I have a JVC DAB receiver add-on for my head unit which works reasonably
well (apart from questionable DAB coverage but that's another
matter...). It came supplied with an external aerial which can either be
stuck onto the roof and the cable routed down the side of the rear
window or mounted to the side of the boot lid.

Unfortunately it's a hideous looking thing, and I've recently bought a
new car that I don't particularly want to be sticking things to the
bodywork. There is no FM aerial to replace (integrated into rear window)
so I'm left with either options of internal glass-mount or external
glass-mount (similar to car phone aerial but much longer).

What I want to know is, how do these compare in terms of performance?
Most of the areas I drive were fine with the original antenna, with only
a few marginal areas. Is this likely to get worse with a glass-mount?
Bear in mind that my original aerial was about 22cm and all the
glass-mount ones I've seen are 44cm so maybe that gain will help
overcome the other losses.

I'm guessing the exterior glass-mount is the better option compared to
the interior one, any experiences of this?

Finally(!) do all car DAB units use the same antenna connector or will I
need to do some splicing? The JVC one is a really small round push-on coax.

Cheers
Paul.