Hatfield 2050 Description And Operating Instructions

J

RF

COMPONENTS

2050 BALANCED

ATTENUATOR

DESCRIPTION

& OPERATING MANUAL

RF

COMPONENTS

I

1*

?

$

*

Gl

#

|]

J

Hatftald

Instruments

»

n

0-121

dB

I

2050

BALANCED

ATTENUATOR

DESCRIPTION

&

OPERATING

MANUAL

Subject

to

change

without

notice.

Printed

in

the UK

Hatfield

Components,

a

division

of

Wandel

&

Goltermann

Ltd.

11.86

ALK

I

CONTENTS

I

y

Chapter

Page

Contents i

History

ii

1.

Preface

1-]

2.

Specification

2-1

3.

Technical

Description

3-1

4. Operation

4-]

5.

Fault Finding

and

Calibration

5-]

6. Application Notes

.

6-1

7. List of Drawings

7-]

8.

Parts Lists

8-1

HISTORY

Product Manual

for Attenuator

type 2050

I

Dec, 1970 Provisional

Issue

1A

Jan. 1971 Issue 1

Jan, 1975 Issue

2

Nov.

1986

Issue

3

ii

fi

PREFACE

The

2050

attenuator

has

balanced

input

and

output

impedances

of

600

ohms,

and

a

range

of

121

dB in

steps

of

O.ldB

over

the

frequency

range

of

d.c.

to

300kHz

.

The

electrical

and

mechanical

specification

of

this

attenuator

makes

it

suitable

for

use in

audio

and

video

transmission

testing

equipment.

1-1

SPECIFICATION

2.1

General

The

2050

attenuator

is

a bench

type

instrument.

which

may

be adapted for

19In. rack

mounting

if

required

(suffix R to

type No

.

)

2,2

Attenuation

Eange

to

121dB in

steps of

O.ldB

selected

by four

controls

as follows:

to

IdB in 10

steps

of O.ldB

to

lOdb

in 10

steps

of l.OdB

to 50dB in

5

steps

of lOdB

to 60dB

in

1 step

of

60dB

2.3

Frequency

Range

Floating:

d.c.

to 300kHz

Non-floating:

d.c. to 100

kHz

2.4

Input/Output

Impedance

600 ohms

balanced

Better

than 32dB over

the frequency

range

of

d.c.

to

300kHz

when the

output is

terminated

in

600

ohms

H'

2.6

Balance

-60dB

between

d.c. and

300kHz.

2.7

Accuracy

to IdB:

±0.02dB

1 to lOdB:

±0.1dB

10 to

lOOdB:

±0.3dB

2-1

2.8

Insertion

Loss

<0.2dB,

d.c, to

300kHz

2 .

9

Power

Capable

of

continuous

use

at any

attenuator

setting

without

damage

or

loss

of

accuracy

when

driven from a

+25dBm,

600

ohms,

source

correctly

terminated.

2.10 Ambient

Temperature

Operating: to

+40°C

Storage:

-20

to +85°C

I

1

I

2.12

Connections

4mm socket

terminals

2-2

\

TECHNICAL DESCRIPTION

]

The 2050 attenuator consists of

three separate

bridged

'

H'

balanced

networks in tandem, and a

fourth employing a double

'T'

network

for

the 0/60dB section. This section

comprises two

30dB networks to

improve the frequency

response.

The

centre-tap of this

section

Is brought out to

the

lower terminal

of the

output side of the

instrument

so that

It may be

connected to case or

ground

if

required,

(see

Application Notes).

Each section is fully screened from

adjacent

sec-

tions. The component

layout

is

arranged to main-

tain an adequate balance of

capacitance

to

the

case

between

each

section.

The front panel

switches select

appropriate

bridging and shunt resistors

for each

step of

attenuation within that particular

section.

3-1

H

OPERATION

I

4.1

Connections

The

attenuator

is ready for

use as supplied.

The

upper

two

terminals form

the

600 ohms

balanced

input

and

output connections.

The

left-hand

bot-

tom terminal

is earthed to the

case. The

right-

hand

bottom

terminal is

the

cent re- tap

of the

0/60dB

section,

(see

Application

Notes for

recom-

mended

use).

J

4-1

1

5.

