The first Crimson Radio really is on a tower.
You have to climb up and jump on the beams to get up to the platform.
Remember to keep holding down the jump button so your alter ego can pull him/herself up.
Here are some screenshots...
The second tower is at a logging camp.
The camp is locked and is opened at a certain step of the Story Missions.
So if you can't get there yet, continue with the story until you can...