Tektronix SW503 User manual

TE NCT`Rt7IrV 1 ~~
sw~a~
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
503

5W SU3
srrESr
rron~rnrlr
'.,
,~~
w1A11

" ltl
sw
LIKE
CTII Film

,-ae,r

~
v "
2
3='-
Flgure
1-1 . 5W 503 RFSweep
Generator .
RS
OAT

All][ !!F

QfTECTfO
rr ;law son

IIIPIfT

gplp2
~~^' . .T Cl1MTRUl~^
- ~
1
I
1
" 1
1
1
1
1
1
1
"
1
1

' 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
10
r wsoFrnrE
r,~~ ~

i

i
13
Z1 17 18
GTR fREn

, "
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