<s>
A	O
tuner	B-Device
is	O
a	O
subsystem	O
that	O
receives	O
radio	O
frequency	O
(	O
RF	O
)	O
transmissions	O
,	O
such	O
as	O
FM	B-Application
broadcasting	O
,	O
and	O
converts	O
the	O
selected	O
carrier	O
frequency	O
and	O
its	O
associated	O
bandwidth	B-Algorithm
into	O
a	O
fixed	O
frequency	O
that	O
is	O
suitable	O
for	O
further	O
processing	O
,	O
usually	O
because	O
a	O
lower	O
frequency	O
is	O
used	O
on	O
the	O
output	O
.	O
</s>
<s>
Broadcast	O
FM/AM	O
transmissions	O
usually	O
feed	O
this	O
intermediate	O
frequency	O
(	O
IF	O
)	O
directly	O
into	O
a	O
demodulator	B-Device
that	O
converts	O
the	O
radio	O
signal	O
into	O
audio-frequency	O
signals	O
that	O
can	O
be	O
fed	O
into	O
an	O
amplifier	O
to	O
drive	O
a	O
loudspeaker	O
.	O
</s>
<s>
More	O
complex	O
transmissions	O
like	O
PAL/NTSC	O
(	O
TV	O
)	O
,	O
DAB	O
(	O
digital	O
radio	O
)	O
,	O
DVB-T/DVB-S/DVB	O
-C	O
(	O
digital	B-Application
TV	I-Application
)	O
etc	O
.	O
</s>
<s>
use	O
a	O
wider	O
frequency	B-Algorithm
bandwidth	I-Algorithm
,	O
often	O
with	O
several	O
subcarriers	O
.	O
</s>
<s>
These	O
are	O
transmitted	O
inside	O
the	O
receiver	B-Device
as	O
an	O
intermediate	O
frequency	O
(	O
IF	O
)	O
.	O
</s>
<s>
Subcarriers	O
are	O
then	O
processed	O
like	O
real	O
radio	O
transmissions	O
,	O
but	O
the	O
whole	O
bandwidth	B-Algorithm
is	O
sampled	O
with	O
an	O
analog-to-digital	O
converter	O
(	O
A/D	O
)	O
at	O
a	O
rate	O
faster	O
than	O
the	O
Nyquist	O
rate	O
(	O
that	O
is	O
,	O
at	O
least	O
twice	O
the	O
IF	O
frequency	O
)	O
.	O
</s>
<s>
A	O
tuner	B-Device
can	O
also	O
refer	O
to	O
a	O
radio	O
receiver	B-Device
or	O
standalone	O
audio	O
component	O
that	O
is	O
part	O
of	O
an	O
audio	O
system	O
such	O
as	O
a	O
hi-fi	O
or	O
stereo	O
,	O
to	O
be	O
connected	O
to	O
a	O
separate	O
amplifier	O
.	O
</s>
<s>
The	O
verb	O
tuning	O
in	O
radio	O
contexts	O
means	O
adjusting	O
the	O
receiver	B-Device
to	O
detect	O
the	O
desired	O
radio	O
signal	O
carrier	O
frequency	O
that	O
a	O
particular	O
radio	O
station	O
uses	O
.	O
</s>
<s>
The	O
simplest	O
tuner	B-Device
consists	O
of	O
an	O
inductor	O
and	O
capacitor	O
connected	O
in	O
parallel	O
,	O
where	O
the	O
capacitor	O
or	O
inductor	O
is	O
made	O
to	O
be	O
variable	O
.	O
</s>
<s>
Combined	O
with	O
a	O
detector	B-Algorithm
,	O
also	O
known	O
as	O
a	O
demodulator	B-Device
(	O
diode	O
D1	O
in	O
the	O
circuit	O
)	O
,	O
it	O
becomes	O
the	O
simplest	O
radio	O
receiver	B-Device
,	O
often	O
called	O
a	O
crystal	O
set	O
.	O
</s>
<s>
Often	O
several	O
sections	O
would	O
be	O
provided	O
on	O
a	O
tuning	O
capacitor	O
,	O
to	O
tune	O
