I have a tkm mx11 as the comm 2 in my 1975 Mooney m20c ranger. The radio seems to have limited range and usually fails to transmit sometimes after warmed up. Comm 1 is a narco mk12d+ that works surprisingly well for being a narco. Standing back looking at the plane a few days ago it looked like the finish on the rear antenna did not match the rest of the plane. I have the stock 7 antennas. The cork gasket at the base of the radio looked dried up and shriveled so I thought I would remove the antenna and see if it appeared corroded, damaged etc. It was attached with three painted screws and one ground type screw with two star washers on it. The gasket was keeping the entire base of the antenna from contacting the aircraft and underneath the antenna was completely painted. I also have continuity from the center pin of the antenna to the metal base of the antenna. I confirmed the rear antenna is connected to comm2. Can I assume that this installation of this antenna could be part of the problem and the antenna itself may be bad based on the continuity from the center antenna conductor and the antenna base?