daily driver sedan that came OEM as a node/ fin on the rear of the roof like many do. No difference in reception what so ever.