Sound system fuse blows
 

Just bought a 1995 convertible and radio keeps blowing fuse sometimes right away and others 10 minutes later. Radio clock and CD ejection etc works after fuse blown but sound and antenna shuts off. When I purchased car antenna didn't work and previous owner gave me a new aftermarket antenna that came with car but had no instructions. Installed it everything worked until car is started then it blew a 20amp fuse in main fuse block under hood that didn't blow until new antenna installed.. I did notice a wire that was grounded with 3 others at the original antenna that was cut off. The wire is the 1 that goes up around and at top of rear drivers side fender well that is cut and there is no sign of other end of wire. May be the problem anyone know what that ground is to be connected to. Any help would be greatly appreciated.