Mcmartin B-910 User manual

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

~

f=

\W

....- -

--~

---:;

(7···

..

1

INSTRUCTION MANUAL

8-9101·

10

watt

FM

Exciter/Transmitter

TECHNICAL

SPECI

FICATIONS

..

II

INTRODUCTION

...........

2

III INSTALLATION

AND

UNPACKING

..............

3

IV GENERAL CIRCUIT

DESCRIPTIONS

..

. . . . . .

....

4

V

OPERATION

.

...

.

..

. .

.....

11

VI

CALIBRATION

PROCEDURES'

..

12

VII

STANDARD

PRE-EMPHASIS

CURVE. . . . . . . . . . . . . . .

..

16

VIII

FCC

STANDARDS

...........

17

IX

PARTS

LIST

..............

17

X

SCHEMATIC

DIAGRAMS

.......

23

The

8·910

and B-910T

are

type

accepted

for

use

under

part 73 of

the

FCC

Rules

and Regulations

for

monaural

operation, and with

the

addition

of

the

8-110

and/or

B-1l3

Stereo/SCAassemblies,

this

equipment is further

type

accepted

for

stereophonic

and/or

SCA

operation.

[8SD~(Q)I·

I.

TECHNICAL SP

ECIFICATIONS

OPERAT

I

NG

RANGE:

....

Specified frequency in

88

to

lOa

MHz

ronge.

RF

OUTPUT

6·

910

E

x ci

te

~

:

2·1

5W co

nt

inuousl y ad·

POWER:

.

..•.

......

..

. .iuslo

bl

e. 6·

910

T

10

wa

tt

rrans

mi

ller:

10 watts n

om

i

na

l.

RF

OUTPUT

IMPEDANCE:

...

•

.....

.

......

. . . .

..

...

..

.

......

. .

..

50

ohms

CENTER

FREQUENCY

STABILITY:

..

...

..

...

..

.

.......

..

.

..

. .

..

.

..

. .

..

.. :t 500

Hz

MODULATION

CAPABILITY: .

...

. .

..

.

.............

.

..

.......

. !

150

kHz

AUDIO

INPUT

IMPEDANCE:

.

.....

. . •

....

. . .

...

.

.•..

.

..

.

..

600

ohms

,

ba

lanced

AUDIO

INPUT

t

10

! 2

dBm

LEVEL: ..

..

.

..

. .

..

•

..

....

..

...

.

...

,

AUDIO

FREQUENCY

RESPONSE:

..

. .

.. ..

.

....

:!:

0.5

db

30

Hz -

15

kHz

(7

5 usee pre·

emphasi s)

TOTAL

AF

HARMONIC

DISTORTION:

.

..

.

..

•

...

. . . . . .

...

..

. .

..

0.3%,

30

Hz

-

15

kHz

FM

NOISE:

..

....

..

...

....

.

..

. .

68

dB

be

lo

w

100"

;';

m

odu

lati

on

AM

NOISE

:

...

.

....

. .

..

........

.

...

....

65

dB

be

low carrier

lev

el

POWER

REQUIRED:

.•

.•.....

. . . 115

VA

C

or

230 V

AC,

:!:

1

5%,

50

_

60

Hz

50 wo

tts

OPERATING

TEMPERATURE

:.

..

.

....

.

....

.

....

..

. . . . -

20

1>

to +

50

0

Ce

lsius

MECHANICAL

:

8.

910

Exciter

...

. .

.......

. .

(W

) 19"

(E

IA

Std

.

Rock

"'-'unl)

(H)

lO

t "

(0)

17

:"

8.910T Transmitter

..

.....

.

.....

.

..

......

..

....

. (W) 20"

(H

) l

W'

(0)

18"

WEIGHT:

.

..........

_

..

. .

..

_

.......

..

...

..

...

-

25

Ibs

. (6·910)

30

lb

•. (B·

910T

}

FINISH:

..

.

....

..

....

..

.

McMo

rtin be

ig

e w

ith

w

oodgr

ai

n t

ri

m

fron

t

access

ponel

STEREO

EMISSION:

...

.

..

. .

_.

_

........

.

...

............

...

. . 3

00

F9

AUDIO

I

NP

UT

IMP

ED

ANCE:

......

. . . . • . . .•• Lo

ft

Channol

600

ohm

~

,

ba

lanced

RighI

Channel

600

ohms

,

bal

anced

A

UDIO

I

NP

UT +

10

± 2

dBm

LE

VEL:

..

. .

..

...

..

. . . . . .. .. . . .

..

.

..

.

••.

•. ,

1/74

AUDIO

FREQU

E

NCY

RESPONSE:

. . .

......

.. . ± 0.5

dB,

30

-15,000

Hz

Loft

or

Right

Channel

DISTORTION:

...

.. .

..

.....

.

...•.•.

0.5%

or

Ius,

30

-15,000

Hz

STEREO

SEPARATION: . .

.•

..

. . 39

dB

or

greater, module only

35

dB

through exciter

(50

-15000

Hz)

FM

NOISE:

. . .

....

..

.

..

. . Greater than

65

dB

below

100%

modulo

-

ti

on

PILOT

STABILITY

RANGE:

..

. . . . . •.

....

•

...•

! 1

Hz

ov

er rated temperature range

SUBCARRIER

SUPP

RES

SION

:

...

..

...

......

...

..

.

..

.

..

. . 55dB

or

greater

47

dB

or

greater, less

15

kHz LP Ii

It

ers;

CR

OS

ST

A

LK:

.

....

..

....

50

dB

(30

·

50

00

Hz)

; 45

dB

(5

·

10

kHz);

4

0dB

(10

-1

5 kHz) with

fi

lters.

S

CA

A

UDIO

INPU

T . .

..

+

10

, ± 2

dBm

LEVEL: .

..

. .

...

. .

•...

•

...

.

•....•

.

.. ..

.

..

. . .

IN

PU

T

IMPE

D

ANCE:

..

...

..

....

. . . . . . . . . .

...

.

..

.

..

.

...

. . . . .

600

ohms

SCA

CARRIER

FREQUENCY

:

....

.

.....

41

kHz

Or

67

kHz

standard (other

fre-

quencies "re avoilable

On

special order)

SCA

CARRIER

S

TA

BI

L

ITY:

.

..

.

.................

.

....

..

......

±

500

Hz

M

ODU

LAT

I

ON

CA

PAB

ILIT

Y:

..

.

........

....

. .

..........

1:

7.5

kHz

(1

00

%)

PRE·

EMP

HA

SIS:

. . . .

..

.

..

15

0

mic

roseconds, standard; 50

or

75

usec avai lable

on

request

FREQ

U

ENC

Y

RESP

O

HSE

:

..

.

..........

..

. .

....

..

.

...

.±

1.5

dB

,

SO

-

SOO

O

Hz

CROSSTAL

K -

MA

IN

TO

SUBCHANNEL

...

.

..

.

60

dB

Or

greater below

program

levels

C

ROSSTALK

-

SUBCHANNEL

INTO

MAIH

...

.

...

.

..

60

dB

Or

greater belaw

program

level

DISTORTION:

.......

. 0.75% or less,

50

-5,000

Hz

LP

lilter

2.5%

or

less,

50

-5,000

Hz

BP

Ii

Iler

FM

NOIS

E:

...

.

...

....

60

dB

be

lo

w

10

0%

mo

dulati

on

rt 6kHz

deviation) 1

50

usee

de-

em

pha

sis

AUT

OMA

T

IC

MUTE

: .. .

REMOTE

CONTR

OL:

..

Adi

USloble to a

ny

level between

100%

modu

lati

on

an

d

3%

modu

lation, with

varia

bl

e

mu

te delay

seA

su

bcarrier

mo

y

be

held

on

by a

Iro

nt p

an

el

swi

tch

or

by

a

re

mot

e can·

tral closure

.,-

~

II.

INTRODUCTION

The

McMartin

8-910

modular

FM

exciter

and

8-910T

10

watt

FM

broadcast

transmitter

designs

incorporate

the

most

recent

direct

FM

sol

id

state

technology.

The

modular

design

allows

complete

flexibility

in

operat-

ing

modes.

All

possible

comb~nations

of

monaural,

stereo,

and

SCA

operating

modes

presently

authorized

by

the

Federal

Communications

Commission

may be

accommodated

by

use

of

optional

plug-in

modules.

Electrical

parameters

conservatively

meet

or

exceed

the

requirements

of

Part

73

of

the

Commission

Rules

and

Regulations.

A

list

of

minimum

broadcast

stand-

ards

will

be

found

in

the

rear

of

this

manual

for

the

purpose

of

aiding

the

broadcaster

in

checking

the

per-

formance

of

the

8-910

equipment.

A

tabulation

of

actual

performance

measurements

for

the

equipment

received

is

shipped

with

the

unit.

This

table

will

serve

as

a

reference

far

operating

parameters

in

the

event

trouble

occurs.

The

8-910T

consists

of

a

8-910

exciter,

plus

a

low-

pass

output

filter

and

cabinet.

Mon

aural

Operation

The

standard

8-910

unit

is

equipped

with

modules

for

monaural

operation.

(See

Figure

1--Plug-in

module

locator

diagram.)

The

8-910

exciter

main

frame

is

pre-

wired

for

later

conversion

to

stereo

or

stereo/SCA

operation

by

insertion

of

appropriate

modules.

This

includes

six

of

the

nine

possible

modules

as

standard

equipment.

seA

Operation

When

operating

in

the

monaural

mode,

two

optional

SCA

channels

are

available.

The

standard

SCA

sub-

carrier

frequencies

available

are

41

kHz

and

67

kHz.

Modules

for

other

subcarrier

frequencies

are

avai

lable

on

special

order.

The

individual

SCA

generators

may

be

turned

on

or

off

remotely

through

rear

chassis

ter-

minals.

150

microsecond

preemphasis

is

standard.

50

or

75

microsecond

preemphasis

is

available

on re-

quest.

Stereo

Operation

Stereo

operation

employs

a

plug-in

Stereo

Generator

Module

in

Position

Oc

2 and a

Dual

Audio

Module

in

place

of

the

single

module

used

in

the

monaural

ver-

sion

in

Position

.:0

1.

The

dual

audio

module

is

used

to

process

the

left

and

right

channel

audio

signals

for

modulation.

When

operating

in

the

stereo

mode,

an

additional

67

kHz

sub

channel

option

may be

accom-

modated.

The

41

kHz

sub

channel

is

not

available

whi

Ie

operating

stereo

since

thi

s

part

of

the

composite

spectrum

is

used

by

the

L-R

stereo

information.

The

19

kHz

pilot

subcarrier

is

controlled

by a

switch

pro-

vided

on

the

front

of

the

stereo

generator

module

or by

a

simple

contact

closure

on

the

rear

of

the

exciter

for

remote

control

operation.

See

Fig.

3,

System

810ck

Functional

Diagram.

Alarm/Control

Circuitry

Automatic

off-frequency

detection

is

accomplished

In

two

ways.

First,

by

sampling

the

AC

component

of

the

high

frequency

phase

comparator,

and

secondly,

com-

paring

the

output

frequency

to

a

crystal

controlled

frequency

detector

and

utilizing

the

resulting

IF

sig-

nal.

For

deviations

in

excess

of

100

kHz,

the

absence

of

an

IF

signal

removes the

DC

collector

supply

volt-

age

from

the

power

amplifier

module.

o

~

D

0 !

5

~

...

'"

0 0 ...J

I-

0

"2':

«

I-

0

0 ...J «

'"

C>:

0

...J

IJJ

I-

0

~

u Z

"2':

I-

0

IJJ

0 «

~

..,

u "-

...J

0 0 w

'"

::>

0 w U

..

