Ampex figured out the secret to recording video on magnetic tape was to use a rotating head, which increases information density on the tape by creating magnetic fields across the width of the tape and not just linearly. The rotating head approach was used throughout the life of the video tape recording era.
Even with this invention, info density wasn’t great for the Ampex. The two-inch-wide tape had to move at 14 inches/sec, which meant a 60 minute reel had (does math) 4200 feet of tape!
