Tektronix 491 Manuel utilisateur

TM 9-6625-2467-15

DEPARTMENT OF THE ARMY TECHNICAL MANUAL

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT, GENERAL SUPPORT,

AND DEPOT MAINTENANCE MANUAL

(INCLUDING REPAIR PARTS)

SPECTRUM ANALYZER

(TEKTRONIX, INC. MODEL 491)

(6625-494-2937)

HEADQUARTERS,DEPARTMENT OF THE ARMY

DECEMBER 1969

WARNING

HIGH VOLTAGE

is used in the operation of this equipment.

DEATH ON CONTACT

may result if personnel fail to observe safety precautions.

Learn the areas containing high voltage

in each piece of equipment.

Be careful not to contact high-voltage or 115-volt ac input connections

when installing or operating this equipment.

Before working inside the equipment, turn power off and ground points of

high potential before touching them.

This manual

reproduced by

TECHNICAL MANUAL

)

No. 9-6625-2467-15 )

contains copyright material

permission of TEKTRONIX, Inc.

TM 9-6625-2467-15

HEADQUARTERS

DEPARTMENT OF THE ARMY

Washington, D.C., 15 December 1969

SPECTRUM ANALYZER (TEKTRONIX, INC. MODEL 491)

Section 1

Section 2

Section 3

Section 4

Section 5

Section 6

Section 7

Section 8

Section 9

APPENDIX A.

(6625-494-2937)

CONTENTS

Characteristics

Operating Instructions

Circuit Description

Maintenance

Performance Check

Calibration

Abbreviations and Symbols

Electrical Parts List

Mechanical Parts List Information

Mechanical Parts List

Diagrams

Mechanical Parts List Illustrations

Accessories

BASIC ISSUE ITEMS LIST

MAINTENANCE ALLOCATION CHART

REPAIR PARTS LIST

Abbreviations and symbols used in this manual

are based on or taken directly from IEEE Stand-

ard 260 “Standard Symbols for Units”, MIL-

STD-12B and other standards of the electronics

industry.

Fig. 1-1. The Type 491 Spectrum Analyzer.

SECTION 1

CHARACTERISTICS

The Type 491 Spectrum Analyzer is a wide band,

general purpose portable spectrum analyzer with an RF

center frequency range from 10 MHz to 40 GHz. The ana-

lyzer displays signal amplitude as a function of frequency

for a selected portion of the

played along the horizontal

amplitude on the vertical axis

spectrum, Frequency iS dis-

axis

of a (dispersion) and signal

self-contained system.

The following electrical characteristics apply at an ambient

temperature of 25° C (±5°C) after an initial warmup period

of approximately 20 minutes.

ELECTRICAL CHARACTERISTICS

Characteristic Performance Requirement Supplemental Information

RF Center

Frequency Range

10 MHz to 40 GHz—See Table 1-1

CW Sensitivity See Table 1-1

(S + N=2N)

Dial Accuracy

Within ± (2 MHz +1% of dial reading) IF CENTER FREQ central at 000, FINE IF

ICENTER FREQ control and FINE RF CENTER

FREQ controls centered.

TABLE 1-1

Minimum CW

Sensitivity (S + N = 2N)

Band and Supplemental

Scale RF CENTER FREQUENCY 1 kHz RESOLUTION 100 kHz RESOLUTION Information

A-1

10-275 MHz –100 dBm –80 dBm

B-2

275-900 MHz –110 dBm –90 dBm

800-2000 MHz –105 dBm –85 dBm

C-4

1.5-4.0 GHz –110 dBm –90 dBm

5 3.8-8.2 GHz –100 dBm -80 dBm

8.0-2.4 Ghz –95 dBm –75 dBm

712.4-18.0 GHz –90 dBm –70 dBm

18.0 -26,5 GHz

–80 dBm -60 dBm

26.5-40.0 GHz –70 dBm -50 dBm

Ω

source impedance.

All voltages are RMS.