several	O
stages	O
of	O
the	O
receiver	B-Device
in	O
tandem	O
,	O
or	O
to	O
allow	O
switching	O
between	O
different	O
frequency	O
bands	O
.	O
</s>
<s>
A	O
later	O
method	O
used	O
a	O
potentiometer	B-Device
supplying	O
a	O
variable	O
voltage	O
to	O
varactor	O
diodes	O
in	O
the	O
local	O
oscillator	O
and	O
tank	O
circuits	O
of	O
front	O
end	O
tuner	B-Device
,	O
for	O
electronic	O
tuning	O
.	O
</s>
<s>
Modern	O
radio	B-Device
tuners	I-Device
use	O
a	O
superheterodyne	O
receiver	B-Device
with	O
tuning	O
selected	O
by	O
adjustment	O
of	O
the	O
frequency	O
of	O
a	O
local	O
oscillator	O
.	O
</s>
<s>
Still	O
later	O
,	O
phase	O
locked	O
loop	O
methods	O
were	O
used	O
,	O
with	O
microprocessor	B-Architecture
control	O
.	O
</s>
<s>
In	O
a	O
self-contained	O
radio	O
receiver	B-Device
for	O
audio	O
,	O
the	O
signal	O
from	O
the	O
detector	B-Algorithm
after	O
the	O
tuner	B-Device
is	O
run	O
through	O
a	O
volume	O
control	O
and	O
to	O
an	O
amplifier	O
stage	O
.	O
</s>
<s>
In	O
a	O
tuner	B-Device
component	O
of	O
an	O
audio	O
system	O
(	O
for	O
example	O
,	O
a	O
home	O
high-fidelity	O
system	O
or	O
a	O
public	O
address	O
system	O
in	O
a	O
building	O
)	O
,	O
the	O
output	O
of	O
the	O
detector	B-Algorithm
is	O
connected	O
to	O
a	O
separate	O
external	O
system	O
of	O
amplifiers	O
and	O
speakers	O
.	O
</s>
<s>
The	O
broadcast	O
audio	O
FM	B-Application
band	O
(	O
in	O
most	O
countries	O
)	O
is	O
around	O
higher	O
in	O
frequency	O
than	O
the	O
AM	B-Device
band	O
and	O
provides	O
enough	O
space	O
for	O
a	O
bandwidth	B-Algorithm
of	O
This	O
bandwidth	B-Algorithm
is	O
sufficient	O
to	O
transmit	O
both	O
stereo	O
channels	O
with	O
almost	O
the	O
full	O
hearing	O
range	O
.	O
</s>
<s>
The	O
left	O
and	O
right	O
audio	O
signals	O
must	O
be	O
combined	O
into	O
a	O
single	O
signal	O
which	O
is	O
applied	O
to	O
the	O
modulation	O
input	O
of	O
the	O
transmitter	O
;	O
this	O
is	O
done	O
by	O
the	O
addition	O
of	O
an	O
inaudible	O
subcarrier	O
signal	O
to	O
the	O
FM	B-Application
broadcast	O
signal	O
.	O
</s>
<s>
FM	B-Application
stereo	O
allows	O
left	O
and	O
right	O
channels	O
to	O
be	O
transmitted	O
.	O
</s>
<s>
The	O
availability	O
of	O
FM	B-Application
stereo	O
,	O
a	O
quieter	O
VHF	B-Algorithm
broadcast	O
band	O
,	O
and	O
better	O
fidelity	O
led	O
to	O
the	O
specialization	O
of	O
FM	B-Application
broadcasting	O
in	O
music	O
,	O
tending	O
to	O
leave	O
AM	B-Device
broadcasting	O
with	O
spoken-word	O
material	O
.	O
</s>
<s>
Standalone	O
audio	O
stereo	O
FM	B-Device
tuners	I-Device
are	O
sought	O
after	O
for	O
audiophile	O
and	O
TV/FM	O
DX	O
