Tektronix SW503 User manual

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SWEEP
GENERATaR
IIVSTFILICTION MAIti1L1AL

TABLE OF CONTENTS
Section 1

DESCRIPTION

Page
1 .1 INTRODUCTION

1-1
1 .2 ELECTRICAL
CHARACTERISTICS

1-1
1 .3 ENVIRONMENTAL CHARACTERISTICS

1-2
Section 2

OPERATION
2 .1 FRONT PANEL
CONTROLS AND CONNECTORS

2-1
2 .2 OPERATING
INSTRUCTIONS AND
NOTES

2-4
2 .2 .1 General Setup
and First-Time Operation

2-4
2 .2 .2 Cable
Connections

2-5
2 .2 .3
Impedance Matching

2-5
2 .2 .4 Detecting (Demodulating)

2-5
2 .2 .5 Sweep Rate Effects

2-6
2 .2 .6 Overloading Effects

2-6
2 .2 .7 Low-Level
Measurements

2-6
2 .2 .8
TV Receiver Interference

2-6
2 .2 .9 Use with Digital Counter

2-6
2 .2 .10 Operation
with X-Y Plotters

2-6
2 .3 EXTERNAL
CONTROL

2-7
2 .3 .1 Frequency Control

2-7
2 .3 .2 Amplitude Control

2-7
2 .3 .3 Trigger Control

2-7
WARNING
The
remainder of this table of contents refers to
servicing instructions which
should be performed by
qualified
personnel only .
Section 3

CALIBRATION
3 .1 INTRODUCTION

3-1
3 .2 EQUIPMENT REQUIRED

3-1
3 .3 PRELIMINARY STEPS

3-2
3 .4 PROCEDURE

3-2
Section 4

CIRCUIT
DESCRIPTION
4 .1
GENERAL

4-1
4 .2 SWEEP RAMP
GENERATOR

4-1
4 .2 .1 Basic
Operation

4-1
4 .2 .2
Ramp Generator

4-2
4 .2 .3 Single Sweep

4-2
4 .2 .4 Line Rate

4-3
4 .2 .5 CW Mode

4-3
4 .2 .6 MANuaI Mode

4-3
SW 503

S W 503
OPTIONS
TABLE OF CONTENTS
(cont)
Section 4

CIRCUIT DESCRIPTION (cont)

Page
Section 5

IMPLEMENTING SPECIAL FEATURES
Section 6

REPLACEABLE ELECTRICAL PARTS
Section 7

DIAGRAMS
AND CIRCUIT BOARD ILLUSTRATIONS
Section 8

REPLACEABLE MECHANICAL PARTS
CHANGE INFORMATION
4 .3 SWEEP DRIVE
CIRCUITRY

4-3
4 .3 .1 Input Adder

4-3
4 .3 .2 Ramp Shading Network

4-3
4 .3 .3
4 .3 .3 Output Amplifier

4-5
4 .4 SWEEP OSCILLATOR MODULE

4-5
4 .5
RF OSCILLATOR MODULE

4-5
4 .6 HARMONIC MARKER MODULE

4-7
4 .7 MARKER
AMPLIFIER

4-7
4 .8 COUNTER INTERFACE

4-9
5 .1
CHANGING HORIZONTAL OUTPUT VOLTAGE

5-1
5 .2 INTERFACE THROUGH REAR CONNECTOR

5-1
5 .2 .1 Introduction

5-1
5 .2 .2 Mainframe
Modification

5-1
5 .2 .3 Vertical
Output and Horizontal Output

5-1
5 .2
.4 External Frequency Control or Modulation

5-2
5 .2 .5
External Amplitude Control or Modulation

5-2
5 .2 .6 External Trigger

5-2
5 .2 .7 Digital Counter Interface

5-3

LIST OF ILLUSTRATIONS
Page
Figure 1-1

SW 503 RFSweep Generator

Frontis
Figure 2-1

SW 503 Front Panel

2-2
Figure 2-2

Typical operating setup .

2-4
Figure 2-3

Typical resistive pads .

2-5
Figure 2-4

Basic
detector schematic diagram .

2-5
Figure 2-5

Errors from sweep rate effects .

2-6
Figure 2-6

Markers selection switch location .

2-6
Figure 2-7

External control of frequency .

2-7
Figure 2-8

External control of amplitude .

2-7
Figure 3-1

SW 503 rear view .

3-2
Figure 3-2

SCOPE
HORIZ waveform
as
seen
on
test oscilloscope .

3-2
Figure 3-3

SW 503 adjustment locations, left side .

3-3
Figure 3-4

SW 503 adjustment and test points locations, right side .

3-4
Figure 3-5

Normal
interconnections for calibration .

3-4
Figure 4-1

SW 503 sweep ramp generator
(simplified diagram) .

4-2
Figure 4-2

Ramp shaping network .

4-4
Figure 4-3

RF sweep oscillator module block diagram .

4-5
Figure 4-4

Harmonic comb markers block diagram .

4-6
Figure
4-5

Counter interface signals sequence .

4-8
Figure 5-1

Rear plug-in connector P40 interface wiring .

