TABLE 5-2
F i g . 5 - 4 . D i s p l a y p a t t e r n w h e n r e s o l u t i o n i s c o r r e c t l y a d j u s t e d .
5 - 6
14. Check Dispersion Accuracy of kHz/div
Selections
Requirement: Dispersion accuracy. within 3% over + and
- 2.5 MHz range of the IF CENTER FREQUENCY.
a. Apply 10 ns and 1 µs markers from the Time-Mark
Generator through a 20 dB attenuator to band A, RF INPUT,
Set the band selector to A, and the DISPERSION to 500 kHz/
div.
N O T E
T h e m a r k e r s i g n a l s m a y a l s o b e a p l i e d t h r o u g h a
20 dB attenuator, a BNC to TNC adapter and the
W a v e q u i d e M i x e r A d a p t e r t o b a n d C R F I N P U T .
( T h i s b y p a s s e s t h e 1 s t m i x e r . )
b. Check-the range of the IF CENTER FREQ control by
rotating the control to the limit each side of center. Count
the number of 1 MHz (1 µs) markers from the IF feedthrough
signal. Must equal or exceed 2.5 MHz, Note the dial read-
ing when the control is 2.5 MHz from center. This reading
will be referred to later in the procedure.
c. Center the IF CENTER FREQ controls and change the
DISPERSION to 50 kHz/div. Apply 10 ns and 10 µs (100 kHz
markers) to the Type 491 RF INPUT.
d. Check-the range of the IF CENTER FREQ-FINE control.
Must equal or exceed 50 kHz either side of center.
e. Center the
IF CENTER FREQ
controls, change the DIS-
PERSION to 50 kHz/div and again apply 10 ns and 1 µs
markers to the RF INPUT.
f. Check-the dispersion accuracy at each DISPERSION
selector position listed in Table 5-3.
Measure dispersion within the center 8 div of the display
for each selector position and over the + and – 2.5 MHz
range of the IF center frequency. Check accuracy with the
IF CENTER FREQ control centered then rotate the control
t
O
the dial reading noted in step b at 2.5 MHz and recheck
dispersion accuracy.
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 ...