applications	O
,	O
especially	O
those	O
produced	O
in	O
the	O
1970s	O
and	O
early	O
1980s	O
,	O
when	O
performance	O
and	O
manufacturing	O
standards	O
were	O
among	O
the	O
highest	O
.	O
</s>
<s>
In	O
many	O
instances	O
the	O
tuner	B-Device
may	O
be	O
modified	O
to	O
improve	O
performance	O
.	O
</s>
<s>
Electronics	O
specialists	O
and	O
hobbyists	O
buy	O
,	O
collect	O
and	O
restore	O
vintage	O
FM	B-Application
or	O
AM/FM	O
audio	O
tuners	B-Device
on	O
the	O
secondary	O
market	O
.	O
</s>
<s>
The	O
tuner	B-Device
is	O
outfitted	O
with	O
improved	O
tolerance	O
and	O
better	O
sounding	O
upgraded	O
parts	O
.	O
</s>
<s>
Prices	O
have	O
increased	O
relative	O
to	O
the	O
increasing	O
demand	O
for	O
the	O
older	O
audio	O
tuners	B-Device
.	O
</s>
<s>
Most	O
of	O
the	O
early	O
tuner	B-Device
models	O
were	O
designed	O
and	O
manufactured	O
to	O
receive	O
only	O
the	O
AM	B-Device
broadcast	O
band	O
.	O
</s>
<s>
As	O
FM	B-Application
became	O
more	O
popular	O
,	O
the	O
limitations	O
of	O
AM	B-Device
became	O
more	O
apparent	O
,	O
and	O
FM	B-Application
became	O
the	O
primary	O
listening	O
focus	O
,	O
especially	O
for	O
stereo	O
and	O
music	O
broadcasting	O
.	O
</s>
<s>
The	O
McIntosh	O
MR78	O
is	O
known	O
as	O
one	O
of	O
the	O
first	O
FM	B-Device
tuners	I-Device
precise	O
enough	O
to	O
tune	O
into	O
a	O
weaker	O
station	O
broadcast	O
on	O
the	O
same	O
frequency	O
as	O
another	O
stronger	O
signal	O
.	O
</s>
<s>
In	O
Europe	O
,	O
where	O
a	O
second	O
AM	B-Device
broadcast	O
band	O
is	O
used	O
for	O
longwave	B-Algorithm
broadcasting	I-Algorithm
,	O
tuners	B-Device
may	O
be	O
fitted	O
with	O
both	O
the	O
standard	O
medium	O
wave	O
and	O
the	O
additional	O
longwave	B-Algorithm
band	O
.	O
</s>
<s>
However	O
,	O
radios	O
with	O
only	O
medium	O
wave	O
are	O
also	O
common	O
,	O
especially	O
in	O
countries	O
where	O
there	O
are	O
no	O
longwave	B-Algorithm
broadcasters	O
.	O
</s>
<s>
Rarely	O
,	O
radios	O
are	O
sold	O
with	O
only	O
FM	B-Application
and	O
longwave	B-Algorithm
,	O
but	O
no	O
medium	O
wave	O
band	O
.	O
</s>
<s>
Some	O
tuners	B-Device
may	O
also	O
be	O
equipped	O
with	O
one	O
or	O
more	O
short	O
wave	O
bands	O
.	O
</s>
<s>
A	O
television	B-Device
tuner	I-Device
converts	O
a	O
radio	O
frequency	O
analog	O
television	O
or	O
digital	B-Application
television	I-Application
transmission	O
into	O
audio	O
and	O
video	O
signals	O
which	O
can	O
be	O
further	O
processed	O
to	O
produce	O
sound	O
and	O
a	O
picture	O
.	O
</s>
<s>
Different	O
tuners	B-Device
are	O
used	O
for	O
different	O
television	O
standards	O
such	O
as	O
PAL	B-Language
,	O