5-2
LIST
OF
TABLES
Table 5-1

Digital Counter Interface Lines

5-3
SW
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' DESCRIPTION
1 .1
INTRODUCTION

Frequency Sweep
The SW 503 is a TM 500-Series plug-in that provides a
swept frequency of 1 MHz to 400 MHz
with variable sweep
rate,
width, and output level . Crystal-controlled harmonic
oscillators provide comb markers with 1 MHz, 10 MHz, or
50 MHz separation . When used with a DC 502 Option
7
Digital Counter, a frequency markerdot can be
positioned
anywhere within the frequency
range of the SW 503
generator, and the frequency
of the marker can be read
directly on the
counter . In the MANuaI sweep and CW
'

modes,
the continuous wave output of the generator can
be
read to the counter accuracy .
Access
jacks on the front panel permit external signals
to
control or modulate the output amplitude and frequen-
cy, and to initiate a sweep .
The SW
503 has a 50 f2 output impedance ; the SW 503
Option 1 has a 75 f2 output impedance .
Harmonic Related Spurii : Down 30 dB or
more from
10 MHz to 400
MHz ; 20
dB
or more from 3 MHz to
1 .2
ELECTRICAL CHARACTERISTICS

10 MHz ; and 15 dB or
more from 1 MHz to 3 MHz .
The following
characteristics apply when the SW 503,
in
combination with a TM 500-Series power module, is

Non-Harmonic Related Spurii : Down 40 dB or more
operating within an ambient temperatureof0°Cto+50°C,

froml
MHzto400MHzfundamentalfrequencyrange .
after a 30 minute or more warmup period .
Output Level
'

The instrument mustbe calibrated at an
ambient
temperature between+20° C and+30°
C .
Center Frequency
Dial Accuracy : Within 8 MHz (readout accuracy can be
increased by using the
crystal markers or
comb, or the
dot marker when the SW 503 is
used with a DC 502
Option 7 Digital Counter)
.
'

Drift : <100 kHz/5 minutes and <2 MHz/8 hours
after a

Step

Attenuator

Absolute

Ac-
"

30-minute warmup at a constant
ambient temperature ;

curacy

(with

respect

to

zero
a 5-minute stabilization
period is required after the

attenuation) : t0 .2 dB/10 dB to a
'

center
frequency is changed .

maximum of ±1 .0 dB .
NOTE
Range : 1 MHz to 400 MHz or more .
Maximum Width : Selectable ;
400 MHz (+10% - 0%)
Variable :
Permits reducing sweep width from maximum
dca+aose tt3 ag¢XOximatety
2QQ kHz {+nrhe~ in 1Q [+ttHz
maximum
width position)
Display Linearity (VAR fully clockwise) :
400 MHz position : 2%
100 MHz position : 3%
10 MHz position : 3%
Signal
Purity
Section 1-SW 503
Residual FM : 10
kHz p-p or less in cw position .
RF OUT :

Maximum output is approximately
0 .7 V rms . This corresponds to
+10 dBm ±0 .5 dB into 50
C2, or
+57 dBmV ±0 .5 dB into 75 f2 (Op-
tion 1) .
Output level can be attenuated
50 dB in 10 dB steps, and
20 dB by
avariable
attenuator . This
provides a
range from +10 dBm to
-60 dBm

for

the

SW 503,

or
+57 dBmV

to

-13 dBmV

for
SW 503 Option 1 .

Description-SW 503
From-250 mV to +250 mV (500 mV p-p ±5%) with an
output impedance of 1 kS2 . An internal resistor can be
AUX RF output : -2 dBm minimum into 50 O termina-

removed to change the output to approximately 10 V
tion (same for Option 1) .

peak-to-peak

with

an

impedance

of

20 kS2 . (See
Subsection 5 .1 for instructions .)
BLANKING
Output is blanked during sweep retrace . Blanking is
removed for manual and cw operation .
Frequency Markers (Harmonic Comb)
CAL (variable attenuator) : Con-

Sweep Times :

10, 1, 0 .1, and 0 .01 seconds per
tinuously variable

to 20 dB

sweep, ±5%, in decade steps .
minimum .

Variable control slows each step
by a factor of at
least ten from
its
Flatness : Within 0 .5 dB peak-to-

calihrated position .
peak over the frequency range .
Flatness is measured with the AUX
RF output terminated into 50 S2, at
maximum output,
and with
detec-

Horizontal Output
for (optional accessory), and in-
cludes harmonics .
Crystal-controlled harmonic markers with 1 MHz,
10 MHz,
or 50 MHz separation . Marker width is ad-
justablewith the MAX SWEEP WIDTH
VARiablecontrol
from about 400 kHz to 50 kHz and the marker
amplitude is adjustable with the SIZE control from
about 1
mV to 1 V peak-to-peak . If desired, an internal
switch will remove the negative portion of the marker
for use with an X-Y recorder .
Marker size is about 0 .5 V .
Marker Accuracy : 0 .005% of marker selected .
External Frequency Control
The full frequency range can be controlled or

,
modulated at rates to 4 kHz . Modulation sensitivity is
approximately 50 MHz/volt . With reduced deviation
and linearity, modulation rates to 100 kHz are possible .

r
Input impedance is 10
kf2 .
External Amplitude Control
90% modulation can be obtained at modulation fre-
quencies up to 25 kHz ; the output level must be
reduced 6 dB or more by the variable attenuation
control
.
Sensitivity is
about 1
V peak-to-peak per 10%
of amplitude modulation
.
Input impedance is 10
ks2 .
Functional only when DC 502 Option 7 Digital Counter

1 .3
EjIVVIRONMEWTAL CHARAC-
is used with the
SW 503 .
The dot marker can
be
adjusted over the frequency span of the display ;

TERISTICS
accuracy of the dot frequency is relative to the display
resolution and the counter accuracy . The sweep is

Temperature Range :
interrupted
at the dot position, a count is made, then the
sweep continues .

Operating Range : 0° C to +50° C .
Non-Operating : -40° C to +75° C .
Sweep Mode/Time
Ambient Temperature During ,
Modes :

CW, manual, timed sweep,
line

Calibration : +20°C to +30°C .
triggered . When in one
of
the timed
sweep speeds, the sweep is either
free-running, or can be triggered

Altitude Range :
by a front-panel button or an

Operating Range : To 15,000 feet .
externally-applied pulse or switch
closure .