<:

<.:>

I-

z w

::>

« w 1

'"

C « ...J

'"

w

""

~

...J

::>

III

.~

3'

w

~

« 0

OJ..

-I

0

~

;;.

::>

0 w 0

~

o

'"

""

"'- "'-

MODULE

NOS

' 1

~

2

"3 "4 ' S ' 6 -7

;;1l

FIG

1 FRONT

VIEW

PLUG

IN

MODULE

LOCATOR

DIAGRAM

-2-

11/73

III, INSTALLATION

AND

UNPACKING

After

unpacking

the

FM

exciter,

a thorough

inspection

should

be

conducted

to

reveal

any

shipping

damage.

If

any

damage

is

noticed,

immediately

notify

the

ship-

ping

agency

and advi

se

McMartin

Industries,

Inc. of

said

action.

Check

to

see

that

all

modules

are

secure-

ly

positioned

in

their

respective

locations.

Figure

1,

the

Plug-in

Module

Locator

Diagram,

should

be

used

for thi s

purpose.

Module Complement

Stereo

.1

Dual Audio

'

.2

Stereo

Generator

113

SCA

11

1(if

used)

~

Modulated Osci Ilator

Monaural

Mono

Audio

SCA

*2

(If

used)

SCA

.1

(If

used)

Modulated

Osci

lIator

.5

Reference

Generator

Reference

Generator

;t6 Alarm

and

Control Alarm

and

Control

. 7 RF Power Amplifier RF

Power

Amplifier

118

Power

Supply

Regulator

PowerSupply

Regulator

In

addition

to

the

above

items

each

B-

910

FM

Exciter

includes

a module

extender

card

(P

I N

555009)

for

test

and

repair

purposes

.

McMartin

Industries

recommends

that

installation

per-

sonnel

completely

fam i

liarize

themselves

with

the

ex

-

citer

before

proceeding

with

installation.

Early

plan-

ning

based

on

good

engineering

practices

will con-

tribute

to

stable

and

reliable

operation

of

the

B-910

exciter

.

Mechanical

The

modular

approach

used

in

the

B-910

provides

easy

removal of

practically

all

components

for

service

or

routine

i

nspection

and

maintenance.

Each

module is

easily

removed

by

exerting

a forward pull on

the

han-

dle

provided.

Access

to

the

rear

of

the

cabinet

is

by

removal

of

the

screws

securing

the

rear

panel.

The

top

cover

is removable for

access

to

the

meter

switch

and

meter

amplifier

.

STEREO OPTI

ON

r

--

-

-----------,

)

,~

DUAL

I'

I AUDI O I

IDEL

ET

E L

R'

,

SeA

21 STERE 0 II

Ir

--

GENERATOR I J

4

------------:..J

I

I MONAURAL

AU

DI0

SCA

# 1

OPTIONAL

SCA

oJ

2

OPTIONAL

[850®lJ@1·

All

wiring

to

the

B-910

should

be

installed

in

conduit

using

shielded

wire

to

prevent

RF

pick

up.

Power

Requirements

The

power

transformer

located

an

the

top

rear

of

the

exciter

may

be

operated

from

either

115 or 230 YAC

single-phase

sources.

Factory

wiring

is

for 110Y

oper-

ation.

For

230Y

operation,

refer to

Figure

2

below

for

proper

transformer

primary

connection.

Replace

the

front

panel

fuse

with

a

1I2A

slo-blo

fuse.

BlK

A.C.

IN

BlK

I RED I

WHT

BlK

/

WHT

___

--'

FIG

. 2

ERED

RED I

YEl

35V

1.6A

RED

E

BRN

/

WHT

l2VCT

IA

BRN

E

BlU

I

WHT

lOY

CT

IA

BlU

Power

Transformer

Connections

The

B-910

wi

II

operate

satisfactorily

with a

line

voltage

of 117 YAC, ±

15%

AC .

Power

connection

is

made

to

TB-1

terminals

1

and

2. Terminal 3 is

chas

-

sis

ground.

Input-Output

Connections

lB·l

1

2

3

4

5

6)

7)

Phase Lock

Indi

cator

8)

115VAC

115

VAC

Chassis

Ground

(Normally Closed

(Norma

lIy

Open

(Pole

":"

FIG,

3

SIMPLIFIED

BLOCK

FUNCTIONAL

DIAGRAM

11/73

-3-

lB

-2

1

2

3

4

5

6

7

8

lB-3

1

2

3

4

5

6

7

8

RF

power

amp

DC

voltage

interrupt

RF

power

amp

DC

voltage

interrupt

SCA

~

1

Audio

Input

SCA n 1

Audio

Input

SCA

1/

2

Audio

Input

SCA

~

2

Audio

Input

Connect

to

ground

for

stereo

operation

Ground

Monaural

audio

input

-

red

Monaural

audio

i'

nput

-

black

SCA

1/

1

Remote

Contro

I

(+)

SCA

1/

1

Remote

Control

(Ground)

Stereo

left

audio

input

-

red

Stereo

left

audio

input

-

black

Stereo

right

audio

input

-

red

Stereo

right

audio

input

-

black

Stereo

Generator

Assembly

Exciters

which

include

the

B-ll0

Stereo

Generator

Assembly

as

part

of

an

original

order

are

ready

for

stereophonic

operation

when

received.

If

the

Stereo

Generator

Assembly

is

ordered

at

a

later

date,

the

assembly

will

consist

of a

B-lll

Dual

Audio

Modu I

e,

a

B-

112

Stereo

Generator

ModuIe

and

a

Band

Pass

Filter.

See

Figure

1 for

the

proper

module

loca-

tion

of

the

B-lll

and

B-112

modules.

To

install

the

Band

Pass

Filter,

remove

the

rear

cover

of

the

B-910.

Remove

the

sma

II

pi

ate

located

on

the

top

of

the

unit,

by

removing

the

four

machine

screws

holding

it

in

place.

Directly

below

the

plate

location

are

Cables

No. 34 and

35

.

Solder

the

black

leads

of

these

two

cables

to

the

"GND"

terminal

of

the

fi

Iter.

Connect

the

red

lead

of

cable

34 to

the

"OUT"

termi-

nal,

and

the

red

lead

of

cable

35

to

the

"IN"

terminal

of

the

fi

Iter.

Secure

the

fi

Iter

to

the

top

of

the

exciter

and

replace

the

rear

cover

of

the

unit.

The

exciter

is

now

equipped

for

stereophonic

operation.

IV.

GENERAL

CIRCUIT

DESCRIPTION

The

B-910

exciter

system

uses

a

free-running

direct

FM

osci

Ilator

operating

at

one-half

the

specified

out-

put

frequency.

The

center

frequency

of

the

osci

Ilator

is

precisely

maintained

by

phaselock

techniques.

The

~

>-

IN

t=

Q1

EMITTER

FOLLOWER

I

,II

f

·1

~

oscillator

frequency

is

doubled

and

ampilfied

to

ap-

proximately

0.25-watt

level.

This

operating

frequency

signal

is

sampled

and

divided

by

10,000

to

produce

a

frequency

in

the

8.8

to

10.8

ki

10Hertz

range

(one

ten-

thousandths

of

the

specified

operating

frequency

in

the

88

to

108

MHz

FM

broadcast

spectrum).

This

divider

output

frequency

is

compared

with

a

frequency

in

the

8.8

to

10.8

kHz

range

generated

by

dividing

by

1000

the

output

frequency

of

a

temperature-controlled

refer-

ence

crysta

I

osc

i

Ilator

dperati

ng in

the

8.8

to

10

.8

MHz

(one-tenth

the

operating

frequency)

range.

The

two

frequencies

in

the

8.8

to

10.8

KHz

range,

one

derived

from

the

modulated

oscillator,

the

other

from

the

reference

oscillator,

are

fed to a

phase

comparator

and

phase-to-voltage

converter.

The

DC

output

of

the

converter

provides

a

correction

voltage

to

voltage-

variable-capacitor

circuitry

in

the

frequency

determin-

ing

tank

circuit

of

the

modulated

oscillator.

This

"locks"

the

oscillator

frequency

precisely

to

one-

half

the

output

frequency

.

The

phaselock

loop

wi

II

respond

only

to

submultiples

of

the

operating

and

reference

frequencies

appearing

at

the

phase

comparator

inputs.

If

malfunctions

occur

in

the

divider

circuitry,

the

control

voltage

will

dis-

appear

and

the

moduI

ated

osc

ill

ator

wi

II

revert

to

a

"free-running"

condition.

When

this

occurs,

automatic

sensing

~ircuitry

in

the

B-910

may be

used

to

trigger

an

external

aural

alarm,

indicating

loss

of

phaselock.

The

exC

iter

center

frequency

can

be

manua

Ily

con-

trolled

pending

circuit

repair.

To

further

insure

aga

in

st

operati

ng

beyond

the

center

frequency

deviation

limits

established

by

the

FCC,the

B-910

incorporates

an

additional

channel

loss

alarm

circuit.

The

B-910

is

automatically

disabled

by

inter-

ruption

of PA

collector

voltage

if

the

unit

is

operated

at

a

frequency

more

than

100 ki

loHertz

removed

from

the

center

frequency.

The

RF

signal

is

ampli

fied

to a

nominal

10-watt

out-

put

level

into

a

50-ohm

unbalanced

load.

Module

Circuit

Descriptions

Electrical

components

in

each

module

are

accessible

by

removal

of

the

individual

module

cover

plates.

Ele-

EMITTER

15kHz

Q2

H

FOLLOWER

~~

AMPLIFIER

AND

EMITTER

FOLLOWER

~OUT

FIG

. 4

BLOCK

FUNCTIONAL

DIAGRAM

MONAURAL

AUDIO

-4-

11/73

ctrical

components

should

be

replaced

only

with com-

ponents

of

equal

value

and

ratings

.

Polarity

of

tanta-

lum

and

electrolyti

c

capac

itors

mu

st

be

ma

inta

ined.

Audio Module (Monaural)

The

audio

module

serves

two

functions.

It

provides

proper

pre-emphasis

of

the

audio

input

signal

and

am-

plifies

the

incoming

signal

level

to

properly

match

the

modulator

audio

input

requirement.

Refer to

Figure

4

and

the

monaural

audio

schematic

diagram (Drawing

11552072/1)

at

the

rear

of

the

manual.

The

incoming

audio

signal

from

TB-3,

1

and

2 (ap-

proximately

+

10dBm,

± 2 dB

at

400

Hz) is fed

to

the

input

line

transformer

located

on

the

monaural

audio

card.

The

transformer

provides

excellent

freq

uency

response

and

converts

the

balanced

configuration

to

unbalanced

input.

A

resistive

pad

(Rl,

2,

and

3) par-

tially

by-passed

with

a high

frequency

compensating

capacitor,

C1, is

driven

by

the

transformer

secondary.

Signal

then

flows

through

Q-l,

an

emitter

follower

used

as

a low

source

impedance

to

feed

the

pre-emphas

is

network

consisting

of

three

precision

resistors,

(R7,

8,

and

9)

and

one

capacitor,

C6.

The

pre-emphasis

capacitor

can

be

switched

in

or

out

by

the

switch

SW-1

mounted

on

the

front

of

the

module.

This

capacitor

is

normally

switched

in.

However,

for

certain

tests,

it

is

more

convenient

to

remove

the

pre-emphasis

network.

The

output

of

the

pre-emphasis

R-C

network

drives

another

emitter

follower

stage.

This

provides

isola-

tion

between

the

network

and a 15 kHz low

pass

filter.

Thefilter

is

followed

by

a low

noise

ampli'fier/

follower

"Combination,

Q-3,

Q-

4.

The

signal

level

from

Q-4,

the

last

emitter

follower,

is

substantially

higher

than

that

required

to

drive

the

modulated

oscillator.

