When MacGyver bends the antenna to slide down the cable on, he bends it in the shape of a candy cane with a large bend where it sits on the cable. However, when MacGyver puts it on the cable, the bend is almost at a 90-degree angle, much less of a bend then there was just a moment before.
Because of the steepness of the angle of the cable from the top of the building to the ground, MacGyver and Mei Jan should have been traveling at a very high rate of speed when they reached the ground. Assuming they would have survived the landing, they should have been severely injured.