Electrical Bonding for an exterior building
You need a ground wire and ground rods at both structures

You are correct that you only bond neutral to ground at the service entrance.  However, current Code not only calls for a grounding wire between the structures (which you have provided), but for a grounding electrode system at both buildings.  This can be a concrete-encased electrode (if provided), or the old saw of two 8' ground rods driven 8' apart and connected with an appropriate-gauge wire if no better electrode (such as a concrete-encased electrode, foundation steel of some other sort, or a well casing) exists.

Each grounding electrode system gets a grounding electrode conductor back to the ground bar in the panel/disconnect for the associated structure, and the feeder equipment grounding conductor in the inter-building feeder connects the two together, from ground bar to ground bar.

You are also correct that the radio tower needs a ground rod, and that its ground needs to be bonded to the mains grounding system at the structure where the radio device (transmitter or receiver) is located.  This ground wire goes to a tap on the structure's grounding electrode conductor, made using an intersystem bonding termination device or suitable tap connector.