Non-Operating : To 50,000 feet .

2 .1
FRONT-PANEL CONTROLS
AND
v SWEEP MODE/TIME
This switch selects CW, MANuaI, a timed sweep, or
LINE synchronized sweep .
r

CW position :

The SW 503 produces a cw output
whose
frequency is dependent
upon
the CTR FRED control set
ting (and EXT CONTROL, see 17) .
When a timed position is selected,
the VAR control can
beused to slow the sweep by a factor of
about ten from its
calibrated setting . A timed
sweep is recurrent but can be
manually
or externally
triggered by pulling the VAR
control out (see 3 and 17) .
TRIG
OPERATION
CONNECTORS

These pushbuttons select
crystal-controlled harmonic
Refer to Figure 2-1 for locations .

(comb)
markers with frequency spacings of 1 MHz,
10 MHz, or 50 MHz . The markers are applied to
the
SCOPE VERT connector and are mixed with the detected
input from the device under test .
MARKERS
NOTE
Section 2-SW 503
An internal switch removes the negative-going por-
tion of the markers,
which is often desirable when
using the
SW
503 with an X-Y recorder . See Subsec-
tion 2 .2 .10 .
MARKERS SIZE
MAN position :

The SW 503
provides an output

This control varies the amplitude of the comb markers
whose
frequency is dependent

from about 1 mV to 1 V peak-to-peak
.
upon the CTR FRED setting, and
the setting of the VAR control (also
the settings of the MAX SWEEP
WIDTH controls, see 8
and
9) .

When the SW 503 is used with a frequency counter
with
sweep stop logic such as the DC 502 Option 7,
this control
Timedsweep

positions an intensified frequency
markerdot anywhere
on the display .
The frequency of the dot position is then
positions :

The timed sweep positions are 10,

read out on
the DC 502 with digital counter accuracy . See
1, 0 .1, and 0 .01 seconds per sweep

Subsection 2 .2 .9 .
(when the
VAR control is set to its
fully
clockwise position) .
DOT POSition
LINE position :

In the LINE synchronized mode,

`J
CTR FREQ (Center Frequency)
the variable and single sweep
con-

This multiturn control selects the center frequency of
trots have no
effect .

the RF OUT signal .
NO
TE
li is
necessary to correlate the setting of the CTR
FREQ and MAX SWEEP WIDTH controls to avoid
"wrapping around" zero frequency .
MAX SWEEP WIDTH
Three pushbuttons select maximum sweep widths of
10 MHz, 100 MHz, or 400 MHz .
This pushbutton triggers the
sweepwhen the VAR
control is pulled
out (single sweep position) and the
SWEEP TIME/MODE switch is in one of the timed sweep
positions .

from the maximum selected sweep .
VARiable (MAX
SWEEP WIDTH)
The VARiable sweep width control reduces the width

Operation-SW 503
O
s
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r wsoFrnrE
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
i

i
13
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GTR fREn

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earw,
Figure Z-1 .
5W 503 front panel .
9
~s
ial
S
~1
1
1
1
1
I
1
1
"
1
1
1
1
1
1
1

~

OUTPUT
dBm (SW 503)or ATTENUATION

EXT CONTROL
dB
(SW 503 Option 1)
SW 503 :

This six-step control selects the rf

~

FREQ
output in 10-dB
steps from

This input
allows an external signal to frequency
+10 dBm to -40
dBm .

modulate or
control the output signal . Refer to Electrical
Characteristics, Subsection 1 .2, for
signal requirements .
Note that, when used with the
SWEEP MODE/TIME switch
SW 503 Option
1 :

This six-step control selects the rf

in

the

MANuaI

position,
the external control

is not
attenuation in 10-dB steps from

dependent
upon the settings of the MAX SWEEPWIDTH
0 dB to 50 dB
.
Maximum output

controls, whereas
the manual sweep control is dependent .
levels are from +57
dBmV to
+7 dBmV
.
The output is calibrated as indicated
when the CAL
control (see 11) is in its fully clockwise
position .
CAL
(VARIABLE ATTENUATION)
The CAL control adjusts the RF OUT
level to at least
20 dB below the level indicated
by the step attenuator .
RF OUT

(19)
TRIG
This connector provides a sweeping rf output
signal, at
a level selected by the attenuator
controls . The source
impedance is 50
S2
(SW 503) or 75
S2 (SW 503 Option 1) .
' ~

13

AUX
RF TERM 50
i1
This connector provides a
sweeping rf signal, for use
'

with a frequency
counter
or
other instrument . The output
level is at least -2 dBm and is independent of attenuator
settings . The source impedance is 50 O .
This connector allows returning the
demodulated rf
signal from the device under test (through an external
detector if necessary) for the
purpose of adding comb
frequency markers .
This connector is the output for the combined
demodulated rf (from DETECTED
INPUT) and comb
frequency
markers . The output is applied to the vertical
input of an oscilloscope or display monitor .
DETECTED INPUT
SCOPE VERT
SCOPE HORIZ
This connector is the output for the sweeping voltage
that is provided for application to the horizontal
input
of
an
oscilloscope or display monitor
.
Nominal
output
amplitude is 500 mV p-p ; an
internal wiring change will
provide 10 V p-p (See Subsection 5 .1 ) .
AMPL
+10 V
GND (Ground)
PWR (Power)
Operation-SW 503
This input allows an external signal to
amplitude
modulate or control the output signal
. Note that for
maximum
usefulness, the output amplitude must be
reduced 6 dB or
more by the VARiable attenuation
control .
Refer to Electrical Characteristics, Subsection
1
.2,
for signal
requirements .
When the VAR control is in the single
sweep position
(PULL for SINGLE
SWEEP), this input allows an external
signal to trigger the
sweep . The applied signal can be a
positive-going
pulse of up to 10 V amplitude and at least
1
~sduration,orcanbesuppliedbyaswitchclosure(solid
state or mechanical) to the
+10 V connector or similar
source .
This connector provides a convenient +10
V
source
to
facilitate using the above-mentioned
external controls .
This connector is connected to
ground on the circuit
board, to facilitate
using the above-mentioned external
controls, or for other signal ground purposes . DO
NOT
use this connector for safety earth
.
This indicator lamp shows
when power is applied to the
instrument .
2-3

