1、SUPTE RPJZL 94 m 8357401 0001520 Bb2 - RP 11-1994 Revision of RP 1 1-1 984 SMPTE RECOMMENDED PRACTICE Tape Vacuum Guide Configuration and Position for Quadruplex Video Magnetic Tape Recording 1 Scope This practice specifies the tape vacuum guide config- uration and position for quadruplex video reco
2、rdings on 2-in magnetic tape, and the test conditions for verifying these parameters. 2 Mechanical dimensions 2.1 The radius of the tape vacuum guide (dimen- sion Ri) shall be 1 .O334 in + 0.0000 in - 0.0004 in (26.248 mm + 0.000 mm - 0.010 mm). 2.2 The radius of the entrance contour (dimen- sion R2
3、) shall be 0.156 in t 0.000 in - 0.005 in (3.96 mm + 0.00 mm - 0.13 mm). 2.3 The arc of the vacuum guide (dimension A) shall be 1.940 in 2 0.005 in (49.28 mm -c 0.13 mm). 3 Guide position for recordings The center of curvature of the vacuum guide shall lie between the axis of rotation of the video p
4、ole tips and the vacuum guide (see figure 1). The extension of a line joining the center of curvature of the vacuum guide and the axis of rotation of the heads shall intersect the tape at the midpoint of its width. The distance (eccentricity) between the center of curva- ture of the vacuum guide and
5、 the axis of rotation of the heads shall be zero when the radius Ri has its maximum permitted value (see2.1) and shall increase by the same amount by which the radius Ri de- creases from its maximum permitted value. Table l shows an example of such dimensional dependence. The dimensions are based on
6、 a nominal tape thick- ness of 0.001 4 in (0.036 mm) and a radius of rotation of the magnetic head pole tips of 1 .O329 in minimum to 1.0352 in maximum (26.236 mm minimum to 26.294 mm maximum). Page 1 of 2 pages Figure 1 -Tape vacuum guide configuration Table 1 - Specifications Vacuum guide radius E
7、ccentricity 1 Inches Millimeters Inches Millimeters 1.0334 26.248 0.0000 0.000 1.0333 26.246 0.0001 0.003 1.0332 26.243 0.0002 0.005 1.0331 26.241 0.0003 0.008 1.0330 26.238 0.0004 0.010 Copyright O 1994 by the SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., White Plains, N
8、Y 10607 (914) 761-1100 Approved February 28, 1994 SMPTE RP*LL 94 8357YOL OOOL52L T9 RP 11-1994 4 Test conditions Temperature for other tests: 23C I 1C (73F 2 2F) Tests and measurements made on the recorder to check the requirements of this practice shall be made under the following atmospheric condi
9、tions: Relative humidity: (50 I 2)% Barometric pressure: 86 kPa to 106 kPa (860 mbar to 1060 mbar) Temperature for drum diameter: 23C f 0.5“C (73F I 1 “F) Conditioning before testing: 24 h Annex A (informative) Interchangeability Achievement of tape reproducing interchangeability requires, among oth
10、er things, that means be provided to accommodate variations of (a) the radius of rotation of the magnetic head pole tips, (b) the radius of the vacuum guide, and (c) tape thickness. These effects are compensated by the stretching of the tape into a slot cavity in the vacuum guide by virtue of the ra
11、dius of rotation of the magnetic head pole tips projecting beyond the unstretched oxide surface of the tape as held in the vacuum guide. Over the limits normally encountered, the stretching provides automatic compensation if the vacuum guide is positioned to give the minimum geometric distortion in the reproduced picture. Page 2 of 2 pages
