How long has Ben been locking the signals? Was the video of Juilet's sister real? Did he just use the implosion of the Swan as an excuse to cut off communications?

How long has Ben been locking the signals? Was the video of Juilet's sister real? Did he just use the implosion of the Swan as an excuse to cut off communications?And why did Dharma need an underwater signal jamming station? The Others don't strike me as the type to build that kind of technology themselves.

And why did Dharma need an underwater signal jamming station?

To jam the signals!

Underwater - Maybe to not let other Dharmaites know the signals were being blocked.

Signal Jamming - To not let the outside world know about the island. The island is apparently mystical & the dharma research was not exactly explanable in easy terms.

How long has Ben been locking the signals? Was the video of Juilet's sister real? Did he just use the implosion of the Swan as an excuse to cut off communications?

I think Ben has been controlling things (including blocking communications) for as long as he has been able to, maybe for years. And that he un-blocked the signal to pull in the video of the Flight 815 news coverage and the video of Juliet's sister.

ZotBot

How long has Ben been locking the signals? Was the video of Juilet's sister real? Did he just use the implosion of the Swan as an excuse to cut off communications?
Juliet said they were blocking all signals except for their own. Ben and the others could still communicate until (maybe) the sky turned purple.