Inovonics 705 Manual

Steam Powered Radio.Com

I

/

OPERATING & MAINTENANCE

INSTRUCTION

MANUAL

MODEL

705

'FM/

FMX™

STEREO GENERA

\

Steam Powered Radio.Com

USER'S

RECORD

Model

705

-

Serial

No

......

.

Date

Purchased

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

.

Warranty

Card

Returned?

.

...

.

Purchased

From

.....

.

.......

.

INSTRUCTION

MANUAL

MODEL

705

- I

FM/

FMX™

STEREO

GENERATOR

March,

1988

1305

Fair

Avenue

-

Santa

Cruz,

CA

95060

(408)

458-0552

Steam Powered Radio.Com

I

II

III

IV

V

VI

TABLE

OF

CONTENTS

FUNCTIONAL DESCRIPTION .

Introduction

-

Audio

Pre-Processing

Require-

ments

-

About

FMX™

-

Specifications

-

Block

Diagram

-

Patent

Notice

INSTALLATION

Unpacking

and

Inspection

-

Mounting

-

AC

Power

-

RFI

-

LINE

INPUT

and

Range

Selection

-

Pre-

emphasis

Selection

-COMPOSITE

OUTPUT

and

Impedance

Selection

-

Installation

of

FMX™

3

9

SETUP

AND

OPERATION . . . .

13

Panel

Controls

-

Setup

Procedure

-

Composite

Equalization

Adjustment

CALIBRATION

Equipment

Required

-

Visual

Inspection

-

Strap-

ping

and

Presets

-

Power-Up

-

Input

Gain

-

Highpass

Filter

-

Preemphasis

-

Filter

Tuning

-

Overshoot

Compensation

Adjustment

-

Crosstalk

Trim

-

FMX™

Plug-In

Option

Calibration

-

Final

Level

Setup

CIRCUIT DESCRIPTIONS

.....

.

Input

and

Preemphasis

Stages

-

Filter

Overshoot

Compensator

-

Lowpass

Filter

-

Subcarrier

and

Pilot

Generation

-

Output

Amplifier

-

Power

Supply

-

Plug-In

Option

for

FMX™

. .

17

..

24

APPENDIX . . . . . . . . .

31

Part

Lists

-

Schematics

-

Warranty

PAGE

2

Steam Powered Radio.Com

_

.......

I FUNCTIONAL DESCRIPTION

Introduction

Inovonics'

705

is

a

full-featured

FM

Stereo

Generator

(or

"Stereo

Coder"

in

European

parlance)

which

includes

the

FMX™

"coverage

extension"

transmission

system

as

an

easily-installed

plug-in

option.

FMX™

was

developed

jointly

by

the

Columbia

Broadcasting

System

(CBS)

and

the

U.S.

National

Association

of

Broadcasters

(NAB).

The

system

is

discussed

in

more

detail

at

the

end

of

this

section.

The

705

Generator

incorporates

the

preemphasis

and

lowpass

functions

required

in

customary

broadcasting

practice

and

features

patented

compensation

circuitry

to

avoid

modulation

sacrifices

due

to

filter

overshoots.

FM

subcarrier(s)

and

Pilot

are

digitally

synthesized

for

optimum

and

adjustment-free

operation.

User

adjustments

have,

in

fact,

been

reduced

only

to

those

essential

for

system

matching;

INPUT,

OUTPUT

and

PILOT

levels.

The

one

exception

is

a "COMPOSITE

EQ"

control

which

is

preset

at

the

factory

for

optimum

stereo

separation,

but

which

may

be

readjusted

to

at

least

partially

compensate

for

deficiencies

in

other

parts

of

the

transmission

system.

Audio

Pre-Processing

Requirements

Though

overmodulation

protection

circuitry

is

included

in

the

705,

it

is

anticipated

that

the

Generator

will

be

preceded

by

some

form

of

"audio

processing"

system

which

places

a

ceiling

on

program

peaks

with

specific

allowances

for

"protection"

of

the

preemphasis

characteristic.

It

is

essential

that

this

need

for

"split

spectrum"

audio

processing

be

understood

and

met.

