Wavetek 132 User Manual

MODEL 132

VCG/NOISE

GENERATOR

@ -

1981 - Wavetek

THIS DOCUMENT CONTAINS INFORMATION PROPRIETARY TO
WAVETEK AND IS SOLELY FOR INSTRUMENT OPERATION AND
MAINTENANCE. THE INFORMATION IN THIS DOCUMENT MAY

NOT BE DUPLICATED IN ANY MANNER WITHOUT THE PRIOR

APPROVAL IN WRITING OF WAVETEK.

SAN DIEGO

9045 Balboa Ave., San Diego, CA 92123

P. 0 Box 651,

Tel [phone] TWX 91 O-335-2007

San

Diego, Calif. 92112

Manual Revision: 10181

Instrument Release: U-l 0180

CONTENTS

Section One

Section Two

Section Three CIRCUIT DESCRIPTION

Section Four

Section Five DATA PACKAGE

SPECIFICATIONS

Physical and Electrical Specifications

OPERATION

Inspection
Operating Controls
Operation

General Description

MAINTENANCE

Introduction

Recommended Test Equipment
Checkout and Calibration
Troubleshooting

Introduction

Recommended Spare Parts List

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1

3
4
7

11

13
13
13
16

21

21

SCOPE OF MANUAL

This manual contains instructions for operating, test- The Model 132 is a source of analog and digital

ing, and maintaining the Wavetek Model 132
Noise Generator. The Wavetek product-improvement waveforms. Noise outputs, or waveforms can
program ensures that the latest electronic developments
are incorporated into the Wavetek instruments by the brated signal-to-noise and noise-to-signal ratios to
addition of circuit and component changes as rapidly
as development and testing permit. Due to the time re­quired to document and print this manual, it is not
always possible to incorporate these changes into the
manual. In this case, data will be found on engineering
change sheets at the back of the manual. If there are no
change sheets, the manual is correct as printed.

VCG/

SCOPE OF EQUIPMENT

as well as a precision source of sine, triangle and

individually, or combined to provide selectable, cali-

+60

dB. Waveforms can be varied over a frequency
range of 0.2 Hz to 2 MHz. Length of the digital se­quence is selectable to a maximum of
Clock rates, variable from 160 Hz through 1.6 MHz,
give added versatility to the noise generator. These
clock rates allow selectable noise bandwidths variable
from 10 Hz to 100 kHz.

noise,

square

be used

220 - 1 bits.

SAFETY

Thi s

instrument i s

ss earth grou n

bYPa

BEFORE PLUGGING IN the instrument, comply with installation instructions.

wire dfor earth g r ounding via the
ding w

ith two wir eextension cords,

facil i ty powe r

adapter setc.

plug

wiring.

Do not

MAINT

ENANCE

shoul d

be don e

WARNING
operations.

CAUTION notes call attention to possible equipment damage in subsequent operations.

may requir epower on w i th th e

only by qualif

notes call attention t o

ied

personne l aware

possible injury or death hazards i n

instrumen t

of the elect

cover s

rica l

h a

removed.

zards.

subsequent

SECTIO N

1

SPECIFICATIONS

VERSATILITY

Waveforms
Sine
and analog noise

Frequency Range of Signal

0.2 Hz to 2 MHz in 6 decade ranges

Ranges
x10
Xl00
X1K
X10K
XIOOK
X1M

Function Outputs
Sine
with 60 dB step attenuator in 10

lapping calibrated vernier;

20 V p-p into open circuit and 10 V p-p into

load from

Sync Output

Greater than 1 V p-p square wave into open circuit at

6OOa

DC Offset

*5

V offset

from rear panel; peak amplitude limited by the dynam-

ic range of the amplifier output.

VCG

Frequency of the generator may be dc-programmed,
or ac-modulated by external 0 to
control circuitry is capable of 1000: 1 deviation. The

VCG amplifier has a 100 kHz bandwidth and a slew

rate of 0.1

result of the sum of the dial setting and the externally
applied voltage.

Stability
Short term

Long term
Percentages apply to amplitude, frequency, and dc
offset.

square

YJ

,

M.r

\

,

square f-l~

5Oa

source impedance.

output impedance.

(22.5

V offset into

-

Voltage Controlled Generator

V&s.