The

signal

is

attenua

·

ted

at

the

modulated

oscillator

cord to mini-

mize

RF

and

noise

interference.

If

it

should

become

necessary

to

alter

the

pre-emphasis

curve,

changing

the

value

of

the

switched

pre-emphasis

capacitor,

C-6,

50MHI

---1~

OSC

'''"'

1

SCA

COMPOSITE

AFC

IN

PUT

""l

FREQ.

VERNIER

1

MH.

OUT

(8)o®lJ(Q)I·

will

alter

the

response

characteristics.

CAUTION:

Do

not

attempt

to

alter

or

adjust

the

15

kHz

low

pass

filter,

FL-1.

The

inductors

are

epoxy

sealed

and

re-

quire

no

adjustment.

Module

Circuit

Descriptions,

Audio

Module

(Monaural)

Verification

of proper

operation

of

this

module

is

ac-

complished

by

connecting

a

600

ohm

balanced

audio

source

of

400

Hz

to

the

line

input

terminals.

Observing

the

wave

form of

the

output

signal,

the

voltage

meas-

ured

at

the

output

terminals

of

the

audio

module

shoulc

be

5

to

7V rms for a +10 dBm input.

Dual

Audio

Module (Drawing

11

559047/1)

The

dual

audio

card

combines

the

circuitry

of

two

mon-

aural

audio

cards

on

one

plug-in module.

Performance

of

both

sections

is

identical.

The

input

attenuator

of

the

right

channel

is

composed

of

two

variable

resis-

tors,

R-20

and

R-21 to

balance

the

gain

of

the

left

and

right

channel

amplifiers.

Each

amplifier

uti

lizes

a

high

frequency

variable

peaking

capacitor

to

compensate

for

slight

differences

in

high

frequency

gain.

Proper

ad-

justment

of

these

components

is

covered

in

the

cali-

bration

section

of

the

manual.

Modulated

Oscillator

Module

(Drawing

11:554021/1)

See

Figure

5,

Block

Functional

Diagram

and

schematic

diagram,

(Drawing

11554021

/

1).

The

modulated

oscil

-

lator

module

is

the

heart

of

the

FM

exciter.

A

simple

LC

osc

i

Ilator,

Q.-

1,

operates

at

exactly

one-ha

If

the

output

frequency.

The

oscillator

is

loosely

coupled

to a

doubler

stage,

Q-2,

which

multiplies

the

oscillator

frequency

.

The

output

frequency

voltage

is

then

amplified

by

three

stages

of

RF

amplification,

Q-3,

Q-4

and

Q-5,

to ap-

proximately

a 0.25

watt

level.

The

RF

amplifier

stages

are

ti

ghtly

coupled

to provi

de

adequate

broadband

char-

acteristics

to

accommodate

all

of

the

FM

sidebands.

The

low

impedance

RF

output

of

the

modulated

osci

1-

lator

is

fed to a push-on

coaxial

connector,

J-1,

on

the

100MHz

RF

OUT

E

","H'

AMP AMP

1 JI ·

'V

rv

~

ru'

LEVEL

10

MH,

1

OOMH

z

TRANSLATOR

+ 10

0-5

V O- (+S V)

0-(

-

5V

) *

ruu

1.r

ru

1

FIG

. 5

BLOCK

FUNCTIONAL

DIAGRAM

MODULATED

OSCILLATOR

11

/

73

-5-

rear

of

the

module.

When

inserting

and

removing

the

modulated

oscillator

module,

make

certain

that

J-1

mates

with

its

chassi

s-mounted

connector

to

prevent

damage

.

The

RF

output

from

the

Q-5

ampl

ifier

stage

also

feeds,

through

C38,

a

frequency

divider

chain,

consisting

of IC-1,

Q-6

and

1C-2.

This

circuitry

drives

the

phase

comparator

sections

of

the

reference

gen

-

erator

module.

IC-1

is

a

divide

by 10,

high

frequency

integrated

circuit.

Q-6

is

a

level

tran~;;lator

to

adapt

the

high

frequency

integrated

c i

rcu

it

output

frequency

(one-tenth

of

the

operati

ng

frequency)

to

a

sta

ndard

low-speed

TTL

divide-by-10,

device

lC

-2.

The

output

frequency

(

880

kHz -

1079

kHz

range)

of

1C-2 is

pre-

ci

se

Iy 1/ 1

OOth

of

the

operati

ng

frequency

and

is fed

to

the

phase

comparator

circuitry

on

the

reference

gen-

erator

modu Ie.

The

50

MHz

LCoscillator,

Q-1,

has

two

DC

inputs

and

two

composite

inputs.

One

of

the

DC

inputs

is

applied

to

both

sides

of

the

frequency

control,

voltage-variable

capacitor-diode,

VVC1

,and

is

the

voltage

derived

from

the

50

MHz

osci

Ilator

frequency

adjust

pot,

R-30

.

This

control

is

used

to

set

the

free-running

freq

uency

with-

in

the

phase

lock

range.

The

other

DC i

nput

to

the

cath-

ode

side

of

the

VVC

1

diode

is

the

ampIi

fi

ed

output

of

the

phase

comparator,

from

the

reference

generator

mod-·

ule.

The

AC

inputs

consist

of

the

monaural

or

stereo

composite

input

and

the

SCA

input

.

These

modulating

signals

are

fed

to

a

pair

of

back-to-back

varicap

mod-

ulators

VVC2

and

VVC3.

Two

VVC's

are

used

as

the

modu I

ator

to

i

ncrea

se

the

Ii

near

range

of

the

vo

Itage-

capacitors

transfer

curve,

thus

lowering

the

harmonic

distortion

.

The

modulation

varicaps

have

a DC

bias

ap-

plied

through

two 82K ohm

voltage

di

vi

ding

res

i

stors,

R 3

and

R 7,

to

select

the

most

linear

portion

of

the

operat

ing

range.

Each

contro

I

and

modu

lati

on i

nput

to

the

modu

la

ted

o

scillator

incorporates

either

RC

or

RLC

filtering

to

prevent

stray

signals

from

modulating

the

oscillator.

The

filters

also

prevent

oscillator

voltage

from

feed-

ing

bock

into

the

external

wiring.

VVCI is AC

coupled

OUTPUT

TO

ALARM

&

CONTROL

l

OOk

l

1'

W

to

the

oscillator

through

C9.

This

allows

the

external

DC

voltages

to

vary

without

affecting

the

quiescent

condition

of Q-l.

Increasing

the

anode

voltage

with

respect

to

cathode

of

the

diode

increases

the

capacit-

ance

.

This

change

in

capacitance

is

minimized

by

the

series

reactance

of

the

5 pf

capacitor,

C9,

coupling

VVCI

to

the

collector

of

Q-1

.

The

resultant

increase

in

capacitance

wi

II

lower

the

frequency.

The

action

of

the

modulation

varicaps

is

simi

lar

to

the

control

vari-

cap;

however

the

composite

or

AC

signal

applied

to

the

modulator

results

in

only

instantaneous

shift

in

frequency

.

The

modulating

frequency

response

of

the

modulated

oscillator

and

varicap

is

limited

only

by

the

shunt

capacitance

of

the

varicaps,which

is

very

low.

The

response

extends

into

the

megaHertz

ronge.

Reference

Generator

Module

See

Figure

6

and

schematic

diagram

(Drawing

11

553031-

/

1).

In

addition

to a

temperature-controlled

reference

crystal

oscillator

and

its

associated

divider

~ircuitry,

this

module

contains:

a)two

phase

comparators,

one

for

the

operating

freq

uency

phaselock

circuit

ry,

and

a

second

for

the

phaselock

loss

alarm

circuits;

b) a

phase-to-voltage

converter

and

additional

dividers

for

the

carri

er

frequency

-der

ived

cha

in.

The

reference

osc

i

Ilator

operates

at

one-tenth

the

spec-

ified

exciter

output

frequency

.

Assuming

a

specified

carrier

frequency

of 99.1 MHz,

the

reference

osci

Ilator

crystal

frequency

would

be

9.91 MHz. Q-1

operates

as

a

conventional

osc

i

llator

whose

frequency

is

crystal

controlled,

stabi

I

ized

in

a 75

degree

Centigrade

oven

located

on

the

front

of

the

module

.

Fine

adjustment

of

the

crystal

freq

uency

is

made

be

adjusting

a

front

panel

control,

R37

which

varies

a DC

voltage

applied

to a

voltage-variable-capacitor,

VVCI .

This

control

is

uti-

lized

for

periodic

correction

of

operating

frequency

as

measured

by

an

ex

ternal

monitoring

service.

Oven

status

is

shown

by

two

front

panel

light-emitting

diode

(LED)

indicator

lamps.

The

output

of

Q-1

is

amplified

and

buffered

by

Q-2.

lOOk Hz

PHASE

COMPARATOR

l

OOk

Htl

10kHz

1MHz

INPUT

FROM

ru

....

1----.

~

ru

MODULATED

OSC

•

..

10 I

~10

1

CONTROL

VOLTAGE

A. F .C

TO

MOD

OSC

VVC - 1

FIG

6

BLOCK

FUNCTIONAL

DIAGRAM

REFERENCE OSCILLATOR

GENERATOR

·6·

Q

-3

is

a

shaping

amplifier

which

changes

the

essen-

tially

sinewave

output

of

Q-2

to

square

wave.

output,

compatible

with

the

TTL

circuitry

which

follows.

Q-3

is

heavily

driven.

Its

grounded-emitter

configuration

produces

square

wave

outputand

drives

IC-l,

a

decade

counter.

The

output

of

IC-l

(880-1080

kHz

range)

dri-

ves

IC-2,

another

decade

counter.

Its

output

frequency

is

in

the

88-108

kHz

range.

This

signal

is fed to

one

of

the

inputs

of

the

phaselock-Ioss

alarm

phase

com-

parator

as

well

as

to

a

third

decade

divider,

IC-3,

in

the

reference

oscillator

divider

chain.

The

output

of

IC-3

is

in

the

8.8

to

10.8

kiloHertz

range

andisthere-

ference

input

to

Q-4

of

the

main

channel

phase

compa-

rator.

Decade

dividers

IC-4

and

IC-5

divide

the

880-

1080

kHz

range

carrier-frequency-derived

pulses

from

the

modulated

oscillator

module

to

the

8.8-10.8

kHz

range

and

is

the

carrier

derived

input

to

Q-50f

the

main

channel

phase

comparator.

Q-4

and

Q-5,

connected

as

a

NAND

gate,

comprise

the

main

channel

phase

compa-

rator.

Both

Q-4

and

Q-5

are

heav

i

Iy

overdri

ven

by

the

respective

reference-derived

frequency

and

carrier-

frequency

derived

input

pulses

and

produce

symmet-

rical

square

waves

at

the

paralleled

collector

output.

When

the

carrier-derived

pulses

are

exactly

in

phase

with

the

reference

generator

pulses,

the

output

of

Q-4

and

Q-5

wi II be a

perfect,

50%

duty

cycle,

square

wave

varying

from 0

to

5

volts,

or

averaging

2.5

volts.

Any

departure

from

exact

phase

coincidence

between

the

two

input

signals

will

produce

!Square

wave

output

of

greater

or

lower

than

50%

duty

cycle.

This

results

in

an

average

output

voltage

above

or

below

the

2.5

volt

value.

This

comparator

DC

output

voltage

feeds

a

combination

prase-to-voltage

converter

and

loop

fi

Iter,

consisting

of

Q-6,

Q-7, Q-8,

and

Q-9.

Q-7

acts

as

a

constant

cur-

rent

saurce

which

charges

C-14

to

generate

a ramp.

0-6

operates

as a

switch

to

set

the

initial

voltage

on

C-14

at

zero.

