Fig. 2-22. Pulse shaping effects on the pulse spectrum.
2-20
Fig. 2-23. Frequency difference measurement between two signals.
cillator fundamental. If an incorrect dial scale is used to
measure the frequency movement of the signal, as the RF
CENTER FREQUENCY is tuned, an erroneous reading will
be obtained, This erroneous reading however can be used
to identify which scale to use to obtain the corect frequency
r e a d i n g . F o r e x a m p l e : W i t h a d i s p e r s i o n o f 5 M H z / d i v
(50 MHz total) a given signal moves 50 MHz for a RF CEN-
T E R F R E Q U E N C Y c h a n g e o f 2 5 M H z . T h i s i n d i c a t e s t h e
signal is mixing with the next higher harmonic of the os-
cillator, and the next higher scale should be used to read
the signal frequency. If the signal only moves 25 MHz for
an RF CENTER FREQUENCY change of 50 MHz, the next
lower scale should be used.
6. The rate at which the signal moves across the disper-
sion window as the RF CENTER FREQUENCY is tuned also
aids in identifying which scale to use, and with practice,
the correlation of the signal rate of movement and the dial
scale becomes fairly easy.
Spurious responses due to intermodulation are the most
difficult to identify. Signal characteristics, such as type and
amount of modulation, irregular spacing between signals,
etc., are the main character identities.
APPLICATIONS
The spectrum analyzer is a very versatile device in the field
of radiation measurements. It can be used for example, as
an aid in the design and adjustment of transmitters, to check
and calibrate oscillators, check and calibrate attenuators, or
as a sensitive detector device to study all types of modu-
lated signals, plus many more special applications.
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 ...
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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 ...