The instantaneous frequency is the

triangle

I-I

,

or

digital noise

,

,

and triangle

5Oa

dB

output impedance,

5Ofi

*5

+0.05%

+0.25%

waveforms

2/

l-u--L

0.2 Hz to 20 Hz
2 Hz to 200 Hz
20 Hz to 2 kHz

200 Hz to 20 kHz
2 kHz to 200 kHz

20 kHz to 2 MHz

2/

selectable,

steps and over-

5Oa

load) controlled

V signal. Voltage

for 10 minutes

for 24 hours

HORIZONTAL PRECISION

Dial Accuracy

*2%

of full scale, 1 Hz to 2 MHz

Frequency Vernier

One

turn equals 1% of full scale.

Time Symmetry

*I

% through XIOOK range

VERTICAL PRECISION

Sine Wave Frequency Response
Amplitude change with frequency less than:

dB

from 0.2 Hz to 200 kHz

0.1
dB

from 0.2 Hz to 2 MHz

0.5

PURITY

Sine Wave Distortion

Less than:

0.5% on X10, X100,

1.0% on XIOOK range
All harmonics 30

Square Wave Rise and Fall Time
Less than 50 ns terminated into

NOISE

outputs
Pseudo-random analog or digital noise with a maximum
of 20 V p-p excursion (open circuit) with 60
attenuator in 10

vernier.

Sequence Lengths
Push buttons on the front panel provide a sequence

length of

dB steps and overlapping calibrated

21° -

1, 215 - 1, or 220 - 1.

X1K, X10K

dB

down on Xl MHz range

ranges

SOQ

dB

step

1

lock

Noise C
Switchselectable noise

Clock Frequency

OPERATIONAL MODES

FUNC
form atthe main

S/N Signal-to-Noise operation adds noise to a selected
signal of constant amplitude. The signal-to-noise ratio
is variable from 0 to

N/S Noise-to-Signal operation adds a selected signal
to a constant amplitude noise. The noise-to-signal ratio
is variable from 0 to

FM Frequency Modulation - Provides random modu­lation of the frequency of the generator. The S/N

(dB)

quency deviation.

Frequency

160 Hz

1.6 kHz
16 kHz

160 kHz

1.6 MHz

Function

ratio control also controls the amount of fre-

frequencies

Mode

-

Provides the selected

output.

+60

dB.

+60

dB.

NOTE

are listed

Analog Noise

Bandwidth

10 Hz
100 Hz

1 kHz
10 kHz
100 kHz

-

N/S

ENVIRONMENTAL

Temperature
All specifications listed, except stability, are for

*5’C.

For operation from

specifications by factor of 2.

MECHANICAL

Dimensions

8%

incheswide,5% incheshigh,

Weight
8 Ibs net,

Power

105Vto125V

Less than 15 watts.

12 Ibs shipping

or

200

All

specifications apply for frequencies

obtained when dial is between 0.

2.0 and at 10 V p-p in to a 50 ohm load.

V

to

NOTE

O°C

250

to

V,

55’C,

derate all

11%

inches deep

50Hzto400Hz.

1

and

25’C

When noise is added to the signal output,
specifications apply up to 200
the square wave rise time is dera ted by

a factor of 10. In the clock range of

1.6 MHz, the maximum calibrated

to-noise ratio is 30

dB

kHz

and

signal-

It is possible to stop the generator from
oscillating by applying a negative VCG

voltage when the dial is already set at
minimum frequency. VCG inputs up to
30 V will not permanently damage the

ins trumen t.

INSPECTION

The following procedures should be performed to as­sure the user that the instrument has arrived at its
destination in satisfactory operating condition. Com­plete calibration and checkout instructions are pro­vided in Section 4 to determine compliance with elec­trical specifications.

Checking Visually

After carefully unpacking the instrument, visually in­spect the external parts for damage to knobs, dials,

indicators, surface areas, etc. If damage is discovered,
file a claim with the carrier who transported the in­strument. Retain the shipping container and packing
material for use in case reshipment is required.

Checking Electrically

NOTE

lnstrumen ts are normally shipped con­nected for 115 V power unless 230 V
power is ordered. Refer to the end of
this section for conversion instructions.

