BRUEL & KJAER 1022 - Oscillator and Mixer Section

BRUEL & KJAER 1022

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Description

of

the

Oscillator·

and

Mixer-Section.

Fig. 1.1

shows

a

block

diagram

of

the

complete

Oscillator

.

The

fixed

oscillator

is

tufied

to

120 k

c/s

and

can

be

frequency

modulaled

.

The

reactance

tube

circuit

acts

as

a

variable

inductance

and

the

modulation

swing

can

be

varied

from

0

to

± 250

c

/

~y

means

of

a

switch

on

the

front

panel

of

the

apparatus,

marked

FREQUENCY

DEVIATION.

By

means

of

the

switch

marked

MODULATION

FREQUENCY

the

frequency

of

the

built

-

in

saw-tooth

oscillator

may

be

chosen.

Frequencies

of

1-

1.6--2.5

-4-6.

3-

10-16

and

25 c/s

are

available.

The

oscillator

is a

blocking

type,

tuned

to

approximately

7 Mc/s,

and

Lhe

frequency

of

the

saw-tooth

oscilla-

tions

is

set

by

changing

the

grid

resistor.

Fixed Variable

)J

Oscillator

Amplifier

Regulating

Amplifier

Mixer

Low Pass

Filter

Variable

Oscillator

I

I

I

I

I

I

I

I

I

I

I

Impedance

Output

Matching

Amplifier

Circuit

Ref. Sig. Remote

1000c

;

~l

~

Fontrol

I

Magnetic

:

Clutch

1

I

Output

Attenuator

Load

Output

Attenuator

Output

Fig. 1.1.

Block

Diagram

of

the

Beat

Frequency

Oscillator 1022.

Provision

is

made

for

external

modulation.

The

external

generator

should

then

be

connected

to

two

terminals

of

the

socket

on

the

front

plate

marked

REMOTE

CONTROL.

For

external

modulation

a

voltage

of

approximately

3.5

volts

is

necessary

when

a

modulation

swing

of

± 250

c/s

is

required.

When

external

modulation

is

etmployed

the

switch

marked

MODULATION

FREQUENCY

must

be

in

position

"Ext.

Mod.",

as

in

this

position

of

the

sw

itch

the

reactance

tube

is

on

and

the

saw-tooth

oscillator

is

off.

A

variable

capacitor

inserted

in

the

tuned

circuit

of

the

fixed

oscillator,

arid

operated

by

the

knob

marked

FREQUENCY

INCREMENT,

permits

exact

frequency

selection

in

the

range

.± 50 cis

for

any

setting

on

the

main

scale.

Thus,

using

this

capacitor,

frequencies

down

to

zero

may

be

obtained

,

even

t!J.ough

the

main

scale

is

only

calibrated

from

20

c/s

to

20ooo

cis:

By

means

of

a

noiseless

switch

on

the

front

panel,

marked

OSCILLATOR

STOP,

the

voltage

on

the

anode

of

the

120

kc

/s

oscillator

can

be

disconnected.

6