Operation-SW 503
2 .2
OPERATING INSTRUCTIONS AND
NOTES
2 .2 .1 General Setup and First-Time Operation
Install the SW 503 in a
TM 500-Series power supply,
then apply
power
to
the unit, and allow instruments to
warm up .
OUTPUT dBm
(SW 503) or
Connect the SW 503 Sweep
Generator, the device

ATTENUATION dB
under test, and the oscilloscope
as shown in Figure 2-2 .

(SW
503 Option 1)

Maximum
(fully clockwise)
Refer to
the following sections for details and special

position
considerations .
CAL (output)

fully clockwise
After completing the setup, adjust the SW 503 controls
for the required center frequency, sweep width, and
output amplitude . If desired, turn the
markers on and
adjust their amplitude . For first-time
operation, set the
controls as follows :
SWEEP MODE/TIME

.01 s

A full specification check for the SW 503 is
included in
the Calibration Procedure,
Subsection 3 .4 . Refer,

r
VAR

fully clockwise

however, to the
warning page preceding Section 3 .
2051-3
2-4
SW503
RF

DET
o-'
OUT IN
HJ
MATCHING
I ,
DEVICE
I
~
NETWORK ,~ ~~J UNDER
/~, _~
DETECTOR I
TEST
L . _ _ _ J
I
I I___~___l
* if
necessary-see text
Figure 2-2 .
Typicaloperating setup .
CTRFRED

200 MHz
MARKERS SIZE

midrange
MARKERS frequency

50
MHz
MAX
SWEEP WIDTH

400 MHz
VAR (max sweep width)

fully clockwise
Connect the RF OUT through a
detector to the
DETECTED INPUT . Adjust the
oscilloscope or display
monitor vertical and
horizontal sensitivities for an on-
screen display .
Vary each of the above controls and note
its effect on
the the display .
VERT
IN
HORIZ
IN

Since hum, rf leakage, spurious signal
pickup, and

After the
sweep generator signal passes through the rf
.

standing waves must be kept to a
minimum, it is essential

circuit
of
the device under test, it must be demodulated
that good connections be maintained throughout the

before being connected to the DETECTED INPUT con-
entire setup . Use coaxial cables with bnc connectors

vector of thegenerator . If a demodulator is
nota part of the
wherever possible .
The RF
OUT cable
especially should

device under test, one must be added externally . The input
be kept as short as practical, and its impedance should

impedance of the demodulator must present the proper
match theoutput impedance of
the SW 503 . An idea of the

load

to

the

device

under

test .

Refer

to

Optional
integrity of the cabling can be obtained by connecting the

Accessories for recommended units, or see Figure 2-4
for
detector, through the cables, directly to the rf output

the basic schematic of a detector .
source, bypassing the device under test .
If the input impedance of thedevice under test is notthe
same as the sweep generator output impedance, a
matching network should be used to ensure
that a
constant amplitude versus frequency is sent to
thedevice
'

under test . This matching network can be either resistive
or
inductive ; the resistive matching pad is simpler to
construct than the balun type transformer, but it provides
more insertion loss . Figure 2-3 shows schematics for
several resistive matching pads . Note that the leads
connecting the 300 O output from the pad to the device
under test should be
as
short as possible, preferably less
than one inch .
75 TO SO S2

50f26dB
MATCHING PAD

PAD
2 .2 .2 Cable Connections

2 .2 .4
Detecting
(Demodulating)
2
.2 .3 Impedance Matching
56
50
i
.
O
150
37
230
75f26dB
PAD
150
50
d
50
TO
300 O

75 TO 300
IZ
MATCHING PAD

MATCHING PAD
2051-4
Figure 2- 3 . Typical resistive pads .
TERM
RESISTOR .