The steps in this paragraph provide a quick checkout
of the instrument operation. If electrical deficiencies
exist, refer to the WARRANTY in the front of this

manual. The following test equipment is recommended

for performing this electrical inspection:

Name Required

Oscilloscope

Plug-l n
Plug-l

n

Counter-Timer

1.

Turn

FREQ
(This connects ac power to the unit and estab­lishes the frequency multiplier.)

HZ selector to the Xl K position.

Characteristics

To 30 MHz

Dual channel
Peak mV measuring
capability
To 2 MHz with 5-digit
resolution

SECTION

OPERATION

2.

Depress MODE - FUNC push button.
Connect oscilloscope to the

3.
tor with a

Set frequency dial to the 1.0 mark and

4.
VERNIER to CAL position.

Set function selector to the

5.

Set OUTPUT

6.

NIER
tion (no attenuation).
Check for 1 kHz sine wave with at least 10 V

7.
p-p amplitude on oscilloscope.

Select

8.
and check for 10 V p-p amplitude on oscil­loscope.

9.

Turn frequency dial from maximum counter­clockwise (ccw) to maximum cw position and
check for frequency change.

10.

Step OUTPUT

its range and verify attenuation at each step.

11.

Rotate OUTPUT VERNIER
maximum cw to maximum ccw position and
check for decreasing amplitude.
Rotate

12.
frequency change.

13.

Set FREQ VERNIER control at maximum cw
and frequency dial at 0.02. Set frequency to

20 Hz with counter. Connect a 0 to +5 Vdc
input to the VCG IN connector. Slowly increase

voltage input from 0 to +5 V and check that
frequency of output waveform increases from
approximately 20 Hz to 2 kHz.

14.

Depress SEQUENCE LENGTH
button.

Set NOISE FREQ HZ selector to the

15.
position and vernier control fully cw.

Connect a BNC cable from the NOISE SYNC

16.

connector (rear panel) to the external trigger

input of the oscilloscope.
Rotate the function selector to

17.

to assure oscilloscope displays digital noise.
Check to assure SEQUENCE LENGTH push

18.
buttons vary the bits in the sequence length.

19.

Step NOISE FREQ HZ selector through its
range and check to assure clock frequency
changes. (Use NOISE CLOCK connector on rear
panel.)

5Oa

terminator.

ATTEN

(dB)

to maximum clockwise

2/

and s with function selector

ATTEN (dB)

FREQ

VERNIER control and check for

5Ofi

(dB) and OUTPUT VER-

selector through

(dB)

m

OUT connec-

FREQ

yj

position.

(cw)

posi-

control from

2l* - 1

push

16K/160K

and check

l

3

Verify that NOISE FREQ HZ vernier control

20.
provides approximately IO: 1 variation in clock
frequency at the NOISE CLOCK connector
(rear panel).
Rotate function selector to

21.
check to assure oscilloscope displays analog
noise.
Check to assure SEQUENCE LENGTH push

22.
buttons vary the length of the sequence of
analog noise. (Use NOISE SYNC connector on
rear panel.)
Connect oscilloscope external trigger cable to

23.

FUNCTION SYNC connector (rear panel) and
set function selector to
Set S/N - N/S

24.
and vernier control fully ccw.
Depress MODE

25.
to assure square waveforms are frequency modu­lated by analog noise.
Release MODE

26.
MODE
square wave and analog noise are mixed.

27.

Depress MODE

-

N/S

S/N
position, checking for reduction in signal level.

28.

Verify that the S/N
ates the signal approximately 10
each step of the S/N

OPERATING CONTROLS

The operating controls and electrical connections for
the Model 132 are shown in Figures
of the following paragraph numbers corresponds to a
number appearing in Figure 2-1, front panel, or
Figure 2-2, rear panel. The listing below discusses each
control and its function.

FRONT PANEL

1.

FREQ HZ/PWR OFF - Selects one of six dec­ade ranges from X 10 to
frequency.
quency dial setting (3) gives the output frequen­cy of the generator. Extreme ccw rotation will
place the switch in the PWR OFF position, turn­ing off all power to the function and noise
generators. This control has no affect on the
noise frequency.