TABLE 1-2

DISPERSION/DIV

Setting

Accuracy

Remarks

10MHz —

±3% (±0.3 MHz/Div) Over the ±25 MHz of the IF Center FREQ control ex-

5 MHz ±3% (±0.15 MHz/Div) cept the 10 MHz/DIV position (± 10 MHz). The DIS-

2 MHz PERSION CAL adjust can be reset to improve the ac-

±5% (±0.1 MHz/Div) curacy at a specific IF CENTER FREQ control setting

1 MHz ±7% (±70 kHz/Div) by using the front panel 1 MHz CAL MARKERS OUT as

.5 MHz ±10% (±50 kHz/Div) a calibrated signal.

.2 MHz ±15% (±30 kHz/Div) Measured over the center 8 divisions of the graticule.

1-1

ELECTRICAL CHARACTERISTICS (cont)

Characteristic Performance Requirement Supplemental Information

Dispersion

MHz/DIV RANGE

Range

.2 MHz/Div to 10 MHz/Div In a 1-2-5 seauence

Accuracy See Table 1-2

Linearity ±3% (over an 8 division display)

kHz/DIV RANGE

Range

1 kHz/Div to 500 kHz/Div in a 1-2-5 se-

quence and zero dispersion.

Accuracy ±3% of each setting Over the ±2.5 MHz range of the IF

CENTER FREQ control. Measured over the

center 8 divisions of the graticule.

Linearity ±3% (over an 8 divisions display)

Resolution ≤1 kHz to ≥100 kHz; in 11 uncalibrated May be coupled with the DISPERSION con-

steps. trol or switched separately.

IF Center Frequency

Control Range” IF CENTER FREQ FINE

1 kHz/DIV to 500 kHz/DIV

Dispersion ≥(+ and – 2.5 MHz) ≥(+ and – 50 kHz)

0.2 MHz/DIV to 5 MHz/DIV ≥(+ and – 25 MHz) ≥(+ and – 1 MHz)

10 MHz/DIV ≥(+ and – 10 MHz) ≥(+ and – 1 MHz)

IF Attenuation

Range 0 to 51 dB In combinations of 1, 2, 4, 8, 16 and 20 dB.

Accuracy ±0.1 dB/dB

IF GAIN Control

Range

≥50 dB

Display Flatness with IF CENTER 3 dB maximum amplitude variations from Band 1 (10 MHz to 275 MHz) 50 MHz dis-

FREQ at 000 10 MHz to 12.4 GHz. persion.

6 dB maximum amplitude variations from Bands 2 through 8 (275 MHz to 40 GHz]

12.4 GHz to 40 GHz 100 MHz dispersion.

Incidental FM

IF ≤200 Hz Typically 100 Hz. Up to 400 Hz if power

line frequency drops to 48 Hz.

IF + LO ≤300 Hz (at LO fundamental and with

phase lock operation)

Phase Lock

Internal Markers 1 MHz ±0.1% (Control next to OFF posi-

tion.)

INT REF FREQ Range At least 1 kHz but not more than 1.3 kHz

above measured frequency with the INT

REF FREQ control counterclockwise (next to

OFF position.)

Stability; Ref. Osc. ≤1 port in 107.

(Short term FM)

External Phase Lock

Reference Input

Frequency 1 MHz to 5 MHz

Voltage 1 to 5 volts peak to peak.

Display Functions

Dynamic Range

LOG

LIN

SQ LAW

Maximum Input Power

≥40 dB with 8 division display

≥26 dB with 8 division display

Instrument must be inside the dust cover.

≥13 db with 8 division display

-30 dBm for linear operation See Fig. 2-8

+15 dBm diode mixer, power limit

1-2

Characteristic

Tube Type

Phosphor

Accelerating Potential

Graticule Type

Area

Illumination

Unblinking

TIME BASE

Characteristic Performance Requirement Supplemental Information

RECORDER Output ≥4 mV per displayed division amplitude of Rear panel connector

signal in LIN made.

Sweep Range 10 µs/div to 0.5 s/div In a 1, 2, 5 sequence

Sweep Accuracy ±3%Measured within the center 8 divisions

VARIABLE Time/Div ≥2.5:1 An uncalibrated control provides continu-

ously variable sweep rates from 10 µs/div

to approximately 1.25 s/div.