Q-8

switches

the

current

source

on or

off

when

the

input

signal

goes

high

or

low,

respective-

ly.

Q-9

serves

as

an

output

emitter

follower.

It

mini-

mizes

the

loading

on

C-14

while

chargin~

the

output

100kHz

SQUARE

WAVE

IN

PU

T

IN

PUT

FROM

MODULATED

OSC

MODULE

~

-

7.5kHz

LOW

PASS

FIL

TER

0-7500Hz

-

...

DETECTOR

01.

02

OSC

Q4

fo-900kHz

2

-

@®lJ(Q)I·

filter.

Thus

the

Q-6, Q-7,

Q-8

and

Q-9

circuitry

oper-

ates

as

a

DC

loop

fi

Iter

or

integrator,

converting

phase

differentials

at

the

phase

comparator

input

into

a

DC

output

voltage.

This

output

voltage

is

fed

through

the

"lock"

switch,

SW-l,

to

the

modulated

oscillator

fre-

q

uency

control

input

and

corrects

any

difference

be-

tween

the

reference-oscillator-derived

and

the

modu-

I

ated-os

ci

Ilator-deri

ved

compari

son

frequenc

i

es.

The

modulated

oscillator

"free-running"

frequency

may

be

adjusted

by

the

front

mounted

frequency

vern-

ier

control,

(R-30

on

modulated

oscillator

module)

by

placing

the

front

panel

lock

switch

in

its

off

position.

Q-l0

and

Q-ll

comprise

the

phase

comparator

for

the

phase

lock

loss

alarm

circuit.

It

operates

at

100

kHz

(carrier-derived

input

from

IC-4

and

reference-oscil-

lator-derived

input

from

IC-2)

in an

identical

manner

to

the

10kHz

phase

comparator,

Q-4

and

Q-5.

However,

the

output

of

the

Q-l

0,

Q-ll

comparator

is

not

fi

Itered

to

DC.

When

the

two

100

kHz

input

signals

are

pre-

cisely

in

phase,

100

kHz

square

waves

appearat

the

output

of

the

comparator.

If

the

frequency

or

phase

of

the

input

signals

vary,

the

resultant

100

kHz

pulses

'

are

modulated

by

the

AC

component

resulting

from

the

l

difference

in

the

input

frequencies.

As

an

example,

l

assume

a

departure

of

1.0

kiloHertz

from

an

operating

l

frequency

of

100

MHz.

This

would

represent

0.1

Hertz

(1

x 10 3

-:-

1 x

10

4 =1 x 10-1)

difference

at

the

main

channel

phase

comparator

operating

at

10kHz.

This

normally

would

result

in

a

correction

voltage

to

return

the

modulated

osci

Ilator

to

produce

a

precise

100

MHz

output.

If,

for

some

reason,

this

does

not

occur,

the

100

kHz

comparator

wou

Id

produce

c s

lip

frequency

of

ten

times

0.1

Hertz

or

1.0

Hertz(10

3

-:-

103=1 x

100)

.

The

100

kHz

square

wave

signal,

interrupted

at

a

1.0

Hertz

rate

would

be

fed

to

the

alarm

module,

the

cir-

cuitry

of

which

responds

to

input

frequencies

up

to

7,500

Hertz

representing

a

carrier

frequency

error

of

7.5

MHz

at

the

100

MHz

operating

frequency.

Alarm

and

Control

Module

See

Figure

7

and

schematic

Diagram

Dwg.

Ii 550161/1.

The

a

larm

and

control

module

contains

circuitry

to

-

~

:

-

J

RELA

Y

3 STAGE KI

...

DC

AM

P -

Q1

Q2 Q3

LED~LQ.~~

O

-:

FIG.7

BLOCK

FUNCTIONAL

DIAGRAM

ALARM

8.

CONTROL

MODULE

11

/ 73 -7-

alert

the

operator

to

loss

of

phase

lock

and

to

disable

the

unit

if a

frequency

deviation

in

excess

of

100

kHz

occurs.

The

output

of

thE:

100

kHz

phase

comparatOr,

located

in

the

reference

generator

module

is

fed

to

a

7.5

kHz

low

pass

filter,

FLI.

This

filter

eliminates

any

100

kHz

components

produced

by

the

100

kHz

phase

com-

parator

and

passes

only

the

low

frequency

slip

fre-

quency,

which

would

be

present

in

the

event

of

loss

of

the

phase

lock

condition.

The

low

freq

uancy

sine

wave

output

of

the

fi

Iter

is

detected

and

converted

to

a DC

voltage

which

turns

off

transistor

Q-l.

Thisaction

switches

Q-2

on

and

Q-3

off.

When

Q-3

is

turned

oH,

co

Ilector

current

de-energ

i

zes

re

lay

K-l

and

turn

s

the

LED

lock

indicator

"off".

The

contacts

of

K-l

(rated

at

1.0A,

28

VDC),

appear

on

the

rear

terminal

barrier

strip

of

the

exciter.

This

termination

may

be

used

to

operate

an

external

visual

or

aural

alarm,

indicating

a

loss

of

phase

lock.

Alarm

loads

in

excess

of

25

watts

shou

Id

be

operated

by a

slave

re

lay

actuated

by

the

exciter

relay

contact

closure.

R-5

is

a

sensitivity

con-

trol

permitting

adjustment

of

the

threshold

condition

of

DC

amplifier,

Q-l,

Q-2, Q-3,

to

a

point

sufficiently

sensitive

to

insure

early

detection

of

loss

of

phase

lock.

Loss

of

phase

lock

does

riot

necessarily

result

in

an

ouf-of-tolerance

operating

frequency,

However,

the

center

frequency

should

be

closely

monitored

in

the

absence

of

phaselock

and

frequenty

corrections

should

be

made

manually.

The

100

kHz

comparison

frequency

represents

a

division

of

the

carrier

frequency

by a

fac-

tor

of

1000

times.

A

carrier

frequency

error

of

1000

Hz

produces

a 1 Hz

signal

at

the

output

of

the

7,5

kHz low

pass

filter.

The

detector

responds

to

a loS!!

of

lock

condition

of

7500

x

1000

or

an

error

of

up

to

7.5

MHz

at

the

carrier

frequency.

Since

it

is

possible

to

oper-

ate

on

frequencies

which

when

divided

by

10,000

pro-

duce

submultiples

suitable

for

phase

lock,

a

second

backup

system

is

employed

to

prevent

off-frequency

operation.

Refer

to

the

Alarm

Module

Block

Diagram,

Fig.

7.

A

crystal

oscillator,

Q-4,

operates

at

a

frequen-

cy

of

carrier

frequency

-

900

kHz.

2

The

oscillator

output

frequency

is

doubled,

then

mixed

with

an

operating

frequency

signal

fed

from

the

modu-

lated

oscillator

module.

The

RF

input

from

the

modu-

lated

oscillator

module

is

amplified

by

the

field

effect

R F

IN

PUT

APR

OX

1 4W

RF

AMP

Q1

RF

AMP

Q2

transistor,

Q-5,

and

fed

to

mixer,

Q-6.

The

900

kHz

intermediate

frequency

output

of

Q-6

is

amplified

by

Q-7.

Q-7

drives

a

900

kHz

band

pass

filter.

The

fil-

ter

provides

a

900

kHz

IF

output

signal

to

the

diode

detector,

D-6,

D-7.

If

the

operating

frequency

should

shift

by

100

kHz

or

more

(resulting

in a

mixer

output

frequency

100

kHz

removed

from

the

norma I

900

kHz,

IF),

the

voltage

at

the

filter

output

wi

II

decrease

suf-

ficiently

to

allow

Q-8

to

turn

on.

If

Q-8

turns

on,

Q-9

is

turned

off

and

Q-l0

is

turned

on.

The

collector

cur-

rent

of

Q-l0

en

erg

i

zes

re

lay

K-2

and

opens

the

re

lay

contacts

appearing

on

connector

terminals

8

and

10.

The

normally

closed

contacts,

8

and

10,

connect

DC

supply

voltage

to

the

power

amplifier

module.

This

relay

contact

closure

is

by-passed

by a

microswitch,

mounted

On

the

main

frame,

which

operates

if

the

alarm

module

is

removed

from

the

mounting

frame

for

service

or

maintenance.

RF

Power

Amplifier

Module

See

Figure

8

and

schematic

diagram

Dwg.

::t

552073/1.

The

two-stage

RF

power

ampl

i

fi

er

i

ncrea

ses

th

e a

pprox-

imately

0.25

watt

output

level

of

the

modulated

oscil-

lator

module

to

a

rated

10

watts

output

level,

and

ty-

pically

will

deliver

up

to

15

watts

output

power

into

a

properly

matched

50

ohm

load.

The

RF

input

to

the

first

stage,

Q-l,

is

fed

through

the

drive

control,

R-l

and

an

impedance

matching

net-

work

comprised

of

Cl,

C2

and

ll.

The

output

circuitry

of

Q-l

matches

the

input

impedance

of

Q-2,

the

final

output

stage.

The

RF

output

from

Q-2

appears

at

a

push-on

coaxial

output

connector

at

the

rear

of

the

module.

RF

output

is

sampled

by

diodes

Dl

and

D2

to

provide

a

relative

power

output

level

indication.

The

total

collector

current

of Q-l

and

Q-2

passes

through

a

.47

ohm

resistor,

R4.

The

voltage

developed

across

this

resistor

is

fed

to

the

front

penel

meter

when

the

DC

meter

switch

is

in

the

Ipa

pOsition.

The

RF

output

power

is

adjustable

by

Rl

over

a

range

of

approximately

2

to

15

watts

by

varying

the

RF

input

level

from

the

modulated

oscillator

module.

An

RF

on/standby

switch

SW-l

is

provided

on

the

front

panel

of

the

RF

module.

Thi

s

permits

removal

of

RF

power

from

the

equipment

following

the

exciter

without

dis-

abling

the

complete

exciter.

The

+ 24V DC

supply

voltage

for

the

RF

power

amplifier

can

be

interrupted

RF

REFERENCE

OUTPUT

l-lSW

RF

OUTPUT

FIG.

B

BLOCK

FUNCTIONAL

DIAGRAM

RF

POWER

AMPLIFIER

-8-

11/73

at

several

points

in

the

exciter

system,

as

shown

on

the

Main

Functional

Block

Diagram.

1)

The

rear

term

ina

Is

TB-2,

1

and

2;

2)

Channel-loss

relay

contacts

on

the

alarm

and

control

module;

3)

Main

frame-mounted

micros

w

itch

(

actuated

when

alarm

module

is

removed);

4)

Standby

switch

on

the

RF

power

amplifier

Mod-

ule.

CAUTION:

1)

Although

the

RF

power

amplifier

can

operate

under

normal

conditions

without

a

50

ohm

RF

load,

good

engineering

practice

dictates

that

the

RF

amplifier

be

operated

with

a

suitable

RF

load

with

a

voltage

standing

wave

ratio

of

less

than

2: 1.

This

VSWR

represents

a

transmission

efficiency

of

89

%;

2)

Use

extreme

care

in

inserting

or

removing

the

RF

Amplifier

Module

to

av

oid

damage

to

the

push-on

coax

connectors.

If

mi

sa

I

ignment

occur

s,

remove

the

rear

pa

ne

I

of

the

exc

iter

and

rea

Iign

the

con

nector

s on

the

ir

respective

mounting

bracket

by

loosening

the

connec-

tors

mounting

hardware.

Carefully

insert

the

module,

then

retighten

the

hardware

securing

the

coaxial

con-

nectors

to

the

frame

.

Power

Supply

Regulator

Module

See

Figure

9

and

schematic

diagram

(Dwg.

:;

552074

/

l)

.

