Poor radio reception...

[raw6464]

... a grounded antenna? Maybe.

The photo below is the antenna mount and cable connector. Remove the connector A and check that the lower "washer" on the connector is connected to the cables middle conductor and the upper "washer" is connected to the cables shield. It gets grounded from the mounting bracket when the connector is installed... the ground source is from the bracket grounded to the frame. With an ohm meter make sure there is no continuity between the two washers.

If they check out OK there is a possibility the antenna being grounded can be explained if the connector at the antenna base was twisted and installed "upside down". Again, the washer connected to the cables shield should be facing up and contact the mounting bracker when installed.

If when installed the connector was put in upside down you will ground the antenna cable middle conductor and therefore significantly reduce the radios reception. Removing the ground as a fix will improve reception but still won't perform as designed and the radio will be susceptible to interference because the shield ground was removed.