It is used to construct the signal interceptor in combination with the beam emitter, the control console and the reflector platform in the quest The Molecular Level, that allows the Sole Survivor to travel directly to the Institute. Each of these items will disappear from the workshop after being used.
Relay dish (1)
Once the player character has powered up the radar, any contact made between the player character and the teleporter will stop all movement and after a quick dialog will teleport the Sole Survivor to the Institute and The Molecular Level will end, then starting a faction-specific quest and Institutionalized. The relay dish must also be connected to the same generator as the beam emitter for the teleporter to work.