The

power

supply

regulator

provides

all

the

required

DC

supply

voltages.

Four

separate

regulators

ore

in-

corporated

in

the

module

.

These

include

a +5

volt

supply

for

all

logic

devices

and

phase

comparators.

A-5

.2

volt

supply

feeds

the

high

speed

100

MHz

decade

divider,

IC-1,

of

the

modulated

oscillator

module

. A

+15

volt

supply

powers

all

other

modules

except

the

RF

power

amplifier

.

Power

to

the

RF

power

ampl

i

fier

is

supplied

from a

+24

v

olt

source

.

Transistors

Q-1

and

Q-2

act

as

a

Darlington

regulato

r

with

an

overload

current

protection

ci

rcuit,

consi

sting

of

D-

1,

D-2,

and

D-3.

Current

drawn

through

the

0.

27

ohm

series

resi

stor,

R-11

develops

a

voltage

drop

suf

-

ficientto

allow

current

atthe

bose

of

Q-1

to

be

drained

12 V I A

CT

~o@l](Q)I·

from

the

base

through

the

load,

thus

preventing

the

Darlington

combination

Q-1,

Q-2

from

being

turned

on.

The

two

forward

biased

diodes,

D6

and

D7

in

series

with

the

5 .6

volt

zener

diode,

Z-3,

increase

the

refer-

ence

voltage

sufficiently

to

overcome

the

DC

voltage

loss

of

Q-1,

Q-2

.

The

DC

output

voltage

should

be

5V, ± 10%,

as

measured

with

a

high

quality

DC v

olt-

meter.

The

DC

meter

provided

on

the

front

ponel

of

the

exciter

should

be

used

as

a

reference.

In

the

event

of

a

discrepancy

between

the

front

panel

meter

reading

and

the

specified

+5

volts,

verify

the

reading

by

meas-

urement

of

the

actual

voltage

at

the

modules

.

The

operation

of

the

-5

.2

volt

supply,

with

Q-3,

Q-4

regulators,

is

simi

lar

in

operation

to

the

+ 5

volt

supply

with

the

exception

of

the

current

shutdown.

Refer

to

the

schematic

diagram

for

nominal

voltage

v

alues.

The

+

15

volt

supply

uses

regulator

circuitry

similar

to

that

used

in

the

+5V

supply.

This

supply

is

a

rela-

tively

high

current

supply.

The

output

voltage

should

be

measured

with

all

modules

properly

inserted

.

Trans-

i

stor

Q-6,

an N

PN

power

de

vi

ce,

is

mounted

on

the

metal

chass

is

of

the

power

supply

regulator

and

is

i

nsulated

from

the

chass

is

with

a

mica

washer

.

Q-7

and

Q-8

operate

as

Darl

ington

pass

tr'ansi

stors

in

the

+

24

volt

supply

.

These

transistors

ore

mounted

on

the

externa

I

heat

sink

located

on

the

top

of

the

main

chassis.

Q-7

and

Q-8

receive

a

base

reference

voltage

from

Z-l.

The

24

volt

supply

is

current

limited

at

approximately

1.

25A,

well

above

the

maxi

mum

current

requirements

of

the

RF

power

amplifier.

A

1.5A

fuse,

F1,

is

provided

between

the

rectifier

diodes

and

the

regulator

to

protect

the

power

transformer

if a fai

lure

occurs

in

the

regulator

section

.

All

voltages

to

the

power

module

are

supplied

by a

common

power

trans-

former

with

three

separate

secondary

winding

.

See

the

Main

Block

Functional

Diagram

for

the

proper

power

transformer

connections

and

power

supply

intercon-

nection

wiring.

IS

r

3SV

• •

TOR

E

LA

YS

1.6A

11

/

73

POWER

TRANSFORMER

TO

OVEN

FIG

.9

BLOCK

FUNCTIONAL

DIAGRAM

POWER

SUPPLY

REGULATOR

-9-

Meter

Ampl

ifier

and

Switching

See

Figure

10

and

schematic

diagram

(Dwg. #551049/1).

The

meter

amplifier,

located

behind

the

front

meter

panel,

is

used

to

amplify

the

various

audio

frequency

modulation

signals

sufficiently

to

drive

the

front

panel

VU

meter.

This

is

accessible

by

removal

of

the

top

cover

plate.

Q-1

provides

ampl

ification

to

drive

the

emitter

fol-

lower,Q-2.Q-3functions

as

aDC

meter

drive

amplifier.

Rectification

of

the

DC

signal

takes

place

in

the

base

circuit

of

Q-3.

The

transistor

operates

as

an

emitter

follower

with

the

meter

connected

to

a

tap

on

the

emit-

ter

resistor.

Since

the

meter

is DC

coupled,

a

small

amount

of

DC

flows

through

the

meter

to

ground.

To

compensate

for thi s

voltage,

a

reverse

voltage

is

ap-

plied

to

the

opposite

side

of

the

meter

through

the

adjustable

1K

ohm,

zero

adjust

potentiometer,

R-14.

The

input

calibrate

control,

R-1,

sets

the

overall

gain

·

.'

of

the

amplifier

so

that

100%

modulation

corresponds

to

a

zero

VU

reading

on

the

meter.

Model

B-1l2Stereo

Generator

Module

(Dwg. '0'559048/1)

The

stereo

generator

module

utilizes

a

switching

meth-

od

of

generating

a

stereo

composite

signal.

The

prime

advantage

of

this

method

is

simplicity

of

adjustment

and

excellent

stereo

separation.

Transistor

Q-6,

a

cry-

stal

oscillator,

operates

at

76 kHz.

Its

output

is

loose-

ly

coupled

to

Q-7,

a

buffer

stage,

operating

as

an

emit-

ter

follower.

The

output

of

Q-7

drives

a

shaping

am-

plifier,

Q-8.

Q-8

is

heavily

overdriven,

resulting

in

square

wave

output.

The

collector

voltage

of

Q-8

changes

from

the

full

supply

voltage

value

to

zero

voltage

at

a

76

kHz

rate.

Thi

s

square

wave

76

kHz

si~nal

drives

switching

integrated

circuit,

IC-1. IC-1

provides

a

dual

function.

It

divides

the

76 kHz

signal

by

four

to

19

kHz for

pilot

carrier

output

and

secondly,

provides

two

38

kHz

signals

which

are

precisely

180

degrees

out

of

phase.

The

two 38 kHz

out-of-phase

sq

uare

wave

voltages

drive

Q-1

and

Q-2.

Q-1

and

Q-2

operate

as

high

impedance

shun!

ing

switches.

They

COMPOSITE

IN

1

f

IN

PU

T

CONTROL

J

1 aI

GAIN

ST

AGE

l

J --'" 02

EMITTER

FOLLOWER

alternately

switch

out

a

segment

of

the

audio

input

signal

coming

from

the

input

terminal

s

of

the

module.

When Q-1

is

turned

on, Q-2

is

turned

off.

When Q- 1

is

in

its

"on"

state,

the

input

signal

from

terminals

9

and

10

is

shunted

to

ground,

hence

cannot

reach

the

composite

amplifier,

Q-3.

During

the

same

time

inter-

val,

Q-2

is

turned

off

and

an

input

signal

on

terminals

13-14

can

reach

Q-3.

250

ohm

controls,

R-11

and

R-12,

in

the

collector

leads

of

Q-1

and

Q-2,

serve

to

balance

the

attenuation

of

the

two

transistor

switches.

Correct

setting

of

these

controls

wi

II

be

covered

in

the

Cal

i-

bration

and

Operation

section

of

the

manual.

The

com-

bined

signal

in

Q-3

consi

sts

of

the

chopped

signal

from

terminals

13-14;

the

19 kHz

pi

lot

which

is

now a

sine

wave

derived

from IC-1

through

a 19 kHz

fi

Iter;

plus

many

harmonics

generated

in

the

square

wave

switching

process

of

Q-1

and

Q-2.

The

composite

sig-

nal

out

of

Q-3

is

filtered

by

a

53

kHz

low

pass

filter,

located

on

the

lower

top

cover

of

the

unit.

This

filter

is

properly

matched

by

the

input

and

output

ci rcu i

ts

to

produce

a

constant

group

delay

over

the

frequency

range

of

the

fi

Iter.

The

output

of

the

fi

Iter

is

connected

to

Q-4,

a

simple

gain

stage,

and

Q-5,

an

emitter

fol-

lower,

providing

a low

impedance

output

to

drive

the

modulator.

A front

panel

pilot

phase

control,

R46,

ad-

justs

the

phase

of

the

transmitted

19

kHz

pilot.

This

function

insures

proper

timing

of

the

transmitted

pi

lot

and

the

transmitted

38

kHz

switched

composite

signal.

The

amp

Ii

tude

of

the

pi

lot

is

norma

Ily

set

at

1I10th

the

level

of

the

composite

signal.

Thus

100%

total

modu

lation

would

include

10%

injection

of

the

19 kHz

pilot

carrier.

This

amplitude

is

established

by

a

front

panel

pi

lot ampl

itude

control,

R-47.

The

19 kHz

pi

lot

carrier

may be di

sabled

by

a

front

panel

switch,

SW-1,

placing

the

system

in a

monaural

mode.

In

monaural

operation,

the

audio

input

signals

at

terminals

9-10

and

13-14

are

resi

stively

combined,

adjusted

in

level

and

connected

directly

to

Q-4

and

Q-5

to

feed

the

monaural

signal

to

the

modulated

os-

cillator

module.

The

above

switching

is

accomplished

by a

relay

located

on

the

module

itself.

The

relay

can

03

OETECTOR

AND

METER

DRIVER

~r---7lH

D.C

TO

~L....LJ

ZERO

METER

FIG

10

BLOC·K

FUNCTIONAL

DIAGRAM

METER

AMPLIFIER

-10-

11/73

be

controlled

by

the

front

panel

switch,

or

remotely

by

an

externally

connected

switch

closure

across

ter-

minals

TB-2,

7

and

8.

The

front

panel

control

must

be

in

the

mono

position

for

remote

selection

of

the

mono/

stereo

modes.

Model

8-113

SCA

Generator

(Dwg.

It

559049/1)

The

SCA

Generator

(Module

position

2

or

3)

is

avai

1-

able

on

two

standard

frequencies,

either

41

kHz or

67

kHz.

Dual

transistor

Q-3

(a

matched

silicon

pair)

func-

tions

as

the

free-running

master

oscillator.

The

fre-

quency

is

primari

Iy

determined

by

the

time

constant

of R-16,

R-20,

C-S,

C-8

and

the

voltage

appl

ied by

the

pos

ition

of

R-10,

the

coar

se

adj

ustment,

and

R-ll

the

front

panel

fine

adjustment

.

The

audio

modulating

signal

is

also

applied

to

the

bases

of

Q-3.

The

audio

is

frequency

bandwidth

limited

by

filter

FL-1,

The

out-

put

of

FL-1 is

connected

to

a 1K ohm

potentiometer,

R-3,

which

acts

both

as

a

load

to

the

fi

Iter

and

as

the

modulation

level

control

.

The

following

two

stages,

Q-1

and

Q-2,

serve

as

an

ampl

ifier

and

emitter

fol-

lower

to

provide

the

necessary

level

and

pre-emphasi

s

to

properly

modulate

Q-3.

C-2

produces

the

necessary

pre-emphasized

frequency

response

by

increasing

the

gain

of

Q-1

as

the

modulation

frequency

is

increased.

The

output

of

Q-3

is

a

41

kHz or

67

kHz

square

wave

frequency

modulated

signal

which

is

coupled

to

emit-

ter

follower

Q-4,

through

a DC

voltage

controlled

swi

tch

consisting

of

R-21, R-22, R-23,

and

D-6, D7.

