Portals or stargates are frequency locked pockets through the ether, its debatable whether its called faster than light travel or not because its not actually traveling, its more like teleportation than travel.if you can travel vast distances through a wormhole then everything in it goes vast distances so id say if you shoot a radio signal into it then like everything in the worm hole it to may go the same way so thats like faster than light radio transmission isnt it using the same wormhole to take it to the other side of the galaxy like on stargate they communicate through the open worm hole on earth to the other side of the galaxy in instantly and the very ideas for that even on a movie has to come from somewhere or is it downloaded into the stargate creators own mind and may be based on factual reality after all
Pedantics aside, yeah you could maybe communicate that way but radio is awful primitive. It will be long left behind before we can traverse portals openly.
The problem is radio waves are sensitive to other em fields. And suns and black holes are awful full of em activity.