I

~
100k
100
Operation-SW 503
RF

DETECTOR
INPUT

OUTPUT
1k
Figure 2-4 . Basic detector schematic diagram .
2051-5

Operation-SW 503
2
.2 .5 Sweep Rate
Effects
When
sweeping rf circuits having rapid amplitude
changes, errors may
occur, due mainly todetectordelays .
Decreasing the detector output time constant will
minimize this effect . Figure 2-5
illustrates sweep rate
effect .
2-6
2 .2 .6
Overloading Effects
2 .2 .7 Low-Level
Measurements
TRUE RESPONSE
RESPONSE
WITH
SLIGHT
ERROR
DUE
TO
SWEEP
RATE BEING
SLIGHTLY TOO
FAST
RESPONSE WITH
LARGEERROR
DUE TO SWEEP
RATE BEING
FAR TOO FAST
Figure 2-5 . Errors from sweep rate effects .
To check for sweep rate effect, first set the
sweep
width
to its lowest practical amount, then increase sweep time
while closely
observing the swept output response . Any
change in the response indicates the sweep rate is too fast
for a true response . When a further increase of sweep time
does not change the response, a true response has been
obtained .
The use of excessive input signals to the device under
test can cause overloading . To assure that this condition is
not present, and that the response is a true representation
of the device under test, turn the OUTPUT dBm
(ATTENUATION dB on SW 503 Option 1) and CAL
controls to minimize output
amplitude
. Gradually increase
the output amplitude until a response is obtained . Further
increase of the output amplitude should not change the
configuration of the response envelope except in
amplitude . If the responseenvelopedoes change, such as
flattening
at
the
top, decrease the outputjust farenough
to
restore the proper configuration .
When making measurements at low levels, the effects
of radiation and ground loops may become problems .
Using
double-shieldedcables for rf signals helps minimize
the radiation problem . Ground
loops
causing
hum
pickup
can sometimes be eliminated by completing
only one
ground connection between each instrument . Thisapplies
particularly to the oscilloscope horizontal input . If the
ground connection is made at the vertical input terminal,
an additional ground at the horizontal input terminal will
often result in hum pickup .
2 .2 .8 TV Receiver Interference
When using the SW 503 with a tv receiver, interference
from
the
receiver's horizontal sweep circuit may
appear on
the response curve, making it difficult
to
observe
a
clearly-
defined trace . Therefore, we recommend that thetvsweep
circuit be disabled
during
testing .
2 .2 .9
Use
With
Digital Counter
The DOT POS control on the SW 503 functions only
when a digital counter with sweep interrupt logic, such as
the DC 502 Option
7, is
used with
the
system . In use, the
SW 503 sweep generating voltage is interrupted at the dot
position (positionable with the DOT POS control), and the
counter is told to initiate a count . At the conclusion of the
counter gate time, the sweep is resumed . The counter
provides an accurate indication of the SW 503 frequency
at
the dot location ; thedot
is
actually
caused by the sweep
remaining stationary during the count .
In order forthe DC 502 Option 7 to work properly, both
An internal switch (S510) in the SW 503 facilitates
operation with X-Y plotters
.
This
switch is
located on the
marker selection assembly directly
behind
the RF
OUT
connector (see Figure 2-6) .
zosi a
REFER TO TEXT,
SEC . 2 .2 .10
Measurement sensitivity will be determined by the type
of detector
used .

Figure 2-6 . Markers selection switch location .
units must be
installed m
specific compartments m
a
TM 500-Series power module equipped with Option 7 .
Thisoption adds
the wires necessary
to
interface the two
units via their rear-panel connectors . See Subsection 5 .2
for further information (also see warning page preceding
Section 3) .
2 .2 .10
Operation With X-Y Plotters
Fornormal operation, the switch is set toward the front
panel . For plotter operation, with theswitch set toward the
rear of the instrument, the high-frequency marker signals
are converted to a lower frequency (rectified) which is
compatible with the operating speed of the plotter pen or
styl us .

Frequency, amplitude, and sweep initiation can be
externally controlled through the use of the front panel
mini-pin jack connectors . These features can be used
singly or in any combination .
Functions of the front panel external control connec-
tors can be duplicated through the rear plug-in connector
by adding appropriate wires ; instructions to do this are
located in Subsection 5 .2
(also see
warning page
preceding Section 3) .
'

External frequency control may be achieved by apply-
ing a voltage between 0 V and +10 V to the FRED jack
(refer
to
Electrical
Characteristics, Subsection
1 .2, for
complete signal characteristics .)
.
For example, connect a
10 kf2
potentiometer to
the +10 V, GND,
and
FREQ
jacks
as shown in Figure 2-7 .
10 kQ
(linear
taper)
2 .3
EXTERNAL CONTROL

2 .3 .2 Amplitude Control
2 .3 .1 Frequency Control
2051-8
cw
TO
FREQ
TO
GND
Figure 2-7 . External control of frequency .
To
frequencymodulate the output, connect a source of
'

suitable voltage range and adjustable amplitude between
the GND and FREQ jacks .
Operation-SW 503
External amplitude control may be achieved in a similar
manner to frequency control (refer to Electrical
Characteristics, Subsection 1 .2, for complete signal
characteristics) . For example, to remotely adjust
the
amplitude,
connect a 10 kf2 potentiometer to the +10 V,
GND, and AMPL jacks as shown in Figure 2-8 .
zosl-s
cw
TO
+10 V
10 kS2
(linear

TO
taper)
AMPL
TO
GND
Figure 2-f3 . External control of amplitude .
To amplitude modulate the output, connect a source of
suitable voltage
range and adjustable amplitude between
the GND and AMPL jacks .
The most practical application of external amplitude
control is with the MANuaI or CW modes .
When the CAL
control is in its
calibrated position (fully clockwise),
applying +10 V will increase the amplitude approximately
5 dB, regardless of
the step attenuator setting . When the
CAL control is in its fully counterclockwise position (gain
reduced about 20 dB), applying +10 V will increase the
gain approximately 10 dB .
Remote frequency adjustment or modulation is possi-

2
.3 .3 TriggerControl
ble
in any
mode,
although the most practical application is

When the SWEEP MODE/TIME switch is in the 10, 1,
with the MANuaI or CW modes . The input to the FREQ jack

0 .1, or 0 .01 s sweep modes and
the VARiable control is
is summed with the SWEEP WIDTH selection and the
CTR

pulled
out
for single sweep, a sweep may be initiated by
FREQ selection (see Schematic Diagram) ; therefore,

applying
avoltage of
between about+2 V and +10 V to the
these settings interact .

