During the course of The Missing Link, you’ll meet Rose for the first time. To continue following Madigan’s trail, you need to convince Rose to let you up to the third floor of Top of the World, and to do that you need to complete the Fallout 76 Signal Strength main quest.
How to Complete the Fallout 76 Signal Strength Main Quest
Unlike previous main quests, the Fallout 76 Signal Strength quest doesn’t start automatically when you complete the previous main quest. With The Missing Link on hold, you need to first listen to the Top of the World radio station; this station will appear on your Pip-Boy whenever you’re close to Top of the World. Doing so will start the Signal Strength quest. Your first objective is to retrieve the Signal Repeater Schematic from Seneca Rocks Visitor Centre. This site can be found southwest of Top of the World. When you arrive, search the second floor for the body of Major Darion Jones; he has both the Signal Repeater Schematics and Signal Repeater Notes in his inventory.
Read the notes, which will tell you what ingredients you’ll need to make the Repeater. One of these can be found south of Greg’s Mine Supply. This location should already be familiar to you, as you got a fuse there during the An Ounce of Prevention main quest. Fast travel back there and make your way south; The SMU-97 Transponder can be found at Horizon’s Rest, where you’ll come across the wreckage of a crashed plane. It’s located in the cockpit of the plane.
The second part is nearer to Top of the World. The easiest way to reach it is to start at Top of the World and follow the train tracks southward. This will lead you to 98 NAR Regional. Search the train cars on the north side of the area to find the RCX01-A39 Duplexer. Once you have both parts, use any Tinker’s Workbench to craft Rose’s Signal Repeater.
Installing the Signal Repeater for Rose
Now that you have the Signal Repeater, you need to install it. This task requires you to travel to the National Isolated Radio Array. This small site is located southeast from Top of the World. There, install the Repeater and then search a nearby station for a terminal. This can be found to the southwest of the spot where you installed the Repeater. Using the terminal, choose the “Auxiliary Component Control,” option, then “Divert Power to Auxiliary Component.”
With the Repeater up and running, return to Top of the World. Rose will now let you up to the third floor, where the quest will complete. You’ll receive a random aid item, a random plan, random ammo, a new photo frame, and there’s a chance that you’ll also receive a Death Tambo or Guitar Sword.