The

resistor

diode

switch

is

used

to

provide

a

silent

mut-

ing

circuit.

The

67 or

41

kHz sq

uare

wave

signal

out

of

emitter

follower

Q-4

must

be

filtered

by

FL-2

before

beIng

transmitted

.

FL-2

eliminates

the

unwanted

square

wave

harmonics

and

produces

a

clean

subcarrier

con-

sisting

only

of a

frequency

modulated

sinusoidal

wave-

form.

To

prevent

undesirable

loading

of

the

low

pass

filter,

Q-S,

an

emitter

follower

provides

the

necessary

isolation.

The

output

level

from

Q-S

is

controlled

by

potentiometer

R-29

to

vary

the

SCA

sub

carrier

injec-

tion

level.

The

emitter

of

Q-2

is

connected

to

a

2.SK

control,

R-9,

and

adjusts

the

modulation

voltage

level

to

the

input

of

Q-7.

Q-7

functions

as

a

limiter

ampl

ifier.

Q-7

pro-

vides

40dB

of

limiting

to

the

sampled

modulating

volt-

age.

The

limiter

output

voltage

is

rectified.

The

rec-

tified

DC

output

voltage

is

used

to

turn

on

the

elect-

ronic

mute

switch,

R-21,

R-23,

D-6,

and

D-7.

The

mute

voltage

is

bled

off

to

ground

through

the

R-44, C-21

combination

which

functions

as

a var

iable

mute

delay

circuit.

The

presence

of

the

mute

voltage

turns

trans-

istor

Q-8

on,

allowing

current

to

flow

through

the

LED

indicating

lamp

mounted

external

to

the

SCA

module.

Thet

35-40

volt

unregulated

source

voltage

is

filtered

and

regulated

by

trans

i

stor

Q

-6.

11173

~°®lJ(Q)I·

V.

OPERATION

Turning

on

Exciter

Place

the

PA

drive

control

located

on

the

RF

Power

Amplifier

module

in

its

extreme

counterclockwise

posi-

tion.

Connect

AC

power

to

terminals

TB-1,

1

and

2.

Connect

a

SO

ohm load

to

the

exciter

RF

output

jack.

Actuate

power

switch.

Check

DC

meter

readings

by

switching

to

the

tSV,

-SV,

t

lSV,

and

+24V

positions

to

insure

proper

operation

of

the

power

suppl

ies.

Obtaining

Phaselock

Rotate

the

meter

switch

to

the

phase

lock

position.

In

this

position,

the

output

of

the

10

kHz

phase

compara-

tor

is

connected

to

the

meter

through

a

4.7

K

calibra-

tion

resistor,

R-14A.

Turn

the

exciter

off

momentarily

while

observing

the

phase

lock

meter.

Once

again,

turn

on

the

exc

iter.

The

meter

shou

Id

come

up

to

near

100%. Within

15

seconds,

the

meter

will

quiver

as

the

modulated

osci

Ilator

approaches

the

lock

freq

uency.

Slow

oscillation

of

the

meter

needle

is

due

to

the

pres-

ence

of

the

AC sl ip freq

uency

signal.

As

lock

is

auto-

matically

attained,

the

quivering

wi

II

stop

abruptly

and

the

LED

indicator

on

the

alarm

module

wi"

come

on a

few

seconds

later.

To

verify

pro,Per

phase

lock,

adjust

the

50

MHz

vernier

freq

uency

control

R-30

(located

on

the

modulated

oscillator

module

front

panel)

slowly

to

the

left,

then

to

the

right.

The

meter

should

follow

the

control

negatively,

then

positively.

If

phase

lock

is

not

attained,

the

meter

wi

II

not

follow

the

vernier

control.

Check

to

be

certain

the

phase

lock

switch

on

the

reference

generator

is in

the

lock

pasition.

If

the

vern

ier

frequency

control

ha s

been

improper

Iy

ad

j

usted

or

the

unit

is

extremely

cold,

cantinue

to

slowly

adjust

the

vernier

frequency

control

from

one

extreme

to

the

other

until

lock

is

attained

and

the

meter

follows

the

rotation

of

the

control.

After

lock

is

attained,

rotate

the

control

to

position

the

meter

at

100%.

This

wi

II

assume

goodrelock

if a

loss

ofAC

power

occurs.

After

a

few

hours

of

operation,

recheck

the

phase

lock

posi-

tion

for 100%

reading.

Setting

the

Station

Frequency

No

attempt

to

adjust

the

station

frequency

should

be

made

unti

I

the

system

is

phase

locked,

and

has

bee

'n

in

operation

long

enough

to

reach

normal

operating

temperature.

Allow

30

minutes

for

the

crystal

oven

temperature

to

stabi

Ii

ze.

The

fron t

pane

I

frequency

control

on

the

reference

osci

lIator

module

is

used

to

adjust

the

freq

uency

to

a

properly

calibrated

frequency

monitor

or

to

concur

with

measurements

taken

by a

frequency

measuring

service.

Adjusting

the

RF

Output

With a

properly

matched

50

ohm

load

connected

to

the

output

of

the

B-910

FM

exciter,

flip

the

RF

on/

standby

-

11

-

switch

located

on

the

RF

Power

Ampl

ifier

Modu

Ie to

the

"on"

po

sit

ion .

Adjust

the

PA

drive

control

clockwise

while

monitor-

ing

the

Ipa

meter

position.

VI.

CALIBRATION

PROCEDURES

REFERENCE

GENERATOR

MODULE

(

Reference

Osci

lIator)

Place

the

reference

generator

module

on

the

module

extender

card.

1.

Turn

meter

switch

to

the

Reference

Oscillator

posi-

tion.

The

meter

is

a

0-1

ampere

meter

in thi s

position,

100%

corresponding

to

lA.

As

the

PA

drive

is

increased,

the

RF

output

wi

II

increase.

Advance

the

drive

con-

trol

until

the

desired

RF

o~tput

is

achieved.

In

no

case

2.

shou

Id

the

fina

I

current

read

in9

exceed

1

ampere.

Normally

an

RF

output

of

10

watts

is

achieved

with

3.

approximately

600-900

milliamperes

of

PA

Current.

The

PA

position

scales

the

meter

to

a

0-28

volt

DC

4.

meter

and

is

only

used

as

a

reference.

After

the

pro-

Adjust

inductor

L-l

for maximum

reference

oscil-

lator

voltage.

Pos

iti

on

the

frequency

ad

j

ustment

control

on

the

front

of

the

module

to

its

mid-position.

Connect

a

frequency

counter

to

the

collector

of

Q-3

or

observe

the

frequency

of

the

exc

iter

with

an

FCC

type-approved

frequency

mon

itor.

The

frequency

should

be

within

1 kHz

of

the

desired

frequency.

If

the

frequency

deviation

is

greater

than

1

kHz;

ro-

tate

the

slug

in

inductor

L-l

in

the

appropriate

direction

to

bring

the

frequency

closer

to

the

de-

sired

frequency.

This

will

insure

sufficient

tuning

range

wi th

the

front

contro

I,

to

permit

long-term

frequency

correction.

per

output

is

obtained,

either

connect

an

in-line

RF

wattmeter

in

series

with

the

output

coaxial

I

ine

and

adjust

the

PA

tune-loading

controls

for maximum RF

output

power,

or

adjust

the

loading

control

for minimum

Ipa

current.

Either

procedure

wi

II

result

in a

resonant

cond

ition

for

the

power

ampl

ifier

output

network.

Monaural

Audio

Connect

a

400

Hertz

audio

source

to

the

proper

input

terminals

located

on

the

rear

of

the

exciter.

The

audio

signal

level

feeding

the

exciter

should

be

approxi-

mately

+

10dbm.

Position

the

flat

Ipre-emphasis

switch

located

on

the

front

of

the

module

to

the

pre-emphasi

s

position.

Adjust

the

audio

level

to the.

exciter

for

the

desired

percentage

of

modulation

os

indicated

on an

FCC

type-approved

modulalion

monitor.

Alternatively,

position

the

front

panel

meter

switch

in

the

audio

posi-

tion

and

adjust

the

level

accordingly.

The

meter

is

a

semi-peak

reading

device

and

is

calibrated

to

display

100%

modulation

with

a

sine

wave

audio

input

signal.

When

feeding

complex

wave

program

material,

allowance

must

be

made

to

maintain

modulation

peaks

below

the

100%

modulation

point

since

a

semi-peak

meter

cannol

respond

to

intermittent

peaks

of

short

duration,

as

ex-

perienced

wi

th norma I

program

materi

a

I.

Stereo

Operation

Audio

Conr.Ject

suitable

sources

of

audio

to

the

left-

and

right-

channel

terminals

on

the

rear

af

the

B-910

exciter;

left

input,

TB-3,

5

and

6;

right

input,

TB-3,

7

and

8.

Adjust

the

levels

as

described

in

the

monaural

section.

Pi

lot

Level

Remove

the

audio

from

the

exciter.

With a

properly

ad-

justed

FCC

type-approved

modulation

monitor

capable

of

measuring

the

19

kHz

pilot

injection,

adjust

the

pi

lot

level,

located

on

the

front

panel

of

the

stereo

gen-

erator

modu Ie for 8-10%.

-1

?-

5.

Adjust

the

Reference

Oscillator

calibration

pot

R-l

0

(lOOK) for a 100% '

ading

on

the

front

panel

meter.

REFERENCE

GENERATOR

MODULE

(Phase

to

Volt-

age

Converter)

1.

Connect

an

osc

i

II

oscope

to

the

.005

tanta

I

um

charg-

ing

capacitor,

C-14.

2.

With

the

system

in

phase

lock,

observe

the

wave

form

across

the

capacitor.

Slowly

advance

the

50

MHz

oscillator

vernier

until

the

system

loses

lock,

Just

prior

to

phase

lock

loss,

the

wave

form

should

be

similar

to

Fig.

11

below.

If

the

observed

wave

form

is

more

similar

to

that

shown

in

Fig.

12,

adjust

the

ramp

voltage

control,

R-19,

slightly

in

the

direction

which

lowers

the

ramp

amplitude

until

theglitch

on

the

leading

edges

is

eliminated,

as

phase

lock

is

lost.

This

control

normally

will

operate

in

its

full

clockwise

position.

----J

L-

I

--'

'--

FIG.

11

FIG.

12

11/73

MODULATED

OSCILLATOR

MODULE

Place

the

modulated

osci

lIator

module

on

the

extender

card.

1.

Turn

phase

lock

switch

off

(located

on

reference

generator

modu Ie).

2.

Position

the

vernier

frequency

control,

R-30,

in

its

mid-position.

3.

Position

meter

switch

in

phase

lock

position.

4.

Connect

a

suitable

100

MHz

frequency

counter

to

the

RF

output

jack

(J-l).

CAUTION:

A

pad

may be

required

between

the

exciter

output

and

the

counter

to

prevent

damage

to

the

latter

unit.

5.

Position

all

coil

slugs

(L-2,

L-6,

L-8,

L-ll,

L-14)

near

their

mid-position.

6.

Connect

a

100

MHz

oscilloscope

Or

RF

voltmeter

to

the

RF

output

jack.

7.

Slowly

adjust

the

oscillator

coil,

L-2,

and

watch

the

phase

lock

meter

for a low

frequency

beat.

Turn

the

coil

slug

very

slowly

as

it

is

possible

to

miss

the

beat.

Set

the

slug

as

close

to

the

zero

beat

in-

dication

as

possible.

8.

Flip

the

phase

lock

switch

on.

The

meter

.hould

snap

to a

steady

position

indicating

phase

lock

and

the

LED

lock

indicator

on

the

alarm/control

module

should

come

on

after

a

few

seconds.

9.

Observe

the

output

voltage

of

the

module.

