Magnetic Tape Storage and Handling
A Guide for Libraries and Archives
Dr. John W.C. Van Bogart
Go back to: 1. Introduction
Figure 1. Diagram of a Tape Reel A schematic of a tape reel showing the principal components. Tape is wound around the hub of a tape reel forming a tape pack. The tape pack is protected from damage and disruption by flanges on the reel.
Figure 2. Cross Section of Magnetic Tape Magnetic particles are held together with a binder coated on a film substrate. Lubricant and other agents (not shown) may also be included in the top coat layer. A back coat may also be added to control friction and static charges. The structure of the top coat is analogous to that of Jell-O filled with grapes where the grapes represented the magnetic particles and the Jell-O represented thebinder.
2.1 Binder Degradation
2.2 Magnetic Particle Instabilities
2.3 Substrate Deformation
2.4 Format Issues
Helical versus Longitudinal Scan Recording
Figure 3. Helical Scan Recording A moving tape wraps 180° around a cylindrical drum rotating at high speeds; the rotating head is oriented at a slight angle to the tape so that the tracks written by the tiny record head embedded in the surface of the rotating drum run diagonally across the tape from one side to the other.
Figure 4. Types of Mistracking for Helical Scan Recording Trapezoidal error occurs when the angle of the recorded track does not agree with the scan angle of the playback head. Curvature error occurs when the tape has deformed nonlinearly. The playback signal corresponds to that for a single helical scan.
Figure 5. Longitudinal Recording A moving tape passes across a stationary record head. The recorded tracks are parallel to the edge of the tape and run the full length of the tape. A nine-track tape is shown.