McMartin B-910 Manuale utente

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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

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