TRIG jack . Two methods to accomplish this are :
a) Making a switch closure between
the TRIG and
NOTE

+10 V jacks ;
The greatest effect of a remotely-applied signal is

b) Applying a+10 V pulse between the TRIG and GND
realized when the SWEEP MODE/TIME switch is in

jacks . The pulse duration should be at least
1
Ns .
the MANuaI position, the VAR (manual sweep)
control is fully counterclockwise, the MAX SWEEP
WIDTH is set to 400 MHz, its VAR control is fully

The repetition rate of the applied signal
must
be
slower
' clockwise, and the CTR FREQ is adjusted for 1 MHz . than the sum of
the sweep plus recovery times .

Section 3-SW 503
CALIBRATION
r
3 .1
INTRODUCTION
To
ensure maximum performance,
the instrument should be checked after each 1000 hours of
operation
or every six months, whicheveroccurs first .
It should also be checked whenever repairs have
been
made .
This section
provides check and adjustment
information for calibrating the instrument to its
specification . We advise checking the performance, and
recalibrating only those circuits that do not meet
the specification
.
In general, adjustments
mustbe performed in the sequence
given, and while the instrument is
operating at an
ambient temperature of +20°C to +30°C after a
30-minute warmup period .
3z
EQUIPMENT REQUIRED
Po wer
Module
Plug-in extender cable
Display oscilloscope'
r

Test oscilloscope'
'

Detector
(SW 503)
Detector (SW 503 Option
1)
Power meter
75 52 to 50 52 minimum loss
pad (For Option 1 only
.)
'

Spectrum
analyzer
Digital voltmeter
TYPE

MINIMUM PERFORMANCE
REQUIREMENTS

EXAMPLES
X-axis, 50 mV/div ; Y-axis, 200 mV/div
.
1 MHz to 400 MHz coverage
.
0 .1% do voltage accuracy
.
'Although spoken of as separate
instruments in the procedure, these may be the same
instrument .
Tektronix
TM 500-Series
Tektronix 067-0645-01
Tektronix SC 502
Vertical sensitivity, 0 .1
V/div ;

Tektronix 5000-Series
sweep speeds 1 ms/div to 5 s/div
.
Triggered time base,
3% accuracy .
5052 input ; ±0
.3 dB from 1 MHz to 400 MHz .

Tektronix 118-0070-00
75 O input ; ±0 .3 dB from 1 MHz to
400 MHz .

Tektronix 118-0071-00
-10 and +10 dBm ±0 .5 dB
.

Hewlett-Packard 435A
Tektronix 011-0112-00
Tektronix 7L12 or
7L13
Tektronix DC
501 or DC 502

Calibration-SW 503
3 .3
Preliminary Steps
The following procedure exposes the technician to a
maximum potential of about 67 V do(±33 .5 V from
ground)
.
Take appropriate safety precautions . Refer
also
to Safety Notice
page at
the beginning of this
section .
Remove
the
SW 503 Plug-In from
the
mainframe,
remove its side covers, and reconnect it to
the mainframe
via the plug-in extender cable .
Turn the system power on and allow the units to warm
up for 30 minutes or more .
3 .a
PROCEDURE
WARNING
1 . Check/Adjust
Power Supplies
a . Connect the digital voltmeter between ground and
pin 2 of the Sweep Oscillator Module A20 (locate in
Figure 3-1) .
c . Adjust R405(FREQ) fora sweep time (positive-going
portion of waveform) of 10 ms, as
indicated in Figure 3-2 .
b . Adjust R310 (+18 ; locate in Figure 3-4) for a reading

See Figure 3-3
for adjustment location .
of +18 .00 V .

Z SW 503 sweep voltage output (SCOPE
HORIZ) is normally
500
mV p-p ; however, instruments have provision for changing the
sweep voltage to 10 V p-p (see Subsection 5 .1) .
zosi-
3-2
p
I I

'
1
O

I I

SWEEP
20110
GENERATOR
p

MODULE
3
O
10
O

A20
s0
K
U
W
Z
Z
O
V

O 4 O 3

MARKER
5O 2O

MODULE
O6 O
1

A10
c . Connect the digital voltmeter between ground and
pin 3 of Sweep Oscillator Module A20 (locate in
Figure 3-1), and check
for a reading of -18 .00 V ±0 .2 V .

-
d . Connect the digital voltmeter between ground and

'
the front panel +10 V jack, and check for a reading of
+9 .8V±0 .2V .
e . Connect the digital voltmeter between ground and
pin 3 of Marker Module A10 (locate in Figure 3-1 ), and
check for a reading of +5 V ±0 .2
V .
a .
Set the SWEEP MODE/TIME control to 0 .01 s, and
the VAR control fully clockwise .
2 . Adjust Sweep Generator
b . Connect the SW 503 SCOPE HORIZ to the test
oscilloscope
vertical input . Adjust the test oscilloscope
vertical sensitivity to 0 .1 V/div e and time base to 5 ms/div,
and adjust triggering and positioning for a stable
pattern
similar to Figure 3-2 .
i

i

i

i

I

i

i

i
___~___+___+___+___ I~___~___+___+___ .
+5V
I

I

I

I

I

I

I

I
I____J ___J____ L___
___Jr.___Jr___,L____~____ __

r
I

I

I

I

i

I

I
I

I

I

I

I

I

I

1
I

I

I

I

I

I

I

I
___~___+____I~___~

_ { ____~_
_ma r ___ i____~___
I

I

I

I

.

I

I

I
I

.

I

I

I

I
I

I

I

I
OV

i-

I
I

I

I

I

I

I

I

I
I

I

I

I

I

I

I

I
I

I

I

I

___ I

1

I

I
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
I_____
~____J____ _
____ ___~____r___
II
I
__+___
I

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
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
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
I

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
I
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__J____J_________
I

I____J___ J ___
__ ~___,_

I

~_____
-5V

I 1

1 I I
2osi-m
i

I

I

I

I
I
i

.