Sweep Length 10.5 divisions ±0.2 div.

Sawtooth Output 70 mV to 90 mV (P-P) Rear panel connector

TRIGGERING

Trigger Sensitivity

Internal ≤0.2 division, 20 Hz to 100 kHz

External ≤0.2 volt, 20 Hz to 100 kHz

Maximum Input Voltage 100 volts (DC + peak AC)

POWER REQUIREMENTS

Input Voltage

115-volt range LOW- 90 to 110 VAC

MED- 104 to 126 VAC

HIGH- 112 to 136 VACLine voltage ranges provide regulated DC

230-volt range LOW- 180 to 220 VAC voltages, when line contains less than 2%

MED- 208 to 252 VAC total harmonic distortion.

HIGH- 224 to 272 VAC

Line Frequency 48 to 440 Hz

Input Power 55 watts maximum

CATHODE RAY TUBE

Information

T4910-7-1

Approximately 3.75 kV

internal

8 divisions vertical by 10 divisions horizontal

Construction

Finish

Overall Dimensions [measured

at maximum points]

Each division equals 0.8 cm.

Variable edge lighting

Deflection type, DC coupled

MECHANICAL CHARACTERISTICS

Alluminum-alloy chassis, panel and cabinet

Glass laminate etched-circuit boards

Anodized panel, blue vinyl-coated cabinet

7¼” high, 12½" wide, 23½” long (includes

ENVIRONMENTAL

The following environmental test limits apply when tested

in accordance with the recommended test procedure. This

instrument will meet the electrical performance requirements

given in this section, following an environmental test.

panel cover and carrying handle)

CHARACTERISTICS

1-3

Characteristic

Temperature

Operating

Non-operating

Altitude

Operating

Non-operating

Humidity

Non-operating

Electromagnetic Interference (EMI)

Radiated Interference

Conducted Interference

Vibration

Operating

Shock

Operating and non-operating

Transportation

Package vibration

Package drop

Performance Requirement

–15° C to +55° C

–55° C to +75° C

15,000 feet maximum

Five cycles (120 hours) of

Method 106B

150 kHz to 1000 MHz

150 kHz to 25 MHz

Mil-Std-202C,

Resonant searches along all 3 axes at 0.025

inches, frequency varied fram 10-55 c/s. All

major resonances must be above 55 c/s.

One shock of 30 G, one-half sine, 11 milli-

second duration each direction along each

major axis.

Meets National Safe Transient type of test

when correctly packaged. One hour vibra-

tion slightly in excess of 1 G.

30 inch (18-inches for R491) drop on any

corner, edge or flat surface.

Supplemental Information

Automatic resetting thermal cutout protects

instrument from overheating.

Altitude referred to sea level. Operating

temperature capabilities decline 10 C per

1000 feet altitude above sea level.

May be tested during non-operating tem-

perature test.

Exclude freezing and vibration.

Tested within an electrically shielded enclo-

sure with the CRT mesh filter installed.

Within the limits described in MIL-I-6181D,

Figs. 7, 8, 14 and 16.

Conducted interference through the power

cord.

Instrument secured to vibration platform

during test. Total vibration time, about 55

minutes.

Guillotine-type shocks. Total of 12 shocks.

Package should just leave vibration surface

1-4

SECTION 2

OPERATING INSTRUCTIONS

Introduction

A Spectrum Analyzer is an instrument that graphically

presents a plot of signal amplitude as a function of frequency

for a selected portion of the spectrum. The Type 491 is

designed to provide a spectral display of the frequency

distribution of electromagnetic energy within the frequency

range of 10 MHz to 40 GHz. Signals are displayed as a

spectrum on a CRT screen with signal energy plotted on the

vertical axis against frequency on the horizontal axis.

