How to unlock: The quest unlocks automatically after completing the Hunter/Hunted main quest in the Greenetech Genetics (M5,4) location.
- Give the courser chip for analysis
- Find the Railroad - this objective will activate only if you haven't contacted with that faction before
- Go back to Virgil
- Organize help for building the signal interceptor
- (Optional) Talk with the Minutemen - you can ask only one faction for help
- (Optional) Talk with the Railroad - you can ask only one faction for help
- (Optional) Talk with the Brotherhood of Steel - you can ask only one faction for help
- See what the faction's scientist has to say - each faction has different specialist with whom you must talk
- Build the Reflector Platform
- Build the console
- Build the relay dish
- Build the beam emitter
- (Optional) Find the bio scanner in the hospitals - the objective will become active only if you have no bio scanners in your inventory
- (Optional) Find the sensor module near the telecommunication infrastructure - the objective will become active only if you have no sensor module in your inventory
- (Optional) Find the proper circuit board in the military facilities - the objective will become active only if you have no circuit boards in your inventory
- Provide power for the signal interceptor
- Use the signal interceptor
Important! It is recommended to perform a manual save of the game after you finish the conversation with Virgil at the start of this quest. Further quest objectives are related to creating stronger bonds with one of three main factions. It will not make other factions unfriendly towards you, but it is better to secure yourself anyway, especially if you're not one hundred percent sure which faction you plan to help later in the game.
Giving the courser chip for analysis
Return to doctor Amari with the chip obtained in the previous main quest. She can be found in the Memory Den building in Goodneighbor. Once you reach the office in the basement of the building, start the conversation with Amari and show her the chip. The woman will send you to search the Railroad faction which will be able to crack the protection of the chip.
Finding the Railroad
If up to now you haven't found the Railroad faction, now you must do it by completing the Road to Freedom quest. Completion of the quest is needed even if you don't plan to cooperate with the group later in the game. If you have found the headquarters of the faction, then you can skip this part and go directly to the end of this section - the meeting with Desdemona in Railroad H.Q.
The Road to Freedom quest mentioned earlier can be unlocked in few ways. The easiest one is overhearing the conversation of two men in the Diamond City Market. They can be found north from the main trading plaza, near Nick Valentine's detective agency.
You can also go straight to the park in the center of the city that is marked as the mission objective's destination. There you will find a marker on the ground from which a red line is leading somewhere. It is quite long and not always visible, so you must be cautious. You can ignore the enemies you met: ghouls, thugs and mutants. Simply follow the path.
The road ends before the white door which leads to the Old North Church. Inside turn immediately right in order to avoid the ghouls and walk through the door to the basement.
There, at the last wall you will notice a symbol on the wall. It is a lock which outside's face (the one with letters) can be turned and selected by pressing the middle button. You must create a "RAILROAD" password from the letters on the face and confirm each word by pressing the button. Once you do it, the secret passage will open. Now you can walk into the next room where you will meet Desdemona.
If this is your first encounter with Desdemona, first you must answer few of her questions. If you have made contact with the faction earlier, you can walk directly to Railroad H.Q. and talk to her. No matter the circumstances of the meeting, you must mention doctor Amari and the courser chip that you have. The next person with which you must talk is Tinker Tom who can be also found in the H.Q. Agree to give the chip to the Railroad (if needed, you will be able to reclaim it later in the game) and wait for Tom to finish analyzing the item. He will give you the Courser Chip Data holotape.
Return to Virgil
Leave Railroad faction's headquarters and go again to the Rocky Cave located in the southwestern corner of the map. Enter the cave, talk to Virgil and give him the data you obtained. He will inform you that you must build a signal interceptor and he will give you the plans of the device. You will need to ask one of the factions for help in constructing the device. This topic is described on the next page of the walkthrough.