<s>
The	O
radio	B-Algorithm
spectrum	I-Algorithm
is	O
the	O
part	O
of	O
the	O
electromagnetic	O
spectrum	O
with	O
frequencies	O
from	O
3Hz	O
to	O
3,000	O
GHz	O
(	O
3THz	O
)	O
.	O
</s>
<s>
Different	O
parts	O
of	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
are	O
allocated	O
by	O
the	O
ITU	O
for	O
different	O
radio	O
transmission	O
technologies	O
and	O
applications	O
;	O
some	O
40	O
radiocommunication	O
services	O
are	O
defined	O
in	O
the	O
ITU	O
's	O
Radio	O
Regulations	O
(	O
RR	O
)	O
.	O
</s>
<s>
In	O
some	O
cases	O
,	O
parts	O
of	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
are	O
sold	O
or	O
licensed	O
to	O
operators	O
of	O
private	O
radio	O
transmission	O
services	O
(	O
for	O
example	O
,	O
cellular	O
telephone	O
operators	O
or	O
broadcast	O
television	O
stations	O
)	O
.	O
</s>
<s>
Because	O
it	O
is	O
a	B-Algorithm
fixed	O
resource	O
which	O
is	O
in	O
demand	O
by	O
an	O
increasing	O
number	O
of	O
users	O
,	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
has	O
become	O
increasingly	O
congested	O
in	O
recent	O
decades	O
,	O
and	O
the	O
need	O
to	O
utilize	O
it	O
more	O
effectively	O
is	O
driving	O
modern	O
telecommunications	O
innovations	O
such	O
as	O
trunked	O
radio	O
systems	O
,	O
spread	B-Architecture
spectrum	I-Architecture
,	O
ultra-wideband	O
,	O
frequency	O
reuse	O
,	O
dynamic	O
spectrum	B-Algorithm
management	I-Algorithm
,	O
frequency	O
pooling	O
,	O
and	O
cognitive	B-Protocol
radio	I-Protocol
.	O
</s>
<s>
The	O
frequency	O
boundaries	O
of	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
are	O
a	B-Algorithm
matter	O
of	O
convention	O
in	O
physics	O
and	O
are	O
somewhat	O
arbitrary	O
.	O
</s>
<s>
At	O
the	O
high	B-Algorithm
frequency	I-Algorithm
end	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
is	O
bounded	O
by	O
the	O
infrared	O
band	O
.	O
</s>
<s>
The	O
terahertz	B-Architecture
band	I-Architecture
,	O
from	O
300gigahertz	O
to	O
3terahertz	O
,	O
can	O
be	O
considered	O
either	O
as	O
microwaves	O
or	O
infrared	O
.	O
</s>
<s>
Because	O
it	O
is	O
a	B-Algorithm
fixed	O
resource	O
,	O
the	O
practical	O
limits	O
and	O
basic	O
physical	O
considerations	O
of	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
,	O
the	O
frequencies	O
which	O
are	O
useful	O
for	O
radio	O
communication	O
,	O
are	O
determined	O
by	O
technological	O
limitations	O
which	O
are	O
impossible	O
to	O
overcome	O
.	O
</s>
<s>
So	O
although	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
is	O
becoming	O
increasingly	O
congested	O
,	O
there	O
is	O
no	O
possible	O
way	O
to	O
add	O
additional	O
frequency	B-Algorithm
bandwidth	I-Algorithm
outside	O
of	O
that	O
currently	O
in	O
use	O
.	O
</s>
<s>
Below	O
about	O
10kHz	O
(	O
a	B-Algorithm
wavelength	O
of	O
30km	O
)	O
,	O
elevated	O
wire	O
antennas	O
kilometers	O
in	O
diameter	O
are	O
required	O
,	O
