37.
a.
b.
Fig. 6-41. Typical equipment setup to check response flatness, sensitivity, frequency calibration and phase lock operation.
Adjust Band A Mixer Balance—Check
Amplitude of Spurious Signals from Internal
Sources
Equipment setup is shown in Fig. 6-40.
Connect a 50
Ω
termination to band A RF INPUT con-
nector. Switch the band selector to A.
c. Adjust the GAIN control so noise amplitude is about
1 division.
d. Tune the RF CENTER FREQUENCY to the low end of
the dial against the stop. At this center frequency setting
with a dispersion of 2 MHz/div, a local oscillator feedthrough
spur should be visible on the display.
e. Tune the RF CENTER FREQUENCY to center the feed-
through spur, then decrease the dispersion to 1 MHz/div.
f. Adjust C14, C16 and R13 (band A mixer, see Fig. 6-39)
to minimize the amplitude of this feedthrough spur over the
5 MHz dispersion window.
g. Check through band A frequency range for spurious
signals. Amplitude of any spur with the exception of the local
oscillator feedthrough signal must not exceed
2×
n o i s e
amplitude. If a spur appears at approximately 37.5 MHz,
readjust the mixer balance.
h. Move the 50
Ω
termination to band B RF INPUT con-
nector, switch the band selector to B and set the DISPER-
SION to 10 MHz/div.
i. Adjust the GAIN control for 1 division of noise, then
tune through the band B frequency range checking for spuri-
ous signals whose amplitude exceeds
2×
noise level.
j. Move the 50
Ω
termination to band C RF INPUT con-
nector. Set the band selector to C.
k. Check through the frequency range of band C for
spurious signals with amplitudes that should exceed
2 ×
noise level.
38A. Check Dial Accuracy, Analyzer Sensitivity
and Local Oscillator Phase Lock Operation
N O T E
Since signal generators with calibrated attenuators
a r e r e q u i r e d t o c h e c k s e n s i t i v i t y , d i a l a c c u r a c y
can be checked by the same instruments, provided
t h e s i g n a l s o u r c e h a s a n a c c u r a c y w i t h i n 0 . 1 %
a t t h e d i a l c h e c k p o i n t s . T h e s i g n a l g e n e r a t a r s
listed in Table 6-9 may be used if their accuracy is
checked near each dial check point, by a frequency
counter or by the beat frequency indicator against
some accurate reference frequency.
6-40
Содержание 491
Страница 4: ...i i Fig 1 1 The Type 491 Spectrum Analyzer ...
Страница 24: ...2 16 Fig 2 17 Control set up chart ...
Страница 34: ...Fig 3 1 Function block diagram of the Type 491 3 2 ...
Страница 42: ...Fig 3 10 Block diagram of the video detector and vertical amplifier 3 1 0 ...
Страница 48: ......
Страница 53: ...Fig 4 4 Power Supply Circuit board assembly with wiring color code 4 5 ...
Страница 54: ...Fig 4 5 Horizontal Display circuit board assembly showing color code to pin connectors 4 6 ...
Страница 55: ...Fig 4 6 IF Control board assembly Wiring color code to pin connector 4 7 ...
Страница 64: ...Fig 4 20A Tube subassembly removal procedure 4 16 ...
Страница 65: ...Fig 4 20B Tube subassembly installation procedure 4 17 ...
Страница 68: ...Fig 4 22 Power supply board assembly with component call out 4 2 0 ...
Страница 69: ...Fig 4 23 Vertical Amplifier and Blanking board assembly with component call out 4 21 ...
Страница 70: ...Fig 4 24 IF control board assembly with component call out 4 22 ...
Страница 71: ...Fig 4 24 IF control board assembly with component call out 4 23 ...
Страница 72: ...Fig 4 25 Horizontal display board with component call out 4 24 ...
Страница 73: ...Fig 4 25 Horizontal display board with component call out 4 25 ...
Страница 74: ...Fig 4 26 Phase lock board with component call out 4 26 ...
Страница 88: ......
Страница 90: ...Fig 6 1 Test equipment recommended for calibration of the Type 491 6 2 ...
Страница 91: ...Fig 6 2 Test equipment recommended to measure the dial accuracy receiver sensitivity and response flatness 6 3 ...
Страница 138: ......
Страница 191: ...APPENDIX A BASIC ISSUE ITEMS LIST Basic issue items list will be published at a later date A 1 ...
Страница 192: ......
Страница 195: ...SECTION II B 3 ...
Страница 196: ......
Страница 200: ......
Страница 201: ...SECTION 9 DIAGRAMS MECHANICAL PARTS LIST ILLUSTRATIONS ACCESSORIES ...
Страница 202: ......
Страница 203: ...9 1 ...
Страница 204: ...9 3 ...
Страница 205: ...9 5 ...
Страница 206: ...9 7 ...
Страница 207: ...9 9 ...
Страница 208: ...9 11 ...
Страница 209: ...9 13 ...
Страница 210: ...9 15 ...
Страница 211: ...9 17 ...
Страница 212: ...9 19 ...
Страница 213: ...9 21 ...
Страница 214: ...9 23 ...
Страница 215: ...9 25 ...
Страница 216: ...9 27 ...
Страница 217: ...FIG 1 9 29 ...
Страница 218: ...FIG 2 REAR 9 31 ...
Страница 219: ...9 33 FIG 3 IF CHASSIS PHASE LOCK ASSEMBLIES ...
Страница 220: ...FIG 4 POWER CHASSIS 9 35 ...
Страница 221: ...FIG 5 TIME DIV SWITCH OSCILLATOR ASSEMBLIES 9 37 ...
Страница 222: ...FIG 6 CRT SHIELD ASSEMBLY 9 39 ...
Страница 223: ...FIG 7 CABINET ASSEMBLY HANDLE 9 4 1 ...
Страница 224: ...FIG 8 491 STANDARD ACCESSORIES FIG 8 491 STANDARD ACCESSORIES 9 43 ...
Страница 225: ......
Страница 226: ...PIN 028017 000 ...