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play linearity must remain within listed specifications of
Table 5-2 to the + and - 25 MHz positions.
g. Center the coarse IF CENTER FREQ control. Set the
DISPERSION control to 1 MHz position and apply 10 ns and
1 µs markers from the Time-Mark Generator.
h. Check-The range of the IF CENTER FREQ-FINE con-
trol. Must equal or and - 1 MHz.
i. Return the VERTICAL DISPLAY switch to LIN position.
Fig. 5-2. Measuring dispersion accuracy.
Fig. 5-3. Measuring dispersion linearity.
13. Check Resolution Bandwidth
a. Requirement-Resolution bandwidth is equal to or less
than 1 kHz, to 100 kHz or more.
b. Apply 200 MHz (5 ns) signal from the Time-Mark Gen-
erator to band B RF INPUT connector through 20 dB attenu-
ator. Tune CENTER FREQUENCY control to minimize inter-
ference of the converted signals (tunable signals).
c. Set the DISPERSION RANGE to kHz/DIV position and
the DISPERSION to 50 kHz/div. Uncouple the RESOLU-
TION and turn the control fully clockwise. Set the TIME/
DW to .1 s.
d. Adjust the GAIN control for an 8 division display
amplitude.
e. Check the bandwidth of the 200 MHz signal at the
-6 dB amplitude point by switching in -6 dB attenuation
with the IF ATTENUATOR switches and noting the -6 dB
amplitude point. Bandwidth must equal or exceed 100 kHz.
See Fig. 5-4A.
f. Change the RESOLUTION control to 1 kHz position
(fully counterclockwise) and the DISPERSION to 1 kHz/div
keeping the 200 MHz signal centered on screen with the
IF CENTER FREQ controls.
g. Check the resolution bandwidth at the -6 dB ampli-
tude point, Bandwidth must not exceed 1 kHz. See Fig. 5-4B.
h. Return the RESOLUTION to the coupled position and
set the DISPERSION-COUPLED RESOLUTION controls to
500 kHz/div position.
5-5
Summary of Contents for 491
Page 4: ...i i Fig 1 1 The Type 491 Spectrum Analyzer ...
Page 24: ...2 16 Fig 2 17 Control set up chart ...
Page 34: ...Fig 3 1 Function block diagram of the Type 491 3 2 ...
Page 42: ...Fig 3 10 Block diagram of the video detector and vertical amplifier 3 1 0 ...
Page 48: ......
Page 53: ...Fig 4 4 Power Supply Circuit board assembly with wiring color code 4 5 ...
Page 54: ...Fig 4 5 Horizontal Display circuit board assembly showing color code to pin connectors 4 6 ...
Page 55: ...Fig 4 6 IF Control board assembly Wiring color code to pin connector 4 7 ...
Page 64: ...Fig 4 20A Tube subassembly removal procedure 4 16 ...
Page 65: ...Fig 4 20B Tube subassembly installation procedure 4 17 ...
Page 68: ...Fig 4 22 Power supply board assembly with component call out 4 2 0 ...
Page 69: ...Fig 4 23 Vertical Amplifier and Blanking board assembly with component call out 4 21 ...
Page 70: ...Fig 4 24 IF control board assembly with component call out 4 22 ...
Page 71: ...Fig 4 24 IF control board assembly with component call out 4 23 ...
Page 72: ...Fig 4 25 Horizontal display board with component call out 4 24 ...
Page 73: ...Fig 4 25 Horizontal display board with component call out 4 25 ...
Page 74: ...Fig 4 26 Phase lock board with component call out 4 26 ...
Page 88: ......
Page 90: ...Fig 6 1 Test equipment recommended for calibration of the Type 491 6 2 ...
Page 138: ......
Page 192: ......
Page 195: ...SECTION II B 3 ...
Page 196: ......
Page 200: ......
Page 201: ...SECTION 9 DIAGRAMS MECHANICAL PARTS LIST ILLUSTRATIONS ACCESSORIES ...
Page 202: ......
Page 203: ...9 1 ...
Page 204: ...9 3 ...
Page 205: ...9 5 ...
Page 206: ...9 7 ...
Page 207: ...9 9 ...
Page 208: ...9 11 ...
Page 209: ...9 13 ...
Page 210: ...9 15 ...
Page 211: ...9 17 ...
Page 212: ...9 19 ...
Page 213: ...9 21 ...
Page 214: ...9 23 ...
Page 215: ...9 25 ...
Page 216: ...9 27 ...
Page 217: ...FIG 1 9 29 ...
Page 218: ...FIG 2 REAR 9 31 ...
Page 219: ...9 33 FIG 3 IF CHASSIS PHASE LOCK ASSEMBLIES ...
Page 220: ...FIG 4 POWER CHASSIS 9 35 ...
Page 221: ...FIG 5 TIME DIV SWITCH OSCILLATOR ASSEMBLIES 9 37 ...
Page 222: ...FIG 6 CRT SHIELD ASSEMBLY 9 39 ...
Page 223: ...FIG 7 CABINET ASSEMBLY HANDLE 9 4 1 ...
Page 224: ...FIG 8 491 STANDARD ACCESSORIES FIG 8 491 STANDARD ACCESSORIES 9 43 ...
Page 225: ......
Page 226: ...PIN 028017 000 ...