FREQ VERNIER - Allows precision electronic

2.
control of the signal output frequency. A full
turn of the control is approximately equal to 1%

(dB)

selector to -10 position

-

FM push button and check

-

FM push button and depress

-

S/N push button. Check to assure

-

N/S push button and rotate

(dB)

selector ccw through each

This value multiplied by the fre-

/‘=ltif’

I

_I

position.

-I

-

N/S

(dB)

vernier attenu-

-

N/S (dB) selector.

2-I

X1M

for generator

position and

dB

between

and 2-2. Each

of full scale. When turned to the full cw position
(CAL), settings on the main dial will be cali­brated.

-

Frequency Dial
signal output frequency.

Frequency Index
setting (3) by reading the dial position opposite
the scribe line on the frequency index. The in­dex is illuminated when power to the unit is on.

Function Selector
or noise output. To select
waveforms, or J/-IL_ or
push button (7) must be depressed.

OUTPUT VERNIER (dB)
control of 0 through -20
ATTEN (dB)
justment for the output signal and will attenuate
signal and noise.

MODE

FUNC - When depressed, this control allows
the selected waveform or noise, as determined
by the position of the function selector (5), to

be present at the
This push button must also be in the depressed
position for the frequency modulation mode

(10).

S/N - Depressing this push button allows a
calibrated amount of analog noise to be added
to the selected signal, either

r

wave. The signal-to-noise ratio (S/N) is
determined by the S/N
control (13). When in this mode, the peak to
peak signal amplitude is reduced internally, since
adding noise to the signal would overdrive the
output amplifier.

-

Depressing this push button allows a

N/S

calibrated amount of the selected signal, either

i

L

Ad

analog noise. The noise-to-signal ratio (N/S) is
determined by the S/N
control (13). When in this mode, the peak to
peak signal amplitude is reduced internally, since
adding the signal to the noise would overdrive
the output amplifier.

Allows coarse control of the

-

Indicates the frequency dial

-

Selects the desired function

‘1,

,

/‘-‘iv‘

noise, the FUNC

-

Provides vernier

dB

from the OUTPUT

setting (12). This is the fine ad-

5Oa

OUT connector (11).

-

N/S (dB) attenuator

, or

wave, to be added to the

‘L

-

N/S (dB) attenuator

i*\./

2/

,

, or

2/

I,

, or

4

7

I

WAVETEK

Figure 2-l. Operating Controls, Front Panel

10.

FM - Depressing this push button along with
the FUNC push button (7) allows the selected
signal, either

/‘\

u

, v

A

,

or

z

pseudo-randomly frequency modulated, or jit­tered. The modulating signal is provided by
pseudo-random analog noise, and the S/N
N/S

(dB)

controls frequency deviation. The

bandwidth of the modulating signal is controlled

FREQ

by the NOISE

HZ selector (15) and

vernier (16).

11.

5Oa

OUT - Provides the selected generator out­put function. The generator may operate into an
open circuit providing 20 V peak to peak maxi-

5Oa

mum, or into a

load providing a

to peak output.

12.

OUTPUT

ATTEN

(dB) - Attenuates the output

(both signal and noise) from 0

dB

six calibrated 10

steps according to the fol-

lowing table:

wave, to be

10

dB

to -60 dB in

V peak

, ,,

MO~EI..

VCG!NQISE

Step

132

GENERATOR

Output peak to peak into

Attenuator

Position

Maximum Minimum

Vernier Vernier*

fully cw

­dB

0

dB

-10

-20

dB
dB

-30
dB

-40
dB

-50
dB

-60

10V

3V

IV 0.1 v

0.3 v 0.03 v

0.1 v

0.03 v 0.003 v

0.01 v 0.001 v

* The values in this table are approximate. The OUT-

(dB)

PUT VERNIER
approximately 20

S/N

-

13.

N/S (dB) - I n

(6) will reduce the output

dB

in all cases, as shown.

the S/N

mode, this control

attenuatesthe analog noise from

dB

five calibrated 10

steps. The selectable signal

0.01 v

0 to

5Ofl

IV

0.3 v

-50 dB in

Load

5

amplitude remains constant, thus giving cali­brated 0 to -50

N/S

mode, the signal is attenuated with the

noise remaining unchanged, thus giving
to-signal ratios from 0 to -50
this control are indicated in black numerals
the front panel.

14.

15.

16.

17.

