<s>
A	O
digital	B-Device
channel	I-Device
election	I-Device
was	O
the	O
process	O
by	O
which	O
television	O
stations	O
in	O
the	O
United	O
States	O
chose	O
which	O
physical	O
radio-frequency	O
TV	O
channel	O
they	O
would	O
permanently	O
use	O
after	O
the	O
analog	O
shutdown	O
in	O
2009	O
.	O
</s>
<s>
Stations	O
could	O
choose	O
to	O
keep	O
their	O
initial	O
digital	B-Application
TV	I-Application
channel	O
allocation	O
,	O
do	O
a	O
flash-cut	O
to	O
their	O
former	O
analog	O
TV	O
channel	O
,	O
or	O
attempt	O
to	O
select	O
another	O
channel	O
,	O
often	O
an	O
analog	O
channel	O
or	O
pre-transition	O
digital	O
channel	O
from	O
another	O
station	O
that	O
had	O
been	O
orphaned	O
.	O
</s>
<s>
Stations	O
on	O
channels	O
52	O
to	O
69	O
did	O
not	O
have	O
the	O
first	O
option	O
,	O
as	O
the	O
FCC	O
and	O
then	O
the	O
U.S.	O
Congress	O
revoked	O
them	O
from	O
the	O
bandplan	B-Algorithm
.	O
</s>
<s>
In	O
some	O
cases	O
where	O
the	O
station	O
's	O
current	O
analog	O
tower	O
could	O
not	O
handle	O
the	O
stress	O
of	O
the	O
new	O
digital	O
antenna	O
's	O
weight	O
and	O
wind	O
load	O
,	O
station	O
owners	O
had	O
to	O
construct	O
entirely	O
new	O
broadcast	B-Operating_System
towers	O
in	O
order	O
to	O
comply	O
with	O
the	O
FCC	O
's	O
DTV	O
mandate	O
.	O
</s>
<s>
Most	O
broadcasters	O
were	O
bitter	O
at	O
having	O
to	O
purchase	O
digital	O
equipment	O
and	O
broadcast	B-Operating_System
a	O
digital	O
signal	O
when	O
very	O
few	O
homeowners	O
had	O
digital	B-Application
television	I-Application
sets	O
.	O
</s>
<s>
Aside	O
from	O
the	O
practical	O
considerations	O
above	O
,	O
there	O
are	O
also	O
technical	O
considerations	O
which	O
are	O
based	O
on	O
the	O
physics	O
of	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
.	O
</s>
<s>
The	O
low	O
VHF	B-Algorithm
channels	O
from	O
2	O
to	O
6	O
,	O
while	O
requiring	O
the	O
lowest	O
power	O
(	O
up	O
to	O
100kW	O
analog	O
video	O
or	O
20kW	O
digital	O
)	O
,	O
are	O
prone	O
to	O
electromagnetic	O
interference	O
.	O
</s>
<s>
The	O
ATSC	B-Device
digital	B-Application
TV	I-Application
system	O
has	O
severe	O
problems	O
with	O
susceptibility	O
to	O
impulse	O
noise	O
,	O
bursts	O
of	O
interference	O
which	O
briefly	O
render	O
the	O
entire	O
channel	O
unusable	O
,	O
due	O
to	O
its	O
inability	O
to	O
instantaneously	O
determine	O
where	O
in	O
a	O
video	O
frame	O
to	O
resume	O
display	O
when	O
the	O
signal	O
returns	O
.	O
</s>
<s>
The	O
result	O
is	O
macroblocking	O
and	O
pixelation	B-Algorithm
of	O
the	O
entire	O
signal	O
whenever	O
impulse	O
noise	O
sources	O
(	O
such	O
as	O
motors	O
,	O
appliances	O
or	O
electrical	O
storms	O
)	O
are	O
active	O
.	O
</s>
<s>
Because	O
of	O
the	O
antenna	O
size	O
(	O
a	O
properly-sized	O
VHF	B-Algorithm
TV	O
2	O
dipole	O
spans	O
approximately	O
eight	O
feet	O
(	O
2.7	O
meters	O
)	O
)	O
and	O
the	O
fact	O
that	O
there	O
are	O
only	O
five	O
channels	O
in	O
this	O
band	O
,	O
most	O
set-top	O
antennas	O
are	O
designed	O
to	O
receive	O
the	O
higher	O
TV	O
bands	O
.	O
</s>
<s>
Furthermore	O
,	O
channel	O
6	O
abuts	O
the	O
FM	B-Algorithm
broadcast	I-Algorithm
band	I-Algorithm
at	O
88MHz	O
,	O
possibly	O
