Looking at a picture in the brochure for the radio, it shows the front cover removed and the antenna connection is through the back of the chassis which is solid aluminum. Sorry I can't provide a more concrete response to the original question.
I just picked up a VX-6R the other day, primarily for the extended receive. As previously mentioned, it's almost the same cost as the scanners made by the hammie companies.
The connector is hidden by a rubber gasket and I haven't had a look under it, it didn't want to just pop right off. FWIW I ...