I

I

I

I

I

i
SWEEP

_
I~RETRACEi
TIME
TIME
WAIT TIME (LINE POSITION
ONLY)
~-16 ms@liOHz
20 ms@50
Hz
Figure 3-2 . SCOPE HORIZ waveform as seen on
test
Figure 3-1 . SW 503 rear view .

oscilloscope .

'

e . Return the VAR control
to
its fully-clockwise posi-
tion, and set the SWEEP MODE/TIME switch
to
LINE . Set
the test oscilloscope time base to 1 ms/div, and adjust
R435 (CLAMP) to clamp the base of the waveform to the
same amplitude as the waveform base in step c
(Figure 3-2) . See Figure 3-3 for adjustment location .
'

3 . Adjust Frequency
Calibration
a . Set the SWEEP MODE/TIME switch to CW, and the
f . Adjust R370 (WAIT) for a wait time of approximately
1
ms as indicated in Figure 3-2 . See Figure 3-3 for
adjustment location .
b . Connect the digital voltmeter
between ground and
-

U210A pin 1 (locate in Figure 3-4) .
2051-12
MODULE
A20
0
(75 Q units)
S510
Figure 3-3 . SW 503
adjustment
locations, left side .
Calibration-SW 503
. ....

iill
ATTENUATOR

. . . . .

(III
A30
MODULE
A10

,
d . Rotate the VAR control fully counterclockwise . The

d . Connect the SW 503 to the display oscilloscope as
sweep time should be 100 ms or greater (reduce test

indicated
in Figure 3-5, and set the
controls
as follows :
oscilloscope sweep time as necessary to check) .
SW503
SWEEP MODE/TIME

0 .01 s
(Sweep Time) VAR

Fully clockwise
CTR FREQ

200 MHz
MAX SWEEPWIDTH

400 MHz
VAR (Max sweep width)

Fully clockwise
50 MHz MARKERS

ON (pushed in)
MARKER SIZE

Midrange
OUTPUT dBm (50 O units) +10
ATTENUATION dB

0
CAL (output dBm)

Fully clockwise
CTR FREQ control to 200 MHz .

Display Oscilloscope
Mode

X-Y
Horizontal sensitivity

50 mV/div z
Vertical sensitivity

200 mV/div
Z SW 503 sweep voltage output (SCOPE HORIZ) is normally
C . Adjust R185 (BAL) for a voltage of zero on the digital

500 mV p-p ; however, instruments have provision for changing
voltmeter .
See Figure 3-4 for adjustment location .

the sweep voltage to 10 V p-p (see Subsection 5 .1 ) .
3-3

Calibration-SW 503
2051-13
3-4
TO
DC502
COUNTER
(optional)
DETECTOR
SCOPE
VERT
P40
LIN
0190
REF
O
f-Collector
SIZE SIZE
10/50

1 MHz

MiN ~a
FREO
0
400
MAX ~
~
F350

~
R
18
FRED

a FRED
200

300
FRED ~
U210
250 1
BAL
Figure 3-4 . SW 503 adjustment and test points locations, right side .
0
FRED
0 MHz
SW503

SC502
RF AUX DETECTED '
OUT

RF

INPUT

EXT HORIZ
I(

IN
HORIZ

l i
J
Figure 3-5 . Normal interconnections for calibration .
2051-1a

Calibration-SW503
To identify the frequencies shown on the resultant

4 . CheckSweep
Width
display,
the
markers must be positively identified . The
zero beat in the swept rf output
does
not vary
in amplitude

a . Press the 100 MHz MAX SWEEP WIDTH and 50 MHz
with the MARKERS SIZE control and looks distinctly

MARKERS buttons, and check that the sweep width is at
different than a marker ; therefore, it can be used as a

least 100 MHz . (That is, three markers visible . It may be
frequency reference . The first marker to the right of zero is

necessary to
vary
the
CTR FRED slightly .)
50
MHz, the
second marker is 100 MHz, and so on . The

b . Press the 10 MHz MAX SWEEP WIDTH and 10 MHz
frequency of each marker can be identified by referring to

MARKERS buttons, move the CTR FRED about 5 MHz as
thezero beat until the CTR FRED dial reading
is sufficient-

necessary, and check that the sweep is at least 10 MHz
ly calibrated .

(that is, two markers visible) .
e . Identify the 200 MHz marker, then reduce the
frequency sweep with the MAX SWEEP WIDTH VAR
control and adjust R235 (FREQ 200) to placethe marker in

5 . Check Frequency Dial Accuracy
the center
of
the
oscilloscope display . See Figure 3-4 for

a . Press the 400 MHz MAX SWEEPWIDTH and 50 MHz
adjustment location .
MARKERS
buttons .
f . Set the CTR FREQ control to 50 MHz and adjust R225
(FREQ 0 MHz) to placethe 50 MHz marker at thecenter of

b . Adjust the CTR FREQ control from
50
MHz
to
the oscilloscope display . See Figure 3-4 for adjustment

400 MHz and check that it reads within
±g
MHz
of a
location .

multiple of 50 MHz when each marker is centered .
g .
Reset the CTR FREQ to 200 MHz, and repeat steps e
and f until the interaction is minimized .
6 . Adjust Output Level
h . Set the CTR FREQ control
to 350
MHz
and connecta

a . Adjust the front panel controls as follows :
probe from the test oscilloscope to the junction of Q190
collector and CR196 cathode (locate in Figure 3-4) . Adjust
the test oscilloscope to display at least one cycle

CTR FREQ

100 MHz
(2 ms/div), and
adjust its vertical sensitivity for a
full-

SWEEP
MODE/TIME

CW
screen display, dc-coupled (>2 V/div) .
OUTPUT dBm (50 C2)

+10 dBm
i . Momentarily disconnect the probe, or switch the test

or
ATTENUATION
dB (75
S2)
0 dB
oscilloscope input to ground, and vertically position the
trace to center screen ; then reconnect the probe and

CAL (output dBm)

Fully
clockwise
adjust R195 (LIN REF) to center the displayed waveform
voltage to about
zero . See Figure 3-4 for adjustment
location .

