The Poseidon radar transmitter is a radar component that the Sole Survivor is tasked to retrieve as part of the quest Last Voyage of the U.S.S. Constitution. It is used to repair the ship's radar transmitter as part of the quest.
Poseidon radar transmitter (1)
There are 2 available locations Mr. Navigator might send the player to recover the radar transmitter:
While the Poseidon radar transmitter has material types assigned to it, it cannot be scrapped, due to it being a quest item (and it remains a quest item even after the quest has been completed).
PC This item can become stuck in the player's inventory if the option to Jury-Rig a fix for the Radar is chosen, as it is considered a quest item and cannot be dropped or placed into a container. This will occur even if the item is obtained after the quest has been completed, so it is advised to not pick it up if the Jury-Rig option is used. Can be removed from the inventory by using the console command player.removeitem 0009139e.