In

FM

broadcasting,

a

high

frequency

preemphasis

(high-end

boost)

characteristic

is

imparted

to

the

input

program

signal

prior

to

transmission.

At

the

receiver

a

complementary

g~~m£hssi~

(high-end

rolloff)

network

restores

overall

flat

frequency

response.

The

purpose

of

this

exercise

is

to

reduce

the

high

frequency

noise

inevitably

added

in

transmission.

This

noise

generally

gets

worse

as

the

listener's

distance

from

the

broadcasting

station

increases.

If

a

low

frequency

tone

(300Hz)

is

applied

to

the

transmitter

input

at

a

level

which

yields

100%

carrier

modulation,

a

high

frequency

tone

(l0kHz)

applied

at

the

same

level

would

over-

~

modulate

the

carrier

(400%

or

more)

because

of

the

preemphasis

curve.

Fortunately,

normal

voice

and

music

program

signals

have

comparatively

low

energy

at

the

higher

frequencies,

and

actual

statistics

of

program

spectral

composition

were

taken

into

PAGE

3

Steam Powered Radio.Com

'-.

account

when

the

preemphasis

characteristic

was

established

years

ago.

Nevertheless,

occasional

high

energy,

high

frequency

peaks

(sibilants,

cymbals,

etc.)

can

still

cause

carrier

overmodu-

lation,

even

when

program

peaks

are

broadband-limited

to

100%-

modulation

values.

This

is

especially

true

when

modern-day

recordings

of

contemporary

music

are

the

program

source.

A

preemphasis

network

ahead

of

a

broadband

limiter,

and

a

deemphasis

circuit

following

it,

will

deal

with

this

situation,

though

the

overall

level

will

"duck"

whenever

a

high-end

peak

occurs.

This

imparts

a

'"choppy··

sound

to

the

program

and

reduces

both

intelligibility

and

perceived

loudness.

What

is

instead

required

is

a

program

limiter

operating

as

a

dual-band

device

with

a

broadband

section

to

cope

with

normal

program

peaks

and

an

inde£endent

high

frequency

limiter

section

(with

proportionally

faster

time

constants)

to

deal

with

those

program

components

subject

to

accentuation

by

the

transmission

preemphasis

characteristic.

A

limiter

of

this

type

(now

common

in

FM

broadcasting

systems)

has

negligible

audible

effect

on

most

program

material,

while

it

provides

absolute

protection

from

carrier

overmodulation.

Overmod

protection

circuitry

within

the

705

takes

the

form

of

a

complex,

active

peak

QliEE~~

integral

with

the

filter

overshoot

compensator.

Because

of

its

unique

mode

of

operation,

a

good

deal

more

peak

clipping

may

be

tolerated

than

with

more

simple

signal

clipping

circuits.

The

705

may,

in

fact,

even

be

used

"barefoot,"

or

with

minimal

audio

pre-processing,

yet

still

yield

quite

acceptable

and

"competitive"

performance.

About

FMX™

is

the

tradename

for

a

patented,

improved

system

of

FM

stereo

broadcasting

which

is

fully

compatible

with

the

customary

standards

and

practices

used

throughout

the

world.

This

means

that

not

only

can

FMX™

transmissions

be

received

by

existing

mono

and

stereo

receivers

with

no

performance

compromises,

but

a

new

generation

of

FMX™-equipped

receivers

can

provide

the

broadcaster

with

a

substantial

increase

in

stereocasting

coverage

(up

to

400%

has

been

claimed

by

the

inventors),

nearly

equalling

the

noise-free

coverage

of

mono

reception.

Development

of

the

Inovonics

705

Stereo

Generator

was

actually

inspired

by

Torick

and

Keller's

1983

invention

of

FMX™

(U.S.

Pat.

4,485,483),

and

the

improvements

it

implied

for

the

entire

FM

broadcasting

industry.

The

Inovonics

Generator

was

designed

from

the

beginning

to

accept

and

support

a

plug-in

circuit

card

for

the

FMX™

system,

leaving

the

"whether"

and

"when"

at

the

option

of

the

individual

broadcaster.