NOTE
j . Set the CTR FREQ control
to 250 MHz, and adjust

For standard instruments with 50 S2 output, perform
R215 (FREQ 250) to
place the
marker at the center
of
the

steps b through e . For Option 1 instruments with
display . See Figure 3-4 for adjustment location .

75 S2 output, perform steps f through i .
k . Set the CTR FREQ to 300 MHz, 350 MHz, and
400 MHz respectively, and adjust the corresponding fre-

b~
Connect a power meter
to
the RF
OUT
connector .
quency adjustments (R210, R204, and R201) to place
the
correct marker at the center
of
the display . See Figure 3-4
for adjustment locations .

c . Adjust R240 (LEVEL MAX) for an output level of
+10
dBm . See Figure 3-4 for adjustment location
.
I . Set the CTR FREQ
control to 200 MHz, and MAX
SWEEP WIDTH
controls for 400 MHz (VAR fully

d . Set the CAL control fully counterclockwise, and
clockwise) .

adjust R245 (LEVEL MIN) for an output level of -10 dBm .
See Figure 3-4 for adjustment location .
m . Adjust R180 (SWEEP WIDTH) so that both the 0 Hz
and the 400 MHz markers are just visible at the ends of the

e
.
Rotate the CAL control
fully
clockwise, and repeat
sweep . See Figure 3-4 for adjustment location .

steps c and d to minimize interaction .

Calibration-SW503
f . Connect a
power meter (with 50
S2 input) through a

8 . Check Flatness
50 f2 to 75
O minimum loss attenuator
(Tektronix Part
Number 011-0112-00} to the
RF OUT connector .
g . Adjust
R240 (LEVEL MAX) for a
power meter
indication of
+2 .5 dBm .
h . Set the CAL control
fully counterclockwise, and
adjust R245 (LEVEL MIN)
for a power meter indication of
-17 .5 dBm .
i
. Rotate the CAL control fully
clockwise, and repeat
steps g and h to minimize
interaction .
a . Set the
CAL control fully clockwise and
note the
power meter reading
.
b .
Reduce the OUTPUT dBm or
ATTENUATION dB
control one step and check
for a 10 dB reduction on the
power meter
indication (within ±0 .2 dB per 10
dB steps,
maximum of
±1 .0
dB
overall) .
c . Reset the power meter range as
necessary and repeat
step b for all attenuator steps .
Preferably check both steps
of the output attenuator
on the same range of the power
meter to avoid
compounding tolerances .
3-6
a .
Connect the RF OUT through a detector (optional
accessory)
to the DETECTED INPUT and
set the controls
as
follows :
SWEEP
MODE/TIME

0 .01 s
CTR FRED

1 MHz
OUTPUT
dBm
or

Maximum output
ATTENUATION
dB
9 .
Check AUX RF Output Level
d . (Alternate Method) Connect
the RF OUT through a

a . Connect
the SW 503 RF OUT to the input of a
suitable rf step attenuator or
attenuator pads to a detector

spectrum
analyzer, such as a 7L12 or 7L13 .
(which is connected to
the DETECTED INPUT) .
MAX SWEEP WIDTH

10 MHz
CAL (Output dBm)

Fully clockwise
Display oscilloscope

50
mV/div, dc-coupled
vertical input
b .
Adjust the display oscilloscope vertical
sensitivity for

,
7 . Check Attenuator Steps

a
10-division display . To accomplish this,
since most
displays have only eight
divisions vertically, firstadjustfor
eight divisions using the
display oscilloscope variable
NOTE

attenuator control,
then reposition the display (not the

,
baseline) two
divisions toward the center, and readjust the
There are several ways
the attenuatorstep accuracy

variable
attenuator for two more divisions amplitude
.
could be
checked . Steps a through c below
outline
one method ; steps d through
e give an alternate

c,
Adjust the
CTRFRED throughout its range and
method .

check that
the vertical display remains within 0 .6
major
division . With the vertical amplitude set
as previously
shown, this corresponds to
0
.5
dB .
a .
Terminate the RF OUT,
connect a power meter to the
AUX RF connector, and
switch the SWEEP MODE/TIME

,
to CW .
b
.
Tune
the CTR FRED throughout
its range, and check
that the
AUX RF level is at least -2
dBm .
10 . Check Harmonics
and Spurious Signals
t
b . Set the SWEEP
TIME/MODE to CW, CTR FRED to
e .

Compare the difference in
the output when

1 MHz, and output to maximum .
attenuated by the internal
attenuator, to that when
attenuated by the external precision
attenuator . The
difference between the two
outputs is the attenuatorerror
.

c . Adjust the spectrum
analyzer to display the 1 MHz
Maximum
allowable error is 2%, not including
the basic

fundamental, with a
Span/Div of 100 MHz . Set
the
flatness or
vernier attenuator error . The detector
can be

Reference Level as low
as possible without overdriving,
used
at levels down to about -40
dBm ; at lower levels an rf

and position the top of
the fundamental to a convenient
amplifier or spectrum analyzer
must be used .

reference
line .