so	O
very	O
few	O
radio	O
systems	O
use	O
frequencies	O
below	O
this	O
.	O
</s>
<s>
A	B-Algorithm
second	O
limit	O
is	O
the	O
decreasing	O
bandwidth	B-Algorithm
available	O
at	O
low	B-Algorithm
frequencies	I-Algorithm
,	O
which	O
limits	O
the	O
data	O
rate	O
that	O
can	O
be	O
transmitted	O
.	O
</s>
<s>
The	O
lowest	O
frequencies	O
that	O
have	O
been	O
used	O
for	O
radio	O
communication	O
are	O
around	O
80Hz	O
,	O
in	O
ELF	B-Language
submarine	O
communications	O
systems	O
built	O
by	O
a	B-Algorithm
few	O
nations	O
 '	O
navies	O
to	O
communicate	O
with	O
their	O
submerged	O
submarines	O
hundreds	O
of	O
meters	O
underwater	O
.	O
</s>
<s>
These	O
employ	O
huge	O
ground	O
dipole	O
antennas	O
20	O
–	O
60km	O
long	O
excited	O
by	O
megawatts	O
of	O
transmitter	O
power	O
,	O
and	O
transmit	O
data	O
at	O
an	O
extremely	O
slow	O
rate	O
of	O
about	O
1	B-Language
bit	O
per	O
minute	O
(	O
17	O
millibits	O
per	O
second	O
,	O
or	O
about	O
5	B-Algorithm
minutes	O
per	O
character	O
)	O
.	O
</s>
<s>
As	O
frequency	O
increases	O
above	O
30GHz	O
(	O
the	O
beginning	O
of	O
the	O
millimeter	O
wave	O
band	O
)	O
,	O
atmospheric	O
gases	O
absorb	O
increasing	O
amounts	O
of	O
power	O
,	O
so	O
the	O
power	O
in	O
a	B-Algorithm
beam	O
of	O
radio	O
waves	O
decreases	O
exponentially	O
with	O
distance	O
from	O
the	O
transmitting	O
antenna	O
.	O
</s>
<s>
At	O
30GHz	O
,	O
useful	O
communication	O
is	O
limited	O
to	O
about	O
1	B-Language
km	O
,	O
but	O
as	O
frequency	O
increases	O
the	O
range	O
at	O
which	O
the	O
waves	O
can	O
be	O
received	O
decreases	O
.	O
</s>
<s>
In	O
the	O
terahertz	B-Architecture
band	I-Architecture
above	O
300GHz	O
,	O
the	O
radio	O
waves	O
are	O
attenuated	O
to	O
zero	O
within	O
a	B-Algorithm
few	O
meters	O
,	O
so	O
the	O
atmosphere	O
is	O
essentially	O
opaque	O
.	O
</s>
<s>
A	B-Algorithm
radio	B-Algorithm
band	I-Algorithm
is	O
a	B-Algorithm
small	O
contiguous	O
section	O
of	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
frequencies	O
,	O
in	O
which	O
channels	O
are	O
usually	O
used	O
or	O
set	O
aside	O
for	O
the	O
same	O
purpose	O
.	O
</s>
<s>
To	O
prevent	O
interference	O
and	O
allow	O
for	O
efficient	O
use	O
of	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
,	O
similar	O
services	O
are	O
allocated	O
in	O
bands	O
.	O
</s>
<s>
For	O
each	O
of	O
these	O
bands	O
the	O
ITU	O
has	O
a	B-Algorithm
bandplan	B-Algorithm
which	O
dictates	O
how	O
it	O
is	O
to	O
be	O
used	O
and	O
shared	O
,	O
to	O
avoid	O
interference	O
and	O
to	O
set	O
protocol	O
for	O
the	O
compatibility	O
of	O
transmitters	O
and	O
receivers	O
.	O
</s>
<s>
As	O
a	B-Algorithm
matter	O
of	O
convention	O
,	O
the	O
ITU	O
divides	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
into	O
12	B-Architecture
bands	O
,	O
each	O
beginning	O
at	O
a	B-Algorithm
wavelength	O
which	O
is	O
a	B-Algorithm
power	O