FAULT

FINDING AND RECALIBRATION

5.1 Fault Finding

In general, faults

in

attenuators are due to input

levels in excess

of

the rated maximum or

dirty

switch contacts.

If the location of

the fault

does

not become

apparent

following

a

visual

inspection,

then

proceed as

follows,

using a

suitable

oscillator and level

measuring

instru-

ment:

I

With all the controls

set to

'OdB'

,

check that a

'through'

balanced

signal can be

obtained.

This

will indicate that the

input/output wiring and the

'bridging' switches

are in

circuit and functioning

correctly.

Check

each step

of the

four attenuator

sections in

turn, and

each

whole section

against

a

step

of the

following section until the

fault condition is

shown.

If resistors are at fault

they

must be replaced by

the types

specified

in the Parts Lists at

the

rear

of this manual.

5.2 Recalibration

J

If

the

fault

proves to be more

than just a simple

replacement

of

a

resistor or the

cleaning

of

switch contacts,

then

the attenuator should be

checked against a

'standard' unit

and the

tests

called

for in the

manufacturing

specification

carried out.

It is strongly

recommended that

recalibration

be carried out by

the Service Dept.

of Wandel &

Goltennann Ltd. or an

approved organi-

sation

appointed for this

purpose.

5-1

APPLICATION

NOTES

6.1 Use

of

Balanced

Attenuators

A

commonly employed

attenuator

section

for

balanced

systems is the 'H'

section

utilising five

resistors in an H-conf

iguratlon.

Where

a

range

of

attenuation is

required, e.g. I

to lOdB in ldB

steps, different

values

of

centre

resistor are

selected

together with

appropriate

values shunting

the series

'legs'. This

arrangement

is known as a

bridged-H

section and,

besides

being

balanced,

this type of section

is

also

floating,

i.e. not

referenced to

ground.

1

An alternative

arrangement

which may

be used in a

balanced

attenuator

consists of

two bridged-T sec-

tions, one for each leg

of the

balanced circuit.

The

earthy

ends of the

'T' sections

are

connected

together,

and

whether

left floating

or

grounded,

the performance is

identical to

that

of the

bridged-H

section so far as

balanced

signals

are

concerned.

However,

unlike the

bridged-H

section,

the

double

bridged-T

with

centre-tap

grounded,

attenuates

longitudinal signals

(also

known

as

signals

to ground,

push-push

signals or

common

mode

signals) to

the same

degree

as balanced

signals

(i.e.

transverse,

metallic,

push-pull or

differential

signals).

These

factors

become

important

when large

attenuation

levels

are con-

sidered as

follows:

Suppose a

balanced ,

floating

attenuator is

set to

120dB and a

signal

is applied

from an

oscillator

whose output

balance is 60dB.

Since a

balanced,

floating

network

provides little

or

no attenuation

of

longitudinal signals,

the

desired

balanced

6-1

signal

at the

attenuator

output

will

be

60dB lower

than

the

unwanted

longitudinal

component.

Thus,

if

the

input

balance

/common

mode

rejection

of

an

indicating

instrument

connected

to the

attenuator

output

was

50dB,

the

indicated

reading

could

be

anything

between

zero

and

twice

the

correct

figure.

To

obtain

an

accurate

reading

the

sum

of

the

sender

balance

in

dB's

and

the

receiver

balance

in dB's

would

require

to

be

around

160dBj

this

is

a

stringent

requirement

even

at

1kHz,

and

almost

impossible

to

achieve

at

20kHz

or

higher

frequencies.

Therefore,

with

a

floating

network,

balance

considerations

usually

limit

the

usable

attenuation

range.

In

contrast,

with

centre-tap

grounded

networks,

the

sender-end

balance

is

maintained

and

dif-

ficulties

outlined

above

are

avoided,

although

at

the

expense

of

a more

complicated

and

therefore

more

costly

attenuator.

At

an

attenuation

level

below

60dB a

floating

network

is

entirely

satis-

factory,

except

at

the

highest

frequencies;

con-

sequently

the

2050

attenuator

uses

bridged-H

networks

for

this

part

of

the

range.

However,

the

0/60dB

section

uses

a

double

balanced-T

network

with

the

cent

re -tap

being

brought

out

to

the

lower

terminal

of

the

three

output

terminals

to

the

right

of

the

front

panel.

