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REAR PANEL CONNECTIONS
1. ANTENNATERMINALS.
This receiver
is equipped
with
four
antenna
terminals; each
is a
threaded
metal
shaft
with
a plastic
thumbscrew and
a
toothed washer which
will
make secure
contact
either
with
bare
wire
or with the
U-shaped metal
spade
lug
that
is
often
provided on antenna
wires.
lf
you are
using an antenna
whose
lead-in
wires
have
some
other
type of connector,
cut
it off and strip off enough
insulation
to expose
approximately
1
cm
(1/z
inch)
ol
bare
wire
on each conductor.
To
connect
the antenna wire,
unscrew the
appropriate
thumbscrew, place
the spade
lug
or
bare
wire
under
the
toothed washer, and turn the
thumb-
screw clockwise until
it
is
tight.
The
toothed
washer
will
grip
the
lug or
wire, making
a
connection that
is
secure
both
electrically and
mechanicallY.
AM.
Some
form of
external antenna
will
be needed
for satislactory
reception,
since the
7'120
does
not have
a
built-in AM antenna.
For
most
local broadcasting
stations
a
simple
wire
up
to one meter
(three
feet)
in length
will
provide
ample
signal strength,
and such a
single-wire antenna
is
included with
the
receiver. Connect one end
ol
the wire to
the
AM
terminal. The
remainder
ol
the
antenna
may
be
allowed to
hang
down
behind
the
receiver
or
may be tacked
in
place horizontally
along
the
rear
of
a
wooden-not
metal-shell.
(A metal
shelf
may interfere
with
reception;
in
that
case
the
wire
should
be
stretched
out along the wall
away
lrom the shelving
and
tacked
in
place.)
You
may wish
to experiment
with
the orientation of
the
AM
antenna,
in
order
to
find the
position
that
provides
the
best reception
of the stations you
listen
to
most often.
The short-wire antenna
usually
will
provide
satisfactory
reception
ol
local
AM
broadcast
stations
But if you wish to
improve reception
of
distant
AM
stations, attach
a long-wire
outdoor
antenna
to the
AM
terminal. As
its name
implies,
a
"long-wire" antenna
is a simple, straight
wire whose
length
may be anything
from
a
few feet
up to about
100
leet
(30
meters), mounted
parallel to
the earth
and as high as
is
convenient.
ln some cases
the
effectiveness
of
a long-wire
antenna
will
be
improved
by
connecting
a second wire
from
the Ground
(G)
terminal to
a
true earth-ground,
i'e.
a
copper-plated
rod
driven
several
feet
into
the
earth.
A
substitute electrical ground
may also prove effective:
a
cold-water pipe,
a
steam
radiator,
or
the
third
hole
of
a modern
electrical wall
socket.
FM.
Some
form
of external
antenna must
be connected
to
the receiver for effective
reception of
stereo
FM broad-
casts. A ribbon-wire "folded dipole" antenna
is supplied with
the receiver to
get
you started.
When
you stretch
out the
ribbon-wire antenna
you
will
note
that
it is
in
the form
of
a
"T". The "crossbar" portion of the Tshould
be
stretched
out
horizontally
and
tacked
in
place-on
a
wall,
on
the
back
of
a
cabinet,
or on the floor.
The "vertical"
section
of
the
T
goes
to
the receiver's antenna terminals.
Connect its two
wires
to
the
two
3000
inPut
terminals.
ln view
of the
excellent
sensitivity of this
receiver,
you
may find
that the
ribbon-wire
dipole antenna
is all you
need
for reception
of
strong
local
stations.
But it is not
very
efficient
at rejecting "multipath"
and other
forms of
FM
interference, and
it cannot
easily
be rotated to
optimize
its
pickup
pattern
for best
reception
of stations
in different
directions. Therefore,
in most cases you
should
use a better
antenna.
The
recommended
options,
in
order of
increasing
cost, are
as follows:
(1)
Abasic
"rabbit-ears"
indoor
TVantenna without
auxiliary coils or tuning switches.
Electrically, such
an
antenna
is
just another dipole
(similar to
the
ribbon-wire
antenna) with
its
tuned elements
made
of solid
metal, but
with
the
advantage
that
it
can
be rotated. Stretch out each
of
its
two
arms
to
a length of
30 inches
(75 cm), and
orient
them horizontally or
at
a
shallow
angle
upward
(less than
45
degrees). The ribbon-wire
emerging
from
the antenna's
base
should
be
connected
to
the receiver's two
300O termi-
nals
in
place
oI the ribbon-wire
antenna supplied with the
receiver.