NTSC	O
,	O
ATSC	B-Device
,	O
SECAM	O
,	O
DVB-C	B-Device
,	O
DVB-T	O
,	O
DVB-T2	B-Protocol
,	O
ISDB	B-Protocol
,	O
T-DMB	O
,	O
open	O
cable	O
.	O
</s>
<s>
Television	O
channel	O
frequencies	O
were	O
non-contiguous	O
,	O
with	O
many	O
non-broadcast	O
services	O
interleaved	O
between	O
VHF	B-Algorithm
channels	O
6	O
and	O
7	O
in	O
North	O
America	O
,	O
for	O
example	O
.	O
</s>
<s>
Instead	O
,	O
TV	B-Device
tuners	I-Device
of	O
the	O
era	O
incorporated	O
multiple	O
sets	O
of	O
tuned	O
circuits	O
for	O
the	O
main	O
signal	O
path	O
and	O
local	O
oscillator	O
circuit	O
.	O
</s>
<s>
These	O
"	O
turret	O
"	O
tuners	B-Device
mechanically	O
switched	O
the	O
receiving	O
circuits	O
by	O
rotating	O
a	O
knob	O
to	O
select	O
the	O
desired	O
channel	O
.	O
</s>
<s>
When	O
UHF	O
TV	O
broadcasting	O
was	O
made	O
available	O
,	O
often	O
two	O
complete	O
separate	O
tuner	B-Device
stages	O
were	O
used	O
,	O
with	O
separate	O
tuning	O
knobs	O
for	O
selection	O
of	O
VHF	B-Algorithm
band	I-Algorithm
and	O
UHF	O
band	O
channels	O
.	O
</s>
<s>
To	O
allow	O
for	O
a	O
small	O
amount	O
of	O
drift	O
or	O
misalignment	O
of	O
the	O
tuner	B-Device
with	O
the	O
actual	O
transmitted	O
frequency	O
,	O
tuners	B-Device
of	O
that	O
era	O
included	O
a	O
"	O
fine	O
tuning	O
"	O
knob	O
to	O
allow	O
minor	O
adjustment	O
for	O
best	O
reception	O
.	O
</s>
<s>
The	O
combination	O
of	O
high	O
frequencies	O
,	O
multiple	O
electrical	O
contacts	O
,	O
and	O
frequent	O
changing	O
of	O
channels	O
in	O
the	O
tuner	B-Device
made	O
it	O
a	O
high	O
maintenance	O
part	O
of	O
the	O
television	O
receiver	B-Device
,	O
as	O
relatively	O
small	O
electrical	O
or	O
mechanical	O
problems	O
with	O
the	O
tuner	B-Device
would	O
make	O
the	O
set	O
unusable	O
.	O
</s>
<s>
Analog	O
tuners	B-Device
can	O
tune	O
only	O
analog	O
signals	O
.	O
</s>
<s>
An	O
ATSC	B-Device
tuner	I-Device
is	O
a	O
digital	B-Device
tuner	I-Device
that	O
tunes	O
digital	O
signals	O
only	O
.	O
</s>
<s>
Some	O
digital	B-Device
tuners	I-Device
provide	O
an	O
analog	O
bypass	O
.	O
</s>
<s>
VHF/UHF	O
TV	B-Device
tuners	I-Device
are	O
rarely	O
found	O
as	O
a	O
separate	O
component	O
,	O
but	O
are	O
incorporated	O
into	O
television	O
sets	O
.	O
</s>
<s>
Cable	O
boxes	O
and	O
other	O
set	O
top	O
boxes	O
contain	O
tuners	B-Device
for	O
digital	B-Application
TV	I-Application
services	O
,	O
and	O
send	O
their	O
output	O
via	O
SCART	B-Protocol
or	O
other	O
connector	O
,	O
or	O
using	O
an	O
RF	O
modulator	O
(	O
typically	O
on	O
in	O
Europe	O
and	O
in	O
North	O
America	O
)	O
to	O
TV	O
receivers	B-Device
that	O
do	O
not	O
natively	O