Where

balanced,

floating

operation

is

required

no

connection

should

be

made

to

this

terminal.

Where,

however,

attenuation

in

excess

of

60dB

is

required,

it

is

recommended

that

this

terminal

be

connected

to

the

attenuator

case,

the

case

of the

receiving

instru-

ment

and

to

ground.

Where

possible

the

case

of

the

sender

should

also

be

grounded,

although

mains

frequency

earth

loop

considerations

may

make

this

inadvisable.

6-2

1

I

DRAWINGS

7 .

1

List

of Drawings

Circuit

Diagram

4858-CD00.

003/1

Wiring

Diagram .....

4858-WDOO.

003/1

Assembly

of Switch SI

-

l.OdB .

4858-1001.001/1

Assembly of

Switch

S2

-

lOdB . .

4858-1002.000/1

Assembly of

Switch

S3

-

50dB . .

4858-1003.009/1

Assembly

of Switch S4 0/60dB . . .

4858-1004.008/2

7-1

SI

SECTION

to

IdB, 0.tdB

Steps

S2

SECTION

tolOdB,

1dB

Steps

S3

SECTION

to

50dB, 10dB Steps

i

1r2

1r3

Irs Irs

Ire

\hi

Irb

Ti9

|[,iojfmobf

6R^32R^8R^5Rj?IR5jl7R6|wRlJl0Ri[6fI93j6fi93

6R93I

la

b

1«

U V-

iBi Tr? Tr"3

]ut

Irs

[rb

\m

Jrb

Irs

IrioT (r

6(9R

KbSUSAR

372H299R

233R175R 124R

77R7

3SR9

J9

14 4

m

?

S4

SECTION

0/6

OdB

Steps

S4u

OdB

^<

22

©

•"[

l~

60dB

R3

19R

;60dB

a.

R6 282R

a Sia"

OdB

R7 563R

I

15—

I

1

19rM

11

19rM

i \2L-r

RS

563R

-OCT.

OdB

Sic

Fig.

1

Circuit

Diagram,

2050

Attenuator

®

.ffi.

nfOrcs

ALL

SWITCHES

VIEWED FROM FRONT

WRAP ALL

COHHECTIONS

1

TURKS

ALL WIRES

TO

BE

7/0076

PVC COVERED

WIRES

TO

BE

SLEEVED

WITH IDENTIFICATION

SLEEVES

NUMBERED AS

SHOWN

©

WIRES FROM

WAFER

TO

WAFER TO

GD

DIRECT

AND

HOT LOOPED

OVER

ONE AHOTHER

Cin

CONNECTED AS REO

BETWEEN

EARTH

&

EITHER IHPUT

TERMINAL.

Coirt

COHHECTED

AS REQ'O

BETWEEN EARTH

&

EITHER

OUTPUT

TERM1HAL

.

OUTPUT

FHOHT

0-VOdB

C

out

u

TERW'lAL

CONNECTION

(FRONT

TAG)le

TAG

NEAREST

FRONT PANEL

REAR

TAG EARTHED TO

CHASSIS.

0-10dB

0-50dB

0-60dB

Wiring

Diagram, 2050

Attenuator

I

.

1 FOR

R10(a)&lb)&fl3Mo)ifb)

B

33fl(/.0FF)

SEE FIG. BELOW.

A

1

IN

OUT

RESISTORS ARE

BENT

AS

SHOWN

AND

SOLDERED INTO

EYELETS

ITEM 2.

OUT

Fig. 3 Assembly of Switch SI ,

- l.OdB

IN

OUT

IN OUT

Assembly of Switch S2 ,

-

lOdB

I

Fig. 5

Assembly of

Switch S3,

-

50dB

l.TORRTZabc

5<7Djl

SEE FIG.

BELOW

RESISTORS

ARE BENT AS SHOWN AND SOLDERED

EYELETS HEM 2

=

—

-

DEMOTES

SLEEVED

LEAD

WIRE

IN

REO

TERMINAL

(RED

OUT

Fig. 6

Assembly

of

Switch

S4 ,

0/60dB

!i

J

L

I

8.

PARTS

LISTS

REF.

VALUE TOL.±X

RATING

TYPE

PART NO.