Adjust

the

doubler

coil,

L-6,

for maximum 100

MHz

dUtpUt.

10.

Adjust

the

three

remaining

sluga

in

inductor~

L-8,

L-l1,

and

L-14,

for maxi

mum

Olltput.

The

tun

ing

of

these

inductances

wi

II

be

extremely

broad.

11.

Observe

the

frequency

on

the

counter

or

the

fre-

quency

mon itor.

The

frequency

shou

Id

be

the

de-

sired

carrier

operating

frequency.

12.

Remove

the

counter

and

repl

ace

wi

th a

47

ohm, 1-

watt

non-inductive

resi

stor.

13.

Adjust

the

series

output

coupling

capacitor,

C-37,

for maximum

output.

The

final

RF

voltage

output

should

be

between

3

and

5

volts

across

the

47

ohm

res

i

sti

ve

load.

MONAURAL AUDIO

MODULE

1.

Connect

an

accurate

signal

generator

with

either

internal

or

external

col

ibrated

attenuator

to

the

in-

put

termi

no

Is

and

on

output

vol

tmeter

of

flat

fre-

quency

response

over

a

SO

to

15,000

Hz

range,

to

the

output

terminals.

2.

Adjust

the

input

level

at

250

Hz

to

+

10

dBm.

3.

Set

an

output

level

reference.

4.

Vary

the

input

frequency

between

50

and

15,000

Hz,

recording

the

attenuation

of

the

input

signal

neces-

sary

to

maintain

a

constant

output

voltage.

The

at-

tenuation

settings

should

follow

closely

the

stan-

dard

75

mi

crosecond

pre-empha

sis

curve

as

shown

in

section

73.3330f

the

FCC

Rules

and

Regulations.

A

reproduction

of

the

standard

pre-emphasi

s

curve

is

included

following

this

section.

11173

~o@IJ(Q)I·

5.

If

the

measured

response

does

not

follow

the

pre-

scribed

curve,

the

pre-emphasis

may

be

altered

slightly

by

varying

the

value

of

the

nominal

1500

pf

capacitor,

C-6,

in

series

with

the

pre-emphasis

switch,

SW-l.

6. Do

not

alter

the

adjustment

of

the

15

kHz

low

pass

filter.

This

is

an

extremely

stable

filter,

precisely

adjusted

at

the

factory.

The

tuning

slugs

in

the

in-

ductor

sore

epoxi

ed

in

place

after

fi

na I

factory

ad-

justment.

ALARM AND

CONTROL

MODULE

Connect

the

alarm

and

control

module

to

the

extender

card.

Check

for

proper

frequency

crystal

in

the

alarm

module.

Use

the

formula

below

for

determining

the

pro-

per

frequency

of

the

crystal.

Fc(MHz} =

fo+900kHz

:2

Oscillator

Adjustments

or

Fc(MHz} =

fo-900

kHz

2

1.

Connect

a

voltmeter

with

a 5

volt

range

to

the

test

point

TP-l,

located

between

theoscillator

and

dou-

bler

coi

Is,

L-3

and

L-2.

2.

Adjust

the

slug

in

the

oscillator

coil,

L-3,

for

max-

imum

voltage

at

the

test

point.

Rotate

the

slug

in a

direction

to

increase

inductance

for maximum

volt-

age

reoding.

Adjust

the

slug

for a

reading

approxi-

mately

10·15%

below

the

maximum

voltage

obtained.

This

will

insure

reliable

crystal

starting

whenever

the

unit

is

turned

on.

Doubler

Adjustment

1. Adj

ust

the

doubler

coi

I,

L-2, for a

noticeable

dip

in

the

output

voltage

observed

at

the

above

test

point.

Set

the

slug

for

the

exact

minimum

reading.

The

final

voltage

reading

will

be

between

1

and

2

volts

DC.

RF Coi I

Ad

i

ustment

1.

Connect

an

oscilloscope

to

the

collector

of

trans-

istor,

Q-6,

(the

mixer),

Observe

the

900

kHz

inter-

mediate

frequency.

Adjust

the

RF

coi

I,

L-1,

for

maximum

900

kHz

output,

which

is

typically

2

volts,

peak-to-peak.

Off

Frequency

Detector

Threshold

1.

Temporarily

remove

the

crystal,

Xtal-1,

from

its

socket.

Adjust

the

K-2

threshold

control,

R-33,

to

the

point

where

the

coil

of K-2

just

energizes.

Re-

insert

the

crystal.

K-2

contacts

should

then

reopen,

(relay

de-energizes.)

-13-

Phase

Lock

Loss

Threshold

1.

Turn

the

phase

lock

switch

to

the

off

position.

Ro-

tate

the

vern

i

er

frequency

control

on

the

modu I

ated

oscillator

module

to

the

extreme

counterclockwise

are

zener

diode

referenced

and

no

calibration

adjust-

ments

are

required

or

possible

.

NOTE:

A

1)12

Amp

fuse,

F-1,

is

located

inside

of

the-

module

protecting

the

RF

Power

amplifier.

position.

2.

Adjust

the

loss

of

lock

threshold

control,

R-5,

until

relay

K-1

is

de-energized.

STEREO

GENERATOR

MODULE

1.

Place

the

stereo

generator

module

on

the

extender

3.

Turn

the

phase

lock

switch

to

its

on

position

. Ad-

card

provided.

Connect

an

FCC

Type

Approved

and

pilot

frequency

Monitor

to

B-910.

stereo

modulation

the

output

of

the

just

the

modulated

osci

Ilator

ver

,

nier

freq

uency

con-

2.

trol for

phase

lock.

After

approximately

3

seconds,

relay

K-1

should

energizes.

3.

Locate

the

left

and

right-channel

audio

input

ter-

minals

located

on

the

rear

apron

of

the

exciter.

Connect

an

audio

source

of

250

Hz

at

a +10 dBm

level

to

the

left-channel

audio

input

terminals

and

RF

POWER

AMPLIFIER

MODULE

Remove

the

RF

Power

Amplifier

cover,

reinsert

the

4.

modu Ie,

remove

the

Reference

Osc

i

Ilator

modu Ie

and

the

Alarm

and

Control

module

to

gain

access

to

the

RF

Ampl

ifier

.

1.

Connect

a

cal

ibrated

RF

wattmeter

to

the

RF

output

jack

(J-l)

on

the

rear

of

the

exciter.

2.

Connect

a

high

frequency

osci

Iloscope

to

the

RF 5.

output

Jack,

adjust

C-1, C-2, C-7,

C-8, C-13,

and

C-14

for a maximum

signal

as

shown

on the

watt-

meter,

and

simultaneously

observe

the

osci

Iloscope

to

ascertain

atthe

same

time

that

the

sinusoidal

RF 6.

waveform

as

displayed

shows

the

minimal

amount

of

harmonics

and

spurious

signals.

3.

Switch

the

DC

Meter

function

switch

to Ipa, a

read-

,' ing of

between

600

and

900

millamperes

should

be

7.

indicated.

8.

4.

Sw

itch

the

DC

Meter

sw

itch

to

I

pa,

a

read

i

ng

of be-

tween

22

and

24

volts

DC

should

be

indicated.

(If

correct

Ipa

and

Epa

readings

are

not

obtained,

re-

p,eat

step

2 unti I

correct

readings

are

obtained.)

9.

5.

Return

the

DC

Meter

switch

to

Epa

and

adjust

the

front

paMI

RF

Drive

control

until

a

reading

of

800

milliamperes

is

indicated.

The

RF

output

ot

this

reading

is

between

8

and

12

watts.

6.

Observe

the

indication

of

RF

output

power on

the

wattmeter

and

adjust

C-13

for maximum RF

output.

7. An RF

output

power of

10

watts

shou

Id

be

obtai

ned

with

a

total

lpo

current

of

less

than

900

milliamp-

eres

.

8.

Adjust

the

front

panel

RF

Drive

control

for

the

de-

si

red

RF

output

power

(10

watts

for a

B-910T

or

the

recommended

required

RF

drive

for

the

transmitter

for

which

a

B-910

is

being

used

as

an

exciter).

9.

Switch

the

DC

Meter swit"ch

to

the

RF

position

and

adjust

the

RF

Sample

Calibration

control,

R-6 for

a 100%

read

ing

on

the

meter,

The

RF

output

meter

reading

is

relative.

It

is

a

sampling

of

RF

voltage

and

is

not

a

precise

indication

of

RF

power.

A

cali-

brated

RF

wattmeter

terminated

with

a

non-inductive

50

ohm load

should

be

used

whenever

absolute

RF

power

readings

are

to

be

made.

POWER

REGULATOR

MODULE

All

output

DC

voltages

from

the

Powe

r

Regulator

Module

-14-

adjust

the

composite

output

level

control

for 100%

left

channel

modulation

indicated

by 100%

on

the

total

modulation

monitor

and

90% on

the

left

channel

meter

of

the

stereo

modulation

monitor.

Switch

the

stereo

modulation

monitor

to

monitor

the

19 kHz

pilot

injection.

Adjust

the

19

kHz

pilot

lev-

e I

contro

I

located

on

the

front

of

the

modu Ie for 10%

pilot

injection

.

Switch

the

signal

generator

to

100

Hz.

Parallel

the

left-

and

right-channel

audio

input

terminals

in

a

manner

wh

ich

wi

II

have

the

right

channel

out-of-

phase

with

the

left

(L =

-R).

Adjust

the

level

for 100%

total

modulation.

Connect

an

oscilloscope

to

the

composite

output

terminals

of

the

stereo

generator

module.

(

This

can

be

readi

Iy

connected

to

the

arm of

the

output

level

control,

R-31).

Observe

the

bow-tie

waveform

and

adj

ust

the

19

-

38

kHz

phasing

control,

located

on

the

fr

ont

of

the

stereo

generator

module,

to

phase

the

hori

zontal

arrow

heads

exactly

horizol1tal

to

each

ot

her

as

shown

below

in

Fig.

13.

(Fig.

'1

4, i

ncorrect

adjustment)

.

FIG.

14

11173

~°®lJ(Q)I·

10.

Feed

a

400

Hz

signal

to

the

left

channel

input.

sary)

of

the

19 kHz

signal

for

exactly

19,000

Hz,

± 0 Hz,

with

the

trimmer,

C-11.

11.

Adjust

the

oscilloscope

to

properly

synchronizeon

12.

13.

the

composite

waveform.

Adjust

the

left

channel

17.

amplitude

switch

control

for minimum

curvature

in

Connect

the

signa

I

generator

to

the

rear

aud

i0

ter-

minals

of

the

exciter

in

a

manner

which

will

feed

in-phase

signals

to

the

left

and

the

right

channels,

L = + R.

Measure

the

crosstalk

of

the

L + R

chan-

nel

into

the

L - R

channel

using

the

stereo

monitor

for

measurements.

Complete

the

above

across

the

50

-

15,000

Hz

spectrum.

the

base

line

as

shown

in

Fig.

15.

FIG.

15

Repeat

steps

9

and

lOw

ith

the

signa

I

generator

18.

Repeat

step

16

except,

connect

the

generator

to

feed

L=

- R

signals,

and

measure

the

crosstalk

of

L - R

into

L + R.

19.

Measure

the

suppressed

38

kHz

carrier

level.

This

should

be

below

1%.

20.

Position

the

front

panel

stereo-mono

switch

in

the

mono

position.

connected

to

the

right

channel

input

termi

no

ls.

Ad-21.

Adjust

the

monaural

gain

trimmer

control,

R-2, for

100%

reading

on

the main

channel

monitor with a

+10

dBm, 1000 Hz

signal

connected

totheleft

chan-

just

the

right

channel

amplitude

control.

Select

an

audio

frequency

near

10 kHz.

Observe

the

base

line

of

the

composite

wave

form.