The

FMX™

system

employs

a

second,

"quadrature"

subcarrier

at

the

same

38kHz

as

the

regular

L-R

signal,

but

with

a

90-degree

phase

o££set.

The

additional

subcarrier

is

modulated

by

PAGE

4

Steam Powered Radio.Com

"compressed"

L-R

program

information

which

is

"expanded"

in

the

FMX™

receiver

for

a

much-improved

signal-to-noise

figure.

The

compression

transfer

function

(input

vs.

output)

of

the

"quadrature"

subcarrier

(S')

has

a

"reentrant"

or

dynamic

inversion

characteristic;

that

is,

the

level

of

S'

reaches

a

maximum

value

then

begins

to

drop

(even

as

the

input

continues

to

increase)

until

it

"shuts

off"

completely.

S'

shutoff

is

concurrent

with

maximum

levels

of

the

normal

stereo

subcarrier

(S).

Total

modulation,

including

the

L+R

"mono"

(M)

component,

(M

+ S +

S')

should

never

exceed

the

usual

100%

value

of

the

"interleaved"

stereo

signal.

The

FMX™

compression

function

is

graphed

in

Figure

1.

/

,,

/

-40

/

,,

,

V

-30

Figure

1

i I

8d8

(SPEC)

t_

' V

✓--

-

,-

(~os)l7

/ ,

~

s'

}'

r

I/

\

/.

,,...

V

14d8

~

~v

V s

-20

-10 OdB

INPUT

+10

V

(IOOOi,

MOO.)

\

OdB

-10

-20

-30

-40

+10

0

u

T

p

u

T

FMX™ COMPRESSION CHARACTERISTIC

(S'

compressor

IN

vs.

OUT

relative

to

S)

The

FMX™

receiver

has

a

dual

demodulator

which

independently

recovers

program

information

from

both

the

Sand

S'

subcarriers.

Because

both

signals

are

always

available,

··servo··

techniques

may

be

used

in

the

complementary

expansion

process.

This

obviates

the

perfect

tracking

of

levels

and

time

constants

demanded

by

most

traditional

compander

schemes.

Dematrixed

and

recovered

-~

Left

and

Right

program

channels

are

thus

optimized

for

best

S/N

at

low

levels.

PAGE

5

Steam Powered Radio.Com

The

FMX™

system

is

currently

owned

and

licensed

by

Broadcast

Technology

Partners

(BTP).

It

was

re-engineered

in

1987

to

resolve

certain

technical

issues

which

prevented

universal

acceptance

by

FM

broadcasters

and

receiver

manufacturers

at

the

time

of

first

introduction

in

1986.

The

current

plug-in-option

circuit

card

available

from

Inovonics

contains

all

updates

as

of

the

date

of

manufacture.

Furthermore,

since

FMX™

circuitry

may

be

user-installed

in

a

matter

of

minutes,

any

future

updates

are

very

easily

implemented.

Specifications

Freguenc~

ResEonse

(preemphasis

defeated):

+/-0.5dB,

25Hz-16kHz;

-20dB

or

better

at

lOHz,

-60d8

or

better

at

19kHz

.

Distortion:

<0.1%

THD

in

baseband

and

subcarrier

at

90%

modulation.

NQi~§

(below

100%

modulation,

Pilot

OFF):

-75dB

or

better

in

baseband

and

subcarrier;

38kHz

residual

and

"digital"

noise

above

54kHz,

-60dB

or

better.

Stereo

Separation:

Better

than

55dB,

25Hz-

5kHz;

better

than

50dB,

5kHz-16kHz

.

Crosstalk

(M/S

or

S/M)

:

better

than

-60dB

.

EilQt:

19kHz,

+/-lHz;

<2%

THD

(distortion

products

better

than

55dB

below

100%

modulation);

Pilot

injection

level

adjustable

between

6%

and

12%

relative

to

100%

modulation.

ln~~t~ (LEFT

and

RIGHT) :

Active-balanced,

bridging;

accept

line

input

levels

between

-15dB

and

+15dB

for

100%

modulation.