-

S/N
fine adjustment of the S/N
tenuator (13). This control is continuously vari­able over at least a 10
the coarse control
total S/N or N/S ratio. Approximate values of
attenuation are indicated in red numerals on the
front panel.

NOISE FREQ HZ
the clock frequency, or bandwidth for the digi­tal, or analog noise, respectively. When using the
digital noise function, clock frequencies from

160 Hz through 1.6 MHz (indicated in black

numerals and letters on the front panel) are
available. When using analog noise or the S/N,
N/S modes, the bandwidth of the analog noise
may be selected from 10 Hz to 100 kHz (in­dicated in red numerals and letters on the front
panel). In the FM mode, this control establishes
the bandwidth of the analog noise used for fre­quency modulation. There are four detent posi­tions with an overlapping vernier control (16).
With the vernier in the full cw position, the
clock frequency, or bandwidth, is equal to the
value printed to the right of the detent mark.

NOISE FREQ HZ Vernier

number 15, this control provides a continuous,

fine control between the detent positions of

thecoarse control. When in the full cw position,

the clock frequency, or bandwidth, is equal to

the value appearing at the right of the detent

mark. As the knob is rotated ccw, the clock
frequency, or bandwidth, is decreased. In the
full ccw position,the actual value will be at

least 10: 1 (and as much as 100:
the value to the right of the detent mark.

VCG IN
age control of function generator frequency. Up

1000:1

to
A positive voltage increases frequency and a
negative voltage decreases frequency. Refer to
“Operation as a Voltage Controlled Generator.”

dB

signal-to-noise ratios. In the

dB.

N/S (dB) Vernier - Allows a calibrated

-

N/S

dB

range. When added to

(13),

this amount equals the

-

This range control selects

-

As mentioned in

-

This connector

frequency change may be obtained.

allows

noise-

The steps for

(dB)

1)

lower than

external volt-

on

step at-

SEQUENCE LENGTH

-

18.

19.

20.

REAR PANEL

21.

22.

23.

24.

1 - Depressing this push button will

21°

provide 1,023 counts of the selected clock fre­quency,

NOISE
generation of a digital, or analog noise pattern.
At the end of each sequence, the pattern is
automatically repeated.

215

provide 32,767 counts of the selected clock
frequency,
NOISE
generation of a digital, or analog noise pattern.
At the end of each sequence, the pattern is
automatically repeated.

220 -

provide
frequency,
NOISE FREQ HZ controls (15 and
generation of a digital, or analog noise pattern.
At the end of each sequence, the pattern is
automatically repeated.

DC OFFSET
base line above or below ground

into
vertical symmetry. Peak amplitude is limited by
the dynamic range of the amplifier output.

FUNCTION SYNC
synchronizing signal output at the same fre­quency of the main generator; that is, at the
same frequency as the sine, triangle or square
wave. The amplitude is greater than 1 V peak to
peak square wave into open circuit at
output impedance.

NOISE SYNC
chronizing output signal for monitoring the dig-

ital or analog noise. A sync signal is generated at
the beginning of each repetitive cycle for the
selected sequence length of digital or analog
noise.

NOISE CLOCK
external output of the basic clock frequency
used to generate the digital sequence and analog
noise.

or bandwidth, determined by the

FREQ

HZ controls (15 and

-

1 - Depressing this push button will

or bandwidth, determined by the

FREQ

HZ controls (15 and 16), for

1

-

Depressing this push button will

1,048,575

5Oa

load). The OFF position gives normal

counts of the selected clock

or bandwidth, determined by the

-

This control adjusts the *5 V

-

This connector provides a

-

This connector provides a syn-

-

This connector provides an

(k2.5

16),

for

16),

for

V offset

6OOa

_

SAN OILGQ

l

CALfFORNfA

PAT. NO X268.738
OTHER

PAT

PEND.

MAN fp1 tt.S,A.

115

23OVAC 7htAMP

Figure 2-2. Operating Controls, Rear Panel

VAC

114

AMP

OPERATION

No preparation for operation is required beyond com­pletion of the initial installation previously stated in
this section. It is recommended that a one-half hour
warm-up period be allowed for the associated equip­ment to reach a stabilized operating temperature and
for the Model 132 to attain stated accuracies.

Operation as a Function Generator

1.