Now for
each
station
in
turn, after
you tune the
station you can
rotate the
antenna for
best reception.
(2)
A
more
elaborate rabbit-ears
indoor
TV
antenna
with
a
tuning
switch. This type
of
antenna
does
NOT have
greater
sensitivity
than
the simpler rabbit-ears
unit,
so
iI
your problem
is
that the
signals you want
to
receive are
weak and
noisy,
then
an
outdoor antenna
is
the only effec-
tive solution.
But in
cities and
in large buildings where
signals
are
strong
but are
contaminated
by reflected
"mul-
tipath"
signats
that interfere
with
good
reception, the tuning
switch on
an
elaborate
indoor
antenna
may
improve
recep-
tion by
reducing
the
interference.
(3)
An
electrically tuned indoor
antenna,
such
as the
Technics
Wing or B.l.C.
Beam Box.
Again, such
antennas
usually
do
not provide any advantage
over the simplest
type
of "rabbit-ears"
unit
for
receiving weak
signals.
But
where
a
strong signal
is
contaminated
by
interference,lhe
antenna's
aiming
and
tuning controls can
reject
the interference
and
yield cleaner
reception.
(4)
An
outdoor antenna,
Even the
finest
indoor an-
tenna,
no
matter
how elaborate, cannot
fully
exploit the
capabilities of
a
good
FM tuner. For
the lowest
noise,
minimum
distortion, and
largest choice of
well-received
broadcasts,
an
outdoor antenna
is
the
best complement
to
a
fine
tuner.
A roof-mounted antenna
has three
fundamental
advan-
tages.
First,
its large
size
yields
better
sensitivity
(pulling
in
a
stronger
signal
from
the
desired station) and
a narrower
directional
pattern
for
more effective rejection
of
multipath
reflections
arriving
from other directions. Second,
its loca-
tion
on
a rool or tall
mast
places
it
above
many sources of
interference-other
buildings,
passing
cars and
buses, etc.
Third, the strength of received
FM signals is
directly
propor-
tional
to
the height of the antenna
above
the
ground.
lf
you already
have an
outdoor television antenna,
using
a
splitter
to
extract
FM signals
from
it may produce excellent
results.
However, many
TV
antennas
are
deliberately
de-
signed to
be relatively
weak at
FM
frequencies
in
order
to
minimize potential interference
with TV
signals
at nearby
frequencies (Channel
6 in
the
U.S.).
You
may be able
to
use
a
splitter to extract
FM signals
from
an
apartment
building's
master
TV
antenna system,
but usually
this yields
poor
results
because
many
master antenna
systems
have
"traps" to stop
FM signals.
The
best
choice
is a
directional
FM-only antenna,
mounted
as high above
ground
as is
practical,
and sepa-
rated
by
at
least
two meters
(7
feet)
from
other
antennas,
vertically and
horizontally. A
shielded
lead-in cable
will
be
mandatory
in
most locations,
both
to minimize interlerence
and
to preserve strong
signals
during
years of weathering.
The cable
may be either
75-ohm
coaxial
or
a shielded
300-ohm type.
ll
desired stations are
located in different
directions
(more
than
90
degrees apart),
a rotor
will
also
be
needed
in
order to
aim
the
antenna.
lf
you are
using a
75-ohm
coaxial
cable
(either
lrom
your outdoor antenna
or
from
a master
antenna
system),
connect
it as
follows.
First remove any
connector that
may
have
been
fitted.
Strip off about an inch (2 cm)
of the
outer
insulation to
expose
the
shield
wiring, fold
back the shield
and
twist
its
wire
strands together, then
strip
off a half-inch
(1
cm) of insulation
from
the center
conductor. Disconnect
any antenna connected to
the 300O
terminals.
Connect the
coixial
cable's center conductor
to
the
75O
terminal
and
connect the coaxial cable's
shield wire
to
the adjacent
ground (G)terminal.
After you
have
completed
all
of the
antenna connec-
tions,
examine
them to
be sure
that
adjacent
wires
or
connectors are
not
touching
each other,
short-circuiting
the
antenna
signal.
2.
PHONO INPUT. This
input
is
designed for
use with
phono
cartridges of the moving magnet,
induced magnet,
moving
flux, and moving iron
(variable reluctance) types,
and
wiifr "high-output" moving-coil pickups
(i.e., those with
a
rated
output
of
1.0
mVor
greater).
The
input impedance
at
the
Phono
jacks
is 47K
ohms in
parallel
with
100 pE
3
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