of	O
ten	O
(	O
10n	O
)	O
metres	O
,	O
with	O
corresponding	O
frequency	O
of	O
3×108−nhertz	O
,	O
and	O
each	O
covering	O
a	B-Algorithm
decade	O
of	O
frequency	O
or	O
wavelength	O
.	O
</s>
<s>
Each	O
of	O
these	O
bands	O
has	O
a	B-Algorithm
traditional	O
name	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
term	O
high	B-Algorithm
frequency	I-Algorithm
(	O
HF	B-Algorithm
)	O
designates	O
the	O
wavelength	O
range	O
from	O
100	O
to	O
10metres	O
,	O
corresponding	O
to	O
a	B-Algorithm
frequency	O
range	O
of	O
3	B-Algorithm
to	O
30MHz	O
.	O
</s>
<s>
This	O
is	O
just	O
a	B-Algorithm
symbol	O
and	O
is	O
not	O
related	O
to	O
allocation	O
;	O
the	O
ITU	O
further	O
divides	O
each	O
band	O
into	O
subbands	O
allocated	O
to	O
different	O
services	O
.	O
</s>
<s>
Above	O
300GHz	O
,	O
the	O
absorption	O
of	O
electromagnetic	O
radiation	O
by	O
Earth	O
's	O
atmosphere	O
is	O
so	O
great	O
that	O
the	O
atmosphere	O
is	O
effectively	O
opaque	O
,	O
until	O
it	O
becomes	O
transparent	O
again	O
in	O
the	O
near-infrared	O
and	O
optical	O
window	O
frequency	O
ranges	O
.	O
</s>
<s>
These	O
ITU	O
radio	B-Algorithm
bands	I-Algorithm
are	O
defined	O
in	O
the	O
ITU	O
Radio	O
Regulations	O
.	O
</s>
<s>
Article2	O
,	O
provision	O
No.2.1	O
states	O
that	O
"	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
shall	O
be	O
subdivided	O
into	O
nine	O
frequency	O
bands	O
,	O
which	O
shall	O
be	O
designated	O
by	O
progressive	O
whole	O
numbers	O
in	O
accordance	O
with	O
the	O
following	O
table	O
"	O
.	O
</s>
<s>
The	O
table	O
originated	O
with	O
a	B-Algorithm
recommendation	O
of	O
the	O
fourth	O
CCIR	O
meeting	O
,	O
held	O
in	O
Bucharest	O
in	O
1937	O
,	O
and	O
was	O
approved	O
by	O
the	O
International	O
Radio	O
Conference	O
held	O
at	O
Atlantic	O
City	O
,	O
NJ	O
in	O
1947	O
.	O
</s>
<s>
The	O
idea	O
to	O
give	O
each	O
band	O
a	B-Algorithm
number	O
,	O
in	O
which	O
the	O
number	O
is	O
the	O
logarithm	O
of	O
the	O
approximate	O
geometric	O
mean	O
of	O
the	O
upper	O
and	O
lower	O
band	O
limits	O
in	O
Hz	O
,	O
originated	O
with	O
B.C.	O
</s>
<s>
Fleming-Williams	O
,	O
who	O
suggested	O
it	O
in	O
a	B-Algorithm
letter	O
to	O
the	O
editor	O
of	O
Wireless	O
Engineer	O
in	O
1942	O
.	O
</s>
<s>
Band	O
name	O
Abbreviation	O
ITU	O
band	O
number	O
Frequency	O
and	O
wavelength	O
Example	O
uses	O
Extremely	B-Language
low	I-Language
frequency	I-Language
ELF	B-Language
1	B-Language
Communication	O
with	O
submarines	O
Super	B-Algorithm
low	I-Algorithm
frequency	I-Algorithm
SLF	B-Algorithm
2	B-Algorithm
Communication	O
with	O
submarines	O
Ultra	B-Algorithm
low	I-Algorithm
frequency	I-Algorithm
ULF	B-Algorithm
3	B-Algorithm
Communication	O
with	O
submarines	O
,	O
communication	O
within	O
mines	O
,	O
landline	B-Application
telephony	I-Application
,	O
fax	O
machines	O
,	O
fiber-optic	B-Application
communication	I-Application