Terminate

5Oa

OUT connector with

5Oa *I%,

2 watt termination.
Select the desired waveform by setting function

2.
selector to

\

, 2/

,

or

?_1

,

Set frequency dial and FREQ HZ range multi­plier for desired output frequency.

-

Depress MODE

FUNC push button.
Select output signal amplitude by setting OUT­PUT

ATTEN (dB)

control to appropriate attenu­ation position and fine adjusting signal to de­sired amplitude with OUTPUT VERNIER

(dB)
control.
A positive or negative dc offset may be applied
to the waveform by setting the DC OFFSET

(Rear Panel) to the desired level. The peak

k5.0

signal value plus the offset cannot exceed

V

into 50 ohms.

Operation as a Voltage Controiled Generator

The VCG input connector can be used to externally
control the frequency of the generator. If a positive
voltage is applied to the VCG input terminal, the
frequency will increase from the dial setting, A nega­tive voltage will cause the frequency to decrease from

the dial setting. The VCG range of the Model 132 is

1000:1.

Terminate 5Oct OUT connector with 50 ohm

1.

+l%,

2 watt termination.

Select the desired waveform by setting function

2.
selector to
Set FREQ HZ selector to desired multiplier.

3.

4.

Connect external voltage source (dc program-

$

,

/YJ ,

or

‘1~

.

ming or wideband ac signal) to VCG IN con­nector.

NOTE

%

VCG input requires 0 to

volts for
operation over full-scale range, but can
withstand many times maximum input.

5.

Set frequency dial as follows:
a.

For frequency modulation with ac input, set
dial for center frequency.

7

b. For increasing frequency sweep with positive

dc input, set dial to lower frequency limit.

c. For decreasing frequency sweep with nega-

tive dc input, set dial to upper frequency
limit.

To sweep the audio range from 20 Hz to 20 kHz,

6.
set the controls to 20 Hz as follows:
a. Set the main dial to 0.02.
b. Set the frequency vernier to the full ccw

position.

c. Introduce a 0 to +5 V ramp into the VCG

inputconnector.

The maximum frequency which may be obtained, when
using the VCG input, is the range multiplier times the
value at the top of the dial (2.0). The minimum fre­quency is the range multiplier times the value at the
bottom of the dial (0.002
be in ccw position). Verify this using the nomograph

in Figure 2-3.

MAIN DIAL

SETTING

A

Figure 2-3 - VCG Voltage-to-Frequency Nomograph

-

frequency vernier must

VCG IN

VOLTAGE

B

5Ofi

OUT

FREQUENCY

.4

1.6

1.8

2.0

C

.02

.2

.6

.8

In example 1, the dial is set at 1.0 and 0 voltage is

applied to the VCG input. Extend a straight line from

1.0 (dial setting) through 0 voltage (VCG voltage) and
obtain a dial frequency of 1.0. For the total output
frequency, multiply the range by 1 with the same dial
setting. Example 2 shows the results of using a ramp

+2.5

from -1 volt to
results in a swept output from 0.6 to 2.0 on the dial.

Remember to multiply the dial times the range.

Operation as a Calibrated Signal-to-Noise Source

1.

Select the desired signal waveform by setting
function selector to

2.

Set frequency dial and FREQ HZ range multi-

plier for desired signal output frequency.

3.

Depress MODE - S/N push button.

4.

Select noise bandwidth by setting NOISE FREQ

HZ control to desired range and fine adjusting

bandwidth by turning the noise frequency Hz
vernier control.
Select desired SEQUENCE LENGTH by de-

5.
pressing appropriate push button.

Select signal-to-noise ratio by setting S/N - N/S

6.
(dB) control to appropriate attenuation position

and fine adjusting attenuation to desired value
with S/N

7.

Select total output amplitude by setting OUT-

ATTEN (dB)

PUT
uation position and fine adjusting signal to de­sired amplitude with OUTPUT VERNIER (dB)
control.

Operation as a Calibrated Noise-to-Signal Source

Select the desired signal waveform by setting

1.

function selector to

2.

Set frequency dial and FREQ HZ range multi­plier for desired signal output frequency.

3.

Depress MODE

4.

Select noise bandwidth by setting NOISE FREQ
HZ control to desired range and fine adjusting
bandwidth by turning the noise frequency Hz
vernier control.