The Type 491 can be operated from either 115 or 230-volt

nominal line voltage with a range from 90 to 136 VAC or

180 to 272 VAC. Two selector-type connectors on the power

input panel may be positioned to accommodate these volt-

age ranges. The selection assembly also includes two line

fuses which are positioned correctly when the correct selec-

tion is made for either 115 or 230-volt nominal operation.

Fig. 2-3 shows the power input panel on the rear of the

instrument and the voltage range and nominal line voltage

selectors.

This type of display provides the following information;

The presence or absence of signals, their frequencies, fre-

quency drift, relative amplitude of the signals and the nature

of modulation if any, plus many other characteristics.

This section of the manual describes the function of the

front and rear panel controls and connectors, power supply

connection, and a procedure for first time operation, to intro-

duce the operator to the operational functions of the controls.

The remainder af the section then describes operation tech-

nique with some measurement applications and signal

interpretations.

Front Cover and Handle

The front cover furnished with the Type 491 provides a

dust tight seal around the front panel. Use the cover to

protect the front panel when storing or transporting the

instrument, The cover also provides storage for the external

waveguide mixers and other accessories. See Fig. 2-1.

CAUTION

Removing or replacing the dust cover on the instru-

ment may be hazardous, if the” instrument is lifted

out of, or slid into, the dust cover. To remove or

replace the dust cover, set the instrument on a

bench or table, then slide the cover off or on the

instrument. The instrument may also be set on the

front panel cover and the dust cover slipped on or

off the instrument. Do not set the instrument on

the front panel controls.

The handle of the Type 491 can be positioned to carry

the instrument or it can be positioned at several angles to

serve as a tilt-stand. To position the handle, press in at both

pivot points (see Fig. 2-2) and adjust the handle to the

desired position. The instrument may also be set upright

on the rear panel feet for operation or storage.

Voltage Considerations

Fig. 2-1. Accessory storage provided in the front cover of the Type

491

2-1

Fig. 2-2. Handle positioned to provide a stand for the instrument.

CAUTION

The Type 491 should not be operated with these

voltage selector switches in improper positions.

Operation of the instrument with incorrect voltages

will either blow the protective fuses or the instru-

ment will not operate properly.

The Voltage Range Selector located on the rear panel

permits the instrument to operate on line voltages above and

below the nominal 115 or 230 volts. Each selection provides

correct regulation through an overlap voltage range into the

next higher or lower range. It is best to select a range with

its center voltage near your nominal line voltage, thus pro-

viding adequate regulation over a plus and minus devia-

tion of the input line voltage.

The following procedure will prepare the instrument for

operation at your average input line voltage:

1. Remove the cover assembly over the selectors by

unscrewing the two cap screws, then pull the cover with the

attached fuses away from the panel.

2. Pull the Line Voltage Selector out and turn the connector

around to plug it back into the correct position.

3. To change the regulating range, pull out the Range

Selector bar, slide it to the desired range and plug it into

the correct position. Select a range which is centered about

the average line voltage to be applied to the instrument.

See Fig. 2-3.

4. Re-install the cover. Make certain the cover fits firmly

against the rear panel, so the line fuses are seated in their

sockets, and tighten the two cap screws.

5. Before applying power to the instrument, check that the

indicating tabs on the switch bars are protruding through

the correct holes for the desired voltage setup.

2-2

Fig. 2-3. Power panel and selectors.

Spectrum Analyzer Terms

The following glossary of spectrum analyzer terms is pre-

sented as an aid to understanding the terms as they are used

in this manual.

Spectrum Analyzer-A device that displays a graph of the

relative power distribution as a function of frequency, typi-

cally on a cathode-ray tube or chart recorder.

Types: Real-time and non real-time.

A real-time spectrum analyzer performs a continuous

analysis of the incoming signal, with the time sequence of

events preserved between input and output.

A non-real-time spectrum analyzer performs an analysis

of repetitive events by a sampling process.

Methods: Swept front end and swept intermediate fre-

quency.

A swept front end spectrum analyzer is a superheterodyne

spectrum analyzer in which the first local oscillator is swept.

A swept IF spectrum analyzer is a superheterodyne spec-

trum analyzer in which a local oscillator other than the first

is swept.

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