causing	O
and	O
receiving	O
interference	O
from	O
adjacent	O
channels	O
.	O
</s>
<s>
(	O
The	O
FCC	O
refused	O
to	O
remove	O
this	O
band	O
from	O
the	O
bandplan	B-Algorithm
,	O
because	O
taking	O
the	O
high	O
UHF	O
channels	O
instead	O
would	O
bring	O
in	O
more	O
money	O
at	O
auction	O
.	O
</s>
<s>
This	O
also	O
contradicts	O
what	O
has	O
been	O
done	O
in	O
every	O
other	O
country	O
that	O
has	O
forced	O
a	O
DTV	O
transition	O
,	O
all	O
giving	O
up	O
the	O
VHF	B-Algorithm
bands	I-Algorithm
.	O
)	O
</s>
<s>
A	O
completely	O
unaddressed	O
issue	O
is	O
the	O
use	O
of	O
HD	O
Radio	O
on	O
88.1	O
FM	O
,	O
where	O
the	O
lower	O
sideband	O
overlaps	O
the	O
far	O
upper	O
sideband	O
of	O
digital	B-Application
TV	I-Application
channel	O
6	O
.	O
</s>
<s>
The	O
upper	O
VHF	B-Algorithm
(	O
band	B-Algorithm
III	I-Algorithm
)	O
,	O
including	O
channels	O
7	O
to	O
13	O
,	O
is	O
better	O
about	O
the	O
above	O
problems	O
,	O
but	O
still	O
not	O
as	O
good	O
as	O
the	O
UHF	O
band	O
.	O
</s>
<s>
By	O
keeping	O
these	O
for	O
TV	O
,	O
it	O
also	O
prevents	O
the	O
use	O
of	O
the	O
band	O
for	O
Digital	O
Audio	O
Broadcasting	B-Operating_System
,	O
as	O
is	O
done	O
with	O
local	O
radio	O
stations	O
in	O
Europe	O
.	O
</s>
<s>
The	O
UHF	O
band	O
contains	O
55	O
channels	O
from	O
14	O
to	O
69	O
,	O
which	O
excludes	O
channel	O
37	O
in	O
the	O
U.S.Channels	O
52	O
to	O
69	O
are	O
unavailable	O
for	O
digital	B-Application
TV	I-Application
,	O
on	O
a	O
permanent	O
basis	O
,	O
leaving	O
only	O
37	O
channels	O
.	O
</s>
<s>
Still	O
,	O
the	O
UHF	O
band	O
has	O
great	O
advantages	O
over	O
VHF	B-Algorithm
,	O
in	O
large	O
part	O
because	O
of	O
its	O
propagation	O
characteristics	O
and	O
lack	O
of	O
impulse	O
noise	O
.	O
</s>
<s>
The	O
shorter	O
wavelength	O
also	O
means	O
that	O
smaller	O
antennas	O
are	O
needed	O
,	O
an	O
advantage	O
for	O
both	O
the	O
broadcaster	B-Operating_System
and	O
the	O
viewer	O
.	O
</s>
<s>
Channel	O
elections	O
generally	O
will	O
not	O
affect	O
consumers	O
in	O
the	O
long	O
run	O
,	O
because	O
virtual	B-Protocol
channel	I-Protocol
numbering	O
will	O
keep	O
stations	O
appearing	O
on	O
their	O
original	O
analog	O
channel	O
numbers	O
,	O
except	O
the	O
times	O
that	O
a	O
station	O
has	O
trouble	O
transmitting	O
PSIP	B-Device
metadata	O
.	O
</s>
<s>
However	O
,	O
most	O
ATSC	B-Device
tuners	I-Device
must	O
re-scan	O
for	O
stations	O
that	O
change	O
their	O
RF	O
channel	O
.	O
</s>
<s>
On	O
some	O
,	O
this	O
is	O
as	O
simple	O
as	O
manually	O
punching	O
in	O
the	O
new	O
RF	O
channel	O
,	O
at	O
which	O
point	O
the	O
decoder	O
will	O
read	O
the	O
PSIP	B-Device
data	O
and	O
re-map	O
to	O
the	O
proper	O
channel	O
number	O
.	O
</s>
<s>
Where	O
stations	O
are	O
moving	O
to	O
a	O
different	O
frequency	O
band	O
(	O
such	O
as	O
UHF	O
to	O
VHF	B-Algorithm
)	O
,	O
this	O
will	O
affect	O
antenna	O
selection	O
.	O
</s>
<s>
Many	O
antennas	O
marketed	O
for	O
HDTV	B-Device
use	O
are	O
UHF-only	O
or	O
perform	O
poorly	O
on	O
VHF	B-Algorithm
,	O
while	O
many	O
82-channel	O
VHF/UHF	O
antennas	O
are	O
a	O
compromise	O
design	O
strongly	O
favoring	O
VHF	B-Algorithm
channels	O
.	O
</s>
