Has the technology changed so much that this will be a waste of time and just flat out needs to be replaced? Is it capable of receiving 800mhz+ at all?
Like others have said, it could work just fine. I don't know if this is considered a discone or not but I have this on my garage that I bought back in the early 70s for my Bearcat III with equally old RG 58/U.
The only BNC compression fittings I have are for RG/6 (too big) so I stripped back the insulation, pushed it in the fitting and taped it so it wouldn't fall out. Seems to work pretty well on both analog and digital with my 996XT.