support	O
the	O
services	O
.	O
</s>
<s>
Many	O
can	O
be	O
used	O
with	O
video	O
monitors	O
that	O
do	O
not	O
have	O
a	O
TV	B-Device
tuner	I-Device
or	O
direct	O
video	O
input	O
.	O
</s>
<s>
They	O
are	O
often	O
part	O
of	O
a	O
VCR	O
or	O
digital	B-Application
video	I-Application
recorder	I-Application
(	O
DVR	O
,	O
PVR	O
)	O
.	O
</s>
<s>
Personal	B-Device
computers	I-Device
may	O
be	O
fitted	O
with	O
expansion	B-Device
cards	I-Device
(	O
typically	O
with	O
PCI	B-Protocol
or	O
USB	B-Protocol
interface	O
)	O
providing	O
a	O
TV	B-Device
tuner	I-Device
and	O
digital	B-Architecture
signal	I-Architecture
processor	I-Architecture
(	O
DSP	O
)	O
.	O
</s>
<s>
They	O
may	O
be	O
dedicated	O
TV	B-Device
tuner	I-Device
cards	I-Device
,	O
or	O
incorporated	O
into	O
a	O
video	B-Device
card	I-Device
.	O
</s>
<s>
Many	O
earlier	O
models	O
were	O
stand-alone	O
tuners	B-Device
,	O
designed	O
only	O
to	O
deliver	O
TV	O
pictures	O
through	O
a	O
VGA	B-Protocol
connector	I-Protocol
;	O
this	O
allowed	O
viewing	O
television	O
on	O
a	O
computer	O
display	O
,	O
but	O
did	O
not	O
support	O
recording	O
television	O
programs	O
.	O
</s>
<s>
Smartphone	B-Application
and	O
tablets	B-Device
can	O
use	O
a	O
Micro	O
USB	B-Protocol
DVB-T	O
receiver	B-Device
to	O
watch	O
DVB-T	O
TV	O
.	O
</s>
<s>
An	O
electronic	O
tuner	B-Device
is	O
a	O
device	O
which	O
tunes	O
across	O
a	O
part	O
of	O
the	O
radio	O
frequency	O
spectrum	O
by	O
the	O
application	O
of	O
a	O
voltage	O
or	O
appropriate	O
digital	O
code	O
words	O
.	O
</s>
<s>
This	O
type	O
of	O
tuner	B-Device
supersedes	O
mechanical	O
tuners	B-Device
,	O
which	O
were	O
tuned	O
by	O
manual	O
adjustment	O
of	O
capacitance	O
or	O
inductance	O
in	O
the	O
tuned	O
circuits	O
.	O
</s>
<s>
In	O
a	O
more	O
practical	O
and	O
everyday	O
sense	O
,	O
a	O
radio	O
or	O
television	O
set	O
which	O
is	O
tuned	O
by	O
manually	O
turning	O
a	O
knob	O
or	O
dial	O
contains	O
a	O
manual	O
tuner	B-Device
into	O
which	O
the	O
shaft	O
of	O
that	O
knob	O
or	O
dial	O
extends	O
.	O
</s>
<s>
The	O
electronic	O
button	O
rack	O
controlling	O
the	O
new	O
electronic	O
varactor	O
tuner	B-Device
was	O
popular	O
in	O
television	O
sets	O
of	O
the	O
1970s	O
and	O
1980s	O
.	O
</s>
<s>
Modern	O
electronic	O
tuners	B-Device
also	O
use	O
varactor	O
diodes	O
as	O
the	O
actual	O
tuning	O
elements	O
,	O
but	O
the	O
voltages	O
which	O
change	O
their	O
capacitance	O
are	O
obtained	O
from	O
a	O
digital-to-analog	O
converter	O
(	O
DAC	O
)	O
driven	O
by	O
a	O
microprocessor	B-Architecture
or	O
phase	O
locked	O
loop	O
(	O
PLL	O
)	O
arrangement	O
.	O
</s>