(OdB = 0 . 775V

r.m

.

s.)

In~ut

Filtering:

7-pole,

phase-corrected,

active-elliptic

"FDNR"

lowpass

with

defeatable

overshoot

compensation

circuitry.

Third-order

Chebyshev

highpass

section.

Preem12hasis:

Selectable

for

75-

or

50-

microsecond

or

"flat

··

transmission

characteristics.

PAGE

6

Steam Powered Radio.Com

-~-

Output:

Single-ended

(unbalanced);

select-

able

75-ohm

or

"zero"

(voltage

source)

impedance.

Level

adjustable

between

-5

and

+12dB

(0.5-3V

r.m.s.

or

1.

2-8V

p-p).

Overmodulation

Protection:

Integral

with

input

filter

overshoot

compensation

circuit

and

defeatable

with

same.

QigiLal

SYnLhesis

Sami;ui~

RaLe:

608kHz

(16X

subcarrier).

O~tion

For

FMX™:

User-installable

auxiliary

plug-in

circuit

board

with

all

parameters

preset.

Power

Requirement:

105-130

or

205-255VAC,

50/60Hz;

8

Watts.

Size

gnd

Y!.§J.gh,t.:

1-3;4··

x

19··

x

8"

(lU);

8

lbs.

Block

Diagram

A

simplified

block

diagram

of

the

705

Stereo

Generator

is

shown

on

Page

8.

Generator

circuitry

is

explained

in

detail

under

Circuit

Descriptions,

Section

V,

which

reference

the

complete

set

of

schematic

diagrams

contained

in

the

Appendix,

Section

VI.

fgt.§nt

Notice

Lowpass

filter

overshoot

compensation

circuitry

employed

in

Inovonics'

Model

705

Stereo

Generator

is

covered

by

U.S.

Patent

No.

4,737,725.

PAGE

7

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Steam Powered Radio.Com

II

INSTALLATION

Unpacking

and

Inspection

Upon

receipt

of

the

equipment,

inspect

carefully

for

shipping

damage.

Should

any

such

damage

be

observed,

notify

the

carrier

at

once;

if

not,

proceed

as

outlined

below.

It

is

recommended

that

the

original

shipping

carton

and

packing

materials

be

saved

should

future

reshipment

become

necessary.

In

the

event

of

return

for

Warranty

repair,

shipping

damage

sustained

as

a

result

of

improper

packing

for

return

may

invalidate

~h~

Warranty.

IT

IS

Y~BY

IMPORTANT

that

the

Warranty

Registration

Card

found

at

the

front

of

this

manual

be

completed

and

returned.

Not

only

does

this

assure

coverage

of

the

equipment

under

terms

of

the

Warranty,

and

pro-

vide

some

means

of

trace

in

the

case

of

lost

or

sto-

len

gear,

but

the

user

will

automatically

receive

specific

SERVICE

OR

MODIFICATION INSTRUCTIONS

should

they

be

issued

by

the

factory.

The

Inovonics

705

is

packaged

to

mount

in

a

standard

19-inch

equipment

rack

and

requires

only

1-3/4

inches

(lU)

of

vertical

rack

space.

The

705

generates

negligible

heat

and,

itself,

is

unaffected

by

wide

variations

in

ambient

operating

temperature.

AC

Power

Unless

specifically

ordered

for

export

shipment,

the

705

is

delivered

for

operation

from

125V,

50/60Hz

AC

mains.

The

back-panel

designation

the

fuseholder

will

confirm

both

the

mains

voltage

selected

and

the

value

of

the

fuse

to

be

used.

Mains

voltage

reselection

is

easily

made

with

the

top

cover

removed.

A

plug-on

jumper

strip

the

power

transformer

may

be

installed

in

either

of

two

positions

for

the

two

nominal

mains

voltages.

A

silkscreened

legend

the

connector

clearly

indicates

its

orientation.

A

proper

fuse

must

always

be

installed,

and

the

appropriate

back-panel

voltage

designation

should

be

marked

to

indicate

the

input

power

requirement.

PAGE

9

Inovonics 705 Manual

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