After the satellite dish is replaced, the Galaxy News Radio signal increases in quality and can be heard throughout the Capital Wasteland. Tune into GNR and, shortly after the dish is fixed, Three Dog will talk about the improved signal.
If you don't make the speech check or fail it, you can't get into the weapons cache in Hamilton's Hideaway. Three Dog does not possess the key either, so killing him will not work.
Behind the scenes
After the relay has been repaired, Three Dog makes a one-off broadcast which includes the phrase "you can't stop the signal". This is a tagline of Mr. Universe from the 2005 sci-fi movie Serenity. Mr. Universe broadcasts the truth, whether pleasant or not. This is similar to Three Dog's fighting the "good fight".
PCPlayStation 3Xbox 360 Sometimes, after you mount the dish, the front door to the Galaxy News Radio Station will be locked, and will need a "key". There is no way to get the key for the door, and, if you talk to the intercom, it will only repeat "Door's open. Quit buzzin me, willya?" This happens if you exit out the front door instead of the back door when Three Dog tells you to, or if you exit out the back door before you talk to Three Dog.
PCPlayStation 3 If you successfully pass the Speech check which allows you to circumvent the quest as a requirement for getting information on James, whenever you talk to Three Dog in the future, he will always respond with "Ready to make a deal?" and is under the misapprehension that you still "need" information on Dad. Even if the player successfully completes all quests related to James and his story is completed, Three Dog will still only talk about taking on his "deal" and that without it, there will be "no dad" .