5.

Select desired SEQUENCE LENGTH by depres­sing appropriate push button.
Select noise-to-signal ratio by setting S/N

6.
(dB) control to appropriate attenuation position
and fine adjusting attenuation to desired value
with S/N

Select total output amplitude by setting OUT-

7.

ATTEN

PUT
uation position and fine adjusting signal to

volts for the VCG voltage. This

\

,

2/

, or

-

N/S vernier control.

control to appropriate atten-

Q

,

2/

, or

-

N/S push button.

-

N/S vernier control.

(dB) control to appropriate atten-

-

z

z

N/S

de-

.

,

sired amplitude with OUTPUT VERNIER (dB)
control.

Operation as a Random FM Source

Before using the generator as a random FM source,
please note the following.

Select desired SEQUENCE LENGTH by depres-

4.
sing appropriate push button.

5.

Select noise amplitude by setting OUTPUT
ATTEN

(dB) control to appropriate attenuation

position and fine adjusting noise to desired

amplitude with OUTPUT VERNIER (dB) con-

trol.

The frequency of the generator is being varied or

modulated by a changing voltage in the same way as
described in “Operation as a Voltage Controlled Gen­erator.”However, instead of using a dc ramp, or ac
signal, a random analog voltage is used. When the FM
push button is depressed, the analog noise is injected
internally into the VCG circuit; therefore, the modu­lation is created by random noise. The S/N
knob controls the maximum amount of frequency
deviation, since it controls the amplitude of the noise.
Bandwidth of the FM signal is controlled by the
NOISE FREQ HZ control. Using the generator in the
FM mode may be accomplished as follows:

1.

Select the desired signal waveform by setting
function selector to

2.

Set frequency dial and FREQ HZ range multi­plier for desired center output frequency.
Depress MODE

3.
Select the bandwidth by setting NOISE FREQ

4.
HZ control to desired range and fine adjusting
frequency by turning the noise frequency Hz
vernier control.

5.

Select desired SEQUENCE LENGTH by depres­sing appropriate push button.

Select signal frequency deviation by setting

6.

7.

-

N/S

(dB)

S/N

tion position and fine adjusting attenuation to
desired deviation with S/N
Select output signal amplitude by setting OUT-

ATTEN

PUT

uation position and fine adjusting signal to de­sired amplitude with OUTPUT VERNIER
control.

control to appropriate attenua-

(dB) control to appropriate atten-

‘b

, 2/ , or

-

FUNC and FM push buttons.

-

N/S vernier control.

-

N/S

(dB)

‘1J .

(dB)

Connect Signal and Chassis Grounds

The instrument is shipped from the factory with the
signal ground floating above chassis ground, unless
otherwise specified. A common signal/chassis ground
can be obtained as follows:

1.

Remove power cord.
Loosen two captive thumb screws on rear panel

2.
and remove panel.

3.

Solder a jumper wire between the ground lugs

(green wires) of the SYNC OUT connector and

the power connector (Figure 2-4).

ADD
JUMPER

A/

POWER
TRANSFORMER OUT
T1

POWER
CONNECTOR

SYNC

CONNECTOR J3

J1

BRACKET

DC OFFSET
R

172/SW4

Operation as a Digital or Analog Noise Source

1.

Set function selector to digital or analog noise
position.

2.

Depress MODE
Select clock frequency for digital or bandwidth

3.
for analog noise by setting NOISE FREQ HZ
control to desired range and fine adjusting fre­quency by turning the noise frequency Hz ver­nier control.

-

FUNC push button.

Converting Output Impedance to 600 Ohms

Unlessotherwise specified, this instrument was shipped
with 50 ohm output impedance, but can be converted
to 600 ohm output if needed. Place a

in series with the wire leading from the center tap of

the

Figure 2-2. Common Ground Connection Diagram

55Oa

resistor

5Ofi

OUT BNC and the attenuator control.

9

Converting to

instruments are shipped from the factory with the
power transformer connected for
unless ordered for 230-volt use. Converting a 115-volt
unit for 230-volt operation is a simple matter.

1.

230-Volt

Remove power cord.

Line Power

1 15-volt

line power,

2.

Loosen two captive thumb screws on rear panel
and remove panel.
The conversion switch is located on the chassis.