SWITCH

1,

to IdB

Rl

36R6

1

0.25W H4

lOOppm

4980-0000.232/-

R2 32 R7

1

0.25W

114

lOOppm

4980-0000.229/-

R3 28R9

1

0.25W H4 lOOppm

4980-0000.216/-

R4

25RO

1

0.25W H4 lOOppm

4980-0000.203/-

R5 21R5

1

0.25W H4

lOOppm

4980-0000.193/-

R6

17R6

1

0.25W H4 lOOppm

4980-0000.180/-

R7

14R1 1

0.25W

H4 lOOppm

4980-0000.177/-

R8

10R4 1

0.25W

H4

lOOppm

4980-0000.164/-

R9

6R93

1

0.25W H4

lOOppm

4980-0000.151/-

RlOa 6R93

1

0.25W H4

lOOppm

4980-0000.151/-

RlOb

6R93

1

0.25W H4

lOOppm

4980-0000.151/-

Rll

300R

0.1

0.25W H4 lOOppm

4980-0000.397/-

R12

300R

0.1

0.25W

H4 lOOppm

4980-0000.397/-

R13

4k92

1

0.25W H4 lOOppm

4980-0000.423/-

R14 5k50

1

G.25W

H4

lOOppm

4980-0000.436/-

R15

6k22

1

0.25W H4

lOOppm

4980-0000.449/-

R16

7kl5

1

0.25W H4 lOOppm

4980-0000.452/-

R17

8k45

1

0.25W

H4

lOOppm

4980-0000.410/-

R18 10k4

1

0.25W H4

lOOppm

4980-0000.407/-

R19

13k2 1

0.25W H4

lOOppm

4980-0000.533/-

R20 17kl

1

0.25W H4

lOOppm

4980-0000.672/-

R21

25k8

1

0.25W H4

lOOppm

4980-0000.685/-

R22

56

kO

1

0.25W H4 lOOppm

4980-0000.559/-

R23 300R

0.1

0.25W H4

lOOppm

4980-0000.397/-

R24

300R 0.1

0.25W H4

lOOppm

4980-0000.397/-

R25 36R6

1

0.25W H4 lOOppm

4980-0000.232/-

R26

32R7 1

0.25W H4

lOOppm

4980-0000.229/-

R27 28R9

1

0.25W H4

lOOppm

4980-0000.216/-

R28 25R0

1

0.25W H4

lOOppm

4980-0000.203/-

R29

21R5

1

0.25W H4

lOOppm

4980-0000.193/-

8-1

REF.

VALUE

T0L.±X

RATIHG

TYPE

PART

NO.

R30

R31

R32 R33

R34a

R34b

17R6 14R1 10R4

6R93 6R93 6R93

0.25W

SWITCH

2,

to

lOdB

Rl R2

R3

R4

R5 R6 R7

R8

R9

RIO

Rll

R12 R13 R14

R15

R16

R17 R18

R19

R20

R21 R22 R23

R24

8-2

649R

54

5R

454R

372R 299R

233R

175R

124R 77R7

35R8

300R

278R

300R 398R

485R

603R 771R

lk03

lk45

2k32 4k92

300R

1

I

1

0.1

1

1 1

1

0.1

0.25W

H4

lOOppm

H4

lOOppm

H4

lOOppm

H4 lOOppm

lOOppm

H4 H4

Switch

Wafers,

Sla,

b,

c, d

(4)

H4 lOOppm

H4

lOOppm

H4 lOOppm

H4

lOOppm

H4 lOOppm H4 lOOppm

H4

lOOppm

H4

lOOppm

H4

lOOppm

H4 lOOppm

H4 lOOppm H4

lOOppm

H4

lOOppm

H4

lOOppm

H4

lOOppm

H4

lOOppm

H4

lOOppm

H4

lOOppm

H4

lOOppm

H4

lOOppm

H4 lOOppm

H4

lOOppm

H4

lOOppm

4980-0000.180/-

4980-0000.177/-

4980-0000.164/-

4980-0000.151/- 4980-0000.151/- 4980-0000.151/-

4858-0130.009/3

4980 4980

4980

4980 4980

4980

4980-

4980- 4980-

4980- 4980- 4980-

4980-

4980- 4980- 4980-

4980- 4980-

4980- 4980- 4980-

4980-

-0000

-0000. '0000,

-0000.

0000

0000.

0000

0000.

