Harman Kardon ST350 Owners Manual - Page 6

5.

FM

selects

the

FM

band

for

monophonic

reception.

6.

FM

-AFC

selects

the

FM

band

for

monophonic

reception

with

the

addi-

tion

of

a

powerful

Automatic

Frequency

Control

circuit

to

help

retune

the

sta-

tion

by

a

tuning

ratio

of

10:1.

7.

POWER

OFF

when

depressed

turns

the

tuner

off.

To

turn

the

tuner

on

merely

depress

any

other

push

button.

Automatic

Frequency

Control:

FM

Broadcasting,

by

its

very

nature,

eliminates

almost

all

natural

and

man-

made

static.

However,

the

characteristics

of

FM

which

makes

this

possible

also

causes

specific

problems

in

tuning.

The

Madrigal,

Model

ST350

incorporates

a

special

electronic

circuit

known

as

AFC

(Automatic

Frequency

Control)

that

overcomes

these

problems

and

insures

proper

tuning

even

if

the

manual

tuning

is

not

accurately

done.

Therefore

AFC

always

keeps

the

station

in

the

center

of

the

channel

and

eliminates

distortion

caused

by

inaccurate

tuning.

It

should

be

pointed

out

that

AFC

is

not

a

means

to

eliminate

tuner

drift.

A

fi

ne

piece

of

electronic

equipment

as

the

ST350

will

not

drift

on

any

FM

push

button

position

whether

on

FM

or

FM

-AFC.

The

following

experiment

will

lead

to

an

understanding

of

AFC,

and

the

fuller

enjoyment

of

the

ST350

tuner.

Tune

across

the

FM

band

with

the

push

button

selector

switch

in

the

FM

-

AFC

position.

Note

how

the

stations

"pop"

into

place.

Now

tune

to

any

station,

preferably

one

with

a

musical

program.

Defeat

the

AFC

circuit

by

depressing

the

FM

pushbutton,

and

tune

slowly

through

the

station

from

left

to

right.

Notice

there

are

three

distinct

points

where

the

station

sounds

clear,

interspersed

with

points

of

distorted

sound.

The

middle

clear

-sounding

point

is

the

proper

tuning

position

for

the

best

tone

quality

with

minimum

noise

and

interference.

Detune

the

station

so

that

the

sound

is

distorted.

Now

depress

the

FM

-AFC

push

button

and

notice

how

the

sounds

clear

up.

The

tuning

has

been

readjusted

by

the

operation

of

the

AFC

circuit,

which

automatically

retunes

the

electronic

circuits

to

the

center

of

the

station

channel.

In

order

to

take

advantage

of

the

benefits

of

AFC,

it

is

suggested

that

fi

ne

tuning

be

done

with

the

push

button

selector

in

the

FM

position.

When

the

push

button

selector

is

then

depressed

to

the

FM

-AFC

position

the

automatic

fre-

quency

control

circuit

will

improve

your

careful

tuning

by

a

tuning

factor

of

10:1.

The

procedure

is

especially

recommended

when

a

weak

station

is

being

tuned

on

a

channel

adjacent

to

a

stronger

one.

This

will

prevent

the

AFC

from

reaching

for

the

more

powerful

signal

thereby

skipping

over

the

weaker

one.

Whenever

a

weak

station

is

tuned,

the

AFC

circuit

should

be

defeated.

ADJUSTMENTS

In

some

installations,

hum

may

be

encountered

due

to

a

voltage

difference

between

the

amplifier,

tuner

and

record

player

chassis.

This

may

be

eliminated

by

reversing

one

or

all

of

the

AC

power

cords.

Simply

reverse

one

at

a

time

until

improvement

is

experienced.

It

is

recommended

to

test

the

tubes

of

this

tuner

approximately

every

twelve

months.

When

a

tube

is

changed

it

may

be

necessary

to

have

the

tuner

realigned

to

insure

optimum

performance.

Harman Kardon ST350 Owners Manual - Page 6

Automatic, Frequency, Control, ADJUSTMENTS

Page 6 highlights