Alternately

adjust

the

filter-matching

series

and

shunt

trimmers,

nel

input

terminals.

R-20,

and

R-24

for minimum

phase

error

and

straight

Front

Panel

Modulation

Meter

lines

as

shown

in

Fig.

16.

(Fig.

17,

improper

Remove

top

cover.

The

meter

ampl

ifier

located

in

the

compartment

directly

behind

the

meter

panel

has

two

calibration

adjustments.

1.

Remove

all

input

audio

signals

.

2.

Place

the

meter

select

switch

in

the

Audio

position.

3. T

emporar

i

Iy

remove

the

stereo

generator

modu Ie,

if

used.

4.

Adjust

the

DC

balance

control,

R-14,

located

on

the

meter

amplifier

card,

for

zero

reading

on

the

meter.

5.

Re-insert

the

stereo

generator

module

if

used,

and

modulate

the

transmitter

100%

with

a

1,000

Hz

sine-

wave

signal

as

indi

cated

by

a

cal

ibrated

modula-

tion

monitor.

6.

Adjust

the

input

cal

ibration

control

R-1 for

exactly

100%

as

indicated

on

the

front

panel

meter.

B-113

SeA GENERATOR

1.

Position

the

SCA

generator

module

on

an

extender

card.

2.

Connect

an

FCC

Type

Approved

SCA

frequency

and

modu

lation

mon

itor

to

the

output

of

the

B-910

FIG.

17

exciter.

14.

Check

the

stereo

audio

separation

using

the

stereo

3.

Adjust

R-10,

the

coarse

frequency

control

for

ex-

modulation

monitor

for both

left

into

right

and

right

actly

67

kHz

with

the

front

panel

fine

frequency

con-

into

left

measurements.

Separation

should

be

greater

trol

positioned

approximately

in

the

mid-position.

than

35

dB for

all

freq

uenci

es

between

50

Hertz

4.

Pos

i

tion

the

l

flat

/

pre-empha

sis

swi

tch

in

the

II

fl

at"

and

15

kHz.

position.

15.

Recheck

steps

3

and

4.

This

will

be

the

final

ad-

5.

Connect

an

audio

signal

source

of

1000 Hz,

+10,

justment

of

the

pilot

level

control

and

composite

±2,

dBm,

to

the

rear

audio

input

terminals

.

output

level

adjustment.

6.

Adjust

R-29,

the

Injection

Level

control

for 8-10%

16.

Check

the

frequency

of

the

19 kHz

pilot

connect-

modulation

as

indicated

on

the

SCA

monitor.

ing a

frequency

counter

to

the

pi

lot ampl

itude

ad-

7.

Adjust

R-3,

the

Modulation

Level

control

for 100%

justment

control.

Adjust

the

frequency

(if r'!eces-

subcarrier

modulation.

11/73

-15-

dropouts

of

carrier.

8.

Reduce

the

input

signal

level

by

40

dB

and

adjust

the

Mute

level

control

R-9, whi Ie

observing

the

waveform

at

the

output

of

Q-7

unti I

the

wave

form

peaks

just

start

to

cl ip.

This

will

prevent

noise

from

holding

the

SeA

carrier

on

and

wi

II

avoid

unwanted

9.

Remove

the

audio

input

signal

and

observe

the

time

delay

for

the

carrier

to

squelch.

Adjust

R-M,

the

mute

delay

potentiometer

for

the

desired

delay

per-

iod.

·16·

VII. STAN0 AR0 PR

E-E

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.

i I

'::

,

~..;::

:+

-

...

......

." I

r!

··I

f!-;

,::

.

11'

.

~

W

.'

.t

t

1-. ,

~

·

-

I

n mHh i'

iJ

..

. .Y;i:

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;;p.

'

U

tt

.

~WI-U

W

m!tt!

~t.

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1

fi

~

'Ii

t

·;

f-

:.

2

ff

H.

~

7:

l

~

ori•

..

·1

-2-

-

')

-oJ

·4

·

so

It

1

..

+·

:

10c

--

.

...

-

I

';

.

..

II

•' .

.,

I'

...

. t

,-

::1 .

...

"

.~

!=J;

200 400 600

to

Hertz

~~

LI .

'

,1-

'

.-

,

2000

~

I

1

"-

,I

.

..

I.

tll"

~

;t:.

..

:

~

:

fF:

_

"J.!

,I

'I

~

-.4

~

::

.t:

t ·

t·

...

·

..

IT

~

"

i:!

•••

I

..

.

~

i

!:

·

-t

,I

1..

.lI

.-

~

Ff

m

" l

ttlliWfijOO.

'

1i

4000

6000

10.000

15,000

11/73

VIII.

FCC

STANDARDS

BROADCAST

(FCC R&

R,

Section 73.317, Nov., 1972)

MODULATION

...............................

± 75

kHz

=

100%

AUDIO

FREQUENCY

REQUIREMENTS

.............

...........

..

...

..

50

-15,000

Hz

PRE·

EMPHASIS

75

microseconds

OJRVE

....

..

...

......

..

.......

.

..

. .

.....

.

TOTAL

HARMONIC

DISTORTION

FOR

25%,

SO%

and

111m!.

.......

...

..

.

...........

50·100

Hz

3.5%

100·7500

Hz

2.5%

7500

-15,000

Hz

3.0%

The transmitter should not produce over

Y2

of

the above

maximum

distortion figures.

FM

SIN

..............

..

Greater

than

60

dB

below

100%

FM

(SO

Hz·l5kHz) Modulation

AM

SIN

..........

..

Greater

than

50

dB below

100%

AM

(SO

Hz.15kHz)

Modulation

CARRIER

FREQUENCY

DEVIATION.

..

.. ..

. . . .. . . . . .

....

......

...

.

..

•..

±

2000

Hz

All

unwanted emissions must

be

43

+

10

Log (Power

in

Watts) below the carrier power.

STEREO

PILOT FREQUENCy

...................•....

19,000

Hz,

± 2

Hz

PILOT INJECTION

..........

.

.......

"

.....

..........

8 -

10%

[8)0

®lJ

(Q)I·

STEREO

SUB

CARRIER

SUPPRESSION

LESS

THAN

1%

MODULATION

..................

..

.

...

..

1%

= -

40

dB

SUB

CARRIER

FREQUENCY

RESPONSE

.

..

.

......

.

...

.

.. ..

50 -15,000

Hz

MAXIMUM

L - R

MODUU

TION

..

......

..

.

...

•. . .

.....

.. . . . .

.•

...

45%

of

total

MAXIMUM

L +R

(MAIN

CHANNEL)

...........

.

...

. ..

..

.....

.

...

....

45%

of total

STEREO

SEPARATION

Left

into

Right...

.

...

..

.

..

. . .

..

.

..

. . . . 29.7 dB minimum

Right into

L.ft

.

.. ..

..

• .

....

.

.....

. .

..

...

29.7 dB minimum

(FOR

ALL

FREQUENCIES

BETWEEN

50

AND

15,000

Hz)

Cross talk:

Main

into Subchannel,

or

Subchannel into

Main

shall

be

greater than

40

dB

below

90%

modula-

tion.

When

monaural

main

channel programming is used, the

SCA

carrier must

be

between 20-74

kHz.

Total

of

all

SCA

subcarriets shall

not

exceed

30%

modulation

of

carrier.

If

engaged

in

stereo, the

SCA

carrier frequency

shall

be

between

53

to

75

kHz.

Total

of

subcarriers

shall not exceed

10%

modulation

of

the

main

carrier.

Crosstalk

of

the

SCA

subcarrier into the

main

channel

shall

be

greater than

60

dB

below

100%

modulation

for

the frequency range

of

50

-15,000

Hz.

IX.

PARTS

LIST

The majority

of

the components used are

of

standard

valuesand

tolerances generally available

from

local ele.

ctronics jobbers. Those components

of

unusual tolerances

or

of

McMartin

Manufacture are listed here.

11/73

SYMBOL

R-7,

8,

10

R-9

C-2,

7,

11

C-5,8

C-l0

Q-l,

2,

3

Q-4

SW·l

T-l

FL·l

MODULE

II

1,

MONAURAL

AUDIO

CARD

PIN DESCRIPTION

540001

10K

ohm,

1%,

metal film

resistor

540019 3010

ohm,

1%,

metal

film

resistor

670002 3.3

mf,

35V,

10%

tantalum capacitor

600027

20

mf,

16V,

electrolytic capacitor

600019 1000

mf,

16V,

electrolytic capacitor

201050 SE-4010 transistor

201056 2N3569 transistor

480004 Single pole, double

throw

switch

910046 600

ohm

cud

io

transformer

15

kHz

low

pass filter

-17

-

-18-

SYMBOL

R-7,

8,

BA,

26,

27,

28A

R-9,

28

R-20

R-21

C-2,

8,

12,

16,22,26

C-6,

20

C-14

C-l3,

27

Gl-l,

2,

3,

5.

6,

7

Q-4,8

SW-l

T-l,

2

FL-l, 2

MODULE

II

1,

STEREO

AUDIO

(OPTIONAL)

540001

540019

400059

400041

670002

660015

600019

600009

201050

201056

480026

910046

DESCRIPTION

10K

ohm,

1%,

Y2w

metal

film

resistor

3010

ohm,

1%,

Y2W

metal

film

resistor

250

ohm,

trim

pot

1K

ohm,

trim

pot

3.3

mf,

35V,

10%

tantalum capacitor

5.5 -

18

pf,

variable capacitor

1000

mf,

16V,

electrolytic capacitor

160

mf,

25V,

electrolytic capacitor

SE-4010

tra

ns

istor

2N3569 trans istor

Double pole, double throw switch

600

ohm,

audio transformer

15

kHz

low

pass filter

MODULE

II

2,

STEREO

GENERATOR

(OPTIONAL)

SYMBOL

PiN DESCRIPTION

R-2,

31

400053 2.5K

ohm,

trim

pot

R-4,

5

540001

10K

ohm,

1%,

Y2W

metal

film

resistor

R-6,

9

540021

4750

ohm,

1%,

Y2W

metal

film

resistor

R-11,

12,20,24

400050 250

ohm,

trim

pot

R-46

401012

5K

ohm,

pot

R-47

401017

lOOK

ohm,

pot

C-3,

4,

5 670005 220

mf,

10V,

tantalum capacitor

C-7 600019 1000

mf,

16V,

electrolytic cappcitor

C-11

660026 5-25

pf,

variable capacitor

C-15 670004 2.2

mf,

20V,

tantalum capacitor

C-18

670011

3.9

mf,

35V,

10%

tantalum capacitor

C-20,

22

116049 6800

pf,

33V,

polystyrene capacitor

C-21

116104 12000

pf,

33V,

polystyrene capacitor

SW-l

480004 Single Pole,

doubl'e

throw

switch

D-l

210008

IN-4006

rectifier diode

RL

Y-l

470027 5000

ohm

relay

Q-l,2

201088 2N709 transistor

Q-3,

4,

6,

7,

8 201050 SE-4010 transistor

Gl-5

201056 2N3569 transistor

IC-l

230041

MC7473P

integrated circuit

L-l, 2

932041

12.0mh

pot

core inductor

Xtal-l 090018

76

kHz

crystal

Z-l 220007

13V

SIR

13B

Zener diode

MODULE

II 2or

3,

SeA

GENERATOR

(OPTIONAL)

SYMBOL

DESCRIPTION

R-3

400041

1K

ohm,

trim

pot

R-9

400053 2.5K

ohm,

trim

pot

R-l0 400055

10K

ohm,

trim

pot

R-11

402006 250

ohm,

Pot

R-16,20 540017 68380

ohm,

1%,

Y2

Wmetal

film

resistor

11173

McMartin B-910 User manual

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