.630/-

.504/- .614/-

.494/-

.601/- .588/-

-575/- .562/- .724/- .711/- ,397/- .397/- ,591/- ,481/-

520/-

517/-

627/-

643/-

656/- 546/-

669/-

423/-

397/-

m m

m

4 J

REF.

VALUE TOL ±X RATING TYPE PART NO.

R25

649R

]L

0.25W H4

lOOppm 4980-0000.627/

R26 545R ]

L

0.25W H4 lOOppm

4980-0000.504/

R27 454R ]

I

0.25W H4 lOOppm

4980-0000.614/

R28 372R ] L 0.25W H4 lOOppm

4980-0000.494/

R29 299R

]

L 0.25H H4 lOOppm

4980-0000.601/

R30 233R

]L

0.25W H4 lOOppm

4980-0000.588/

R31 175R ]L 0.25W H4 lOOppm

4980-0000.575/

R32 124R ]I

0.25W

H4

lOOppm

4980-0000.562/

R33

77R7 ]

1

0.25W H4 lOOppm

4980-0000.724/

R34

35R8 ] I

0.25W H4 lOOppm 4980-0000.711/

Switch Wafers, S2a , b, c, d

(4)

4858-0130.009/3

SWITCH

3,

to 50dB

I

Rl 649R 1

0.25W H4 lOOppm 4980-0000.630/

R2 2k70 1

0.25W

H4

lOOppm 4980-0000.287/

R3 9kl0 1

0.25W

H4 lOOppm

4980-0000.478/

R4 29 k7 1 0.25W H4 lOOppm

4980-0000.698/

R5 94 k6 1

0.25W

H4

lOOppm

4980-0000.915/

R6 300R 0.1 0.25W H4 lOOppm

4980-0000.397/

R7 300R 0.1 0.25W H4 lOOppm

4980-0000.397/

R8 278R 1

0.25W H4

lOOppm

4980-0000.591/

R9 66R7

1 0.25W H4 lOOppm 4980-0000.753/

RIO 19R6

1 0.25W H4 lOOppm

4980-0000.740/

Rll 6R06 1

0.25W H4

lOOppm

4980-0000.737/

R12a

5R70 1 0.25W H4 lOOppm

4980-0000.708/

R12b

5R70 1 0.25W H4 lOOppm

4980-0000.708/

R12c

5R70 1 0.25W

114

lOOppm

4980-0000.708/

R13 300R

0.1 0.25W H4 lOOppm

4980-0000.397/

R14 300R 0.1 0.25W H4 lOOppm

4980-0000.397/

R15

649R 1 0.25W H4 lOOppm

4980-0000.630/

R16 2k70

1 0.25W H4 lOOppm

4980-0000.287/

R17 9klO 1 0.25W H4 lOOppm

4980-0000.478/

R18 29 k7 1 0.25W H4 lOOppm

4980-0000.698/

8-3

REF.

VALUE

TOL.±Z

RATING

TYPE

PART

NO.

R19

94k6

1

0.25W

HA lOOppm

4980-0000.915/-

Switch

Wafers,

S3a, b,

c

(3) 4858-0130.009/3

SWITCH

4, 0/60dB

Rl

282R

L

0.25W

H4

lOOppm

4980-0000.928/-

R2

282R

L

0.25W H4

lOOppm

4980-0000.928/-

R3

19R0

I

0.25W

H4

lOOppm

4980-0000.944/-

R4

19R0

L

0.25W

H4

lOOppm

4980-0000.944/-

R5

563R

]

L 0.25W

H4 lOOppm

4980-0000.931/-

R6

282R ]

I

0.25W

H4 lOOppm

4980-0000.928/-

R7

563R

]L

0.25W H4

lOOppm

4980-0000.931/-

R8

19R0 1

0.25W

H4 lOOppm

4980-0000.944/-

R9

19R0 1

0.25W

H4

lOOppm

4980-0000.944/-

RIO

282R ]

0.25W

H4 lOOppm

4980-OOO0.928/-

I

Switch

Wafers,

S4 a,

b , c

4858-0132.007/3

V

8-4

I

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&

Manufacturing

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Eurotech

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Burrington

Way, Progress

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Plymouth,

Devon.

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41

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Tel: 0752

772773

Greenford,

Middlesex. UB6 9AH

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Tel:

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3020

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45592

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