3.
Use a thin-bladed screwdriver to move the 115­230 switch to the 230 position.

4.
of the same type.

Replace

1/4-ampere

fuse with a

1/8-ampere

fuse

10

SECTION

3

CIRCUIT DESCRIPTION

GENERAL DESCRIPTION

Refer to the block diagram of the Model 132
Noise Generator, Figure 3-l.

Basically, a square wave is applied to the input of an
integrator composed of a wide-band differential dc

amplifier, integrating resistor and capacitor. Output

VCG/

VCG

VCG

Cl RCUIT

POWER

SUPPLIES

<

I

+5

v

+15 v

-15 v

I

DIGITAL

I

FILTER

I
I

I
I

HYSTERESIS

OUTPUT

SWITCH

.

+

CONVERTER

23

SINE

of the integrator is fed into the hysteresis switch.
The hysteresis and output switches function like a
Schmitt trigger with the limit points set at the
form extremes, firing when the triangle wave reaches
+1.25

volts and-1.25 volts. When firing occurs, the
hysteresis and output switches are set, reversing the
square wave fed into the integrator. Reversal of the
square wave causes the triangle wave to reverse direc-

wave-

FUNC

)

SYNC

OUT

x

L

I

.

MODE

%

L

r

b
b

SWITCHING

c

CIRCUIT

ATTENUATOR

9

4

t

I

--~-~---~---

-_-

Figure 3-l. Functional Block Diagram

.

NOISE

l

SYNC

b

NOISE

CLOCK

11

tion. The result is simultaneous generation of a square
wave and triangle wave of the same frequency with
the positive half cycle of the square wave coincident
with the negative slope of the triangle wave.

The magnitude of the capacitor across the integrator
and amplitude of the current into the integrator deter-

mine the frequency of oscillation. Capacitance across

the integrator is changed by rotating the frequency Hz

selector. Amplitude of the current into the integrator
is determined by four parameters which are summed

(1)

in the VCG circuit:
the frequency
voltage, (4) the VCG analog voltage input and (5) the
analog noise when in the FM mode.

The sine wave is produced by feeding the triangle
wave into a shaping network composed of resistors
and diodes. As the triangle wave voltage passes through
zero, loading of the triangle wave is minimal and thus
the slope is maximum.As the triangle voltage in­creases, diodes with current limiting resistors conduct
and successively cause the slope of the output to be

reduced.

Since the diode break points are mathematically com-

puted and fitted to the true sine shape, the resultant
waveform resembles a pure sine wave. Using a com­plementary pair of diodes on each break point, the
circuitry is completely symmetrical about ground. The
sine wave, produced by shaping, is considerably less

in amplitude than the triangle wave input and is thus
amplified to be equal to the triangle wave.

hysteresis switch output, (2)

dial

voltage, (3) the frequency vernier

Either square, triangle, or sine waveforms can be se­lected as a signal
from a digital filter. A clock oscillator of 160 Hz to

1.6 MHz range functions as a trigger source for the
digital pseudo-random sequence generator (P RSG).
Output of the PRSG is a random binary signal that
can function as digital noise. The number of bits in
each sequence can be selected by the SEQUENCE

LENGTH controls. Parallel data is fed from the PRSG
to the digital-to-analog converter where the informa­tion is summed and filtered to provide a random
analog noise signal.

The selected sine, triangle, square, analog noise,
digital noise signal is routed to the mode control
circuitry where one of the following modes of opera­tion is selected: Function
tion (FM); signal-to-noise (S/N)

(N/S). I n the signal-to-noise and noise-to-signal modes,
one signal is fed to the S/N attenuator and then mixed
with the other signal in the S/N summing amplifier in
a known

put of the mode switching circuit is coupled to the
output amplifier. From the output amplifier the signal

is fed to the precision output attenuator and finally to
a

All circuits, except for the hysteresis switch, output
amplifier, and PRSG, operate from
The hysteresis switch and power amplifier require

*6

PRSG requires a +5 V supply.

dB

5Ofl

output connector.

volts and

source.

The noise source is derived

(FUNC);

frequency modula

;

or noise-to-signal

ratio selected by the S/N attenuator. Out-

+I5

volt supplies.

*22

volts, respectively. Operation of the

or

12