Question:

I am just wondering if we can join alive prayers when they are broadcast.

Answer:

The scholars say this is not allowed, since one’s prayer line must be
connected or in view of the rest of those praying. Listening on a
loud speaker is okay if there is a physical connection (like a hallway
or stairwell or balcony) that is connected to the others praying. But
on a broadcast there is no physical connection. Some of the Madhahab
even limit the distance between the prayer lines.

Allah knows best.