Very	B-Architecture
low	I-Architecture
frequency	I-Architecture
VLF	B-Architecture
4	B-Architecture
Navigation	O
,	O
time	O
signals	O
,	O
communication	O
with	O
submarines	O
,	O
landline	B-Application
telephony	I-Application
,	O
wireless	O
heart	O
rate	O
monitors	O
,	O
geophysics	O
Low	B-Algorithm
frequency	I-Algorithm
LF	B-Algorithm
5	B-Algorithm
Navigation	O
,	O
time	O
signals	O
,	O
AM	O
longwave	B-Algorithm
broadcasting	O
(	O
Europe	O
and	O
parts	O
of	O
Asia	O
)	O
,	O
RFID	B-Application
,	O
amateur	O
radio	O
.	O
</s>
<s>
Medium	B-Algorithm
frequency	I-Algorithm
MF	B-Algorithm
6	B-Algorithm
AM	O
(	O
medium-wave	B-Algorithm
)	O
broadcasts	O
,	O
amateur	O
radio	O
,	O
avalanche	O
beacons	O
,	O
magnetic	O
resonance	O
imaging	O
,	O
positron	B-Application
emission	I-Application
tomography	I-Application
,	O
electrical	O
telegraph	O
,	O
wireless	O
telegraphy	O
,	O
radioteletype	O
,	O
dial-up	O
internet	O
.	O
</s>
<s>
High	B-Algorithm
frequency	I-Algorithm
HF	B-Algorithm
7	B-Algorithm
Shortwave	O
broadcasts	O
,	O
citizens	B-Application
band	I-Application
radio	I-Application
,	O
amateur	O
radio	O
,	O
over-the-horizon	B-Architecture
aviation	O
communications	O
,	O
RFID	B-Application
,	O
over-the-horizon	B-Architecture
radar	I-Architecture
,	O
automatic	B-Device
link	I-Device
establishment	I-Device
(	O
ALE	O
)	O
/	O
near-vertical	O
incidence	O
skywave	O
(	O
NVIS	O
)	O
radio	O
communications	O
,	O
marine	O
and	O
mobile	O
radio	O
telephony	O
,	O
CT	O
scan	O
,	O
magnetic	O
resonance	O
imaging	O
,	O
positron	B-Application
emission	I-Application
tomography	I-Application
,	O
ultrasound	B-Application
,	O
cordless	O
phones	O
.	O
</s>
<s>
Very	B-Algorithm
high	I-Algorithm
frequency	I-Algorithm
VHF	B-Algorithm
8	B-Algorithm
FM	O
broadcasts	O
,	O
television	O
broadcasts	O
,	O
cable	O
television	O
broadcasting	O
,	O
radars	B-Application
,	O
line-of-sight	O
ground-to-aircraft	B-Application
,	O
aircraft-to-aircraft	O
communications	O
,	O
radioteletype	O
,	O
land	O
mobile	O
and	O
maritime	O
mobile	O
communications	O
,	O
amateur	O
radio	O
,	O
police	O
,	O
fire	O
and	O
emergency	O
medical	O
services	O
scanners	O
,	O
weather	O
radio	O
,	O
CT	O
scan	O
,	O
magnetic	O
resonance	O
imaging	O
,	O
positron	B-Application
emission	I-Application
tomography	I-Application
,	O
ultrasound	B-Application
,	O
cordless	O
phones	O
.	O
</s>
<s>
Ultra	O
high	B-Algorithm
frequency	I-Algorithm
UHF	O
9	O
Television	O
broadcasts	O
,	O
cable	O
television	O
broadcasting	O
,	O
microwave	O
oven	O
,	O
radars	B-Application
,	O
microwave	O
devices/communications	O
,	O
radio	O
astronomy	O
,	O
radars	B-Application
(	O
L	B-Algorithm
band	I-Algorithm
)	O
,	O
mobile	O
phones	O
,	O
wireless	B-Architecture
LAN	I-Architecture
,	O
Bluetooth	B-Protocol
,	O
Zigbee	B-Protocol
,	O
GPS	O
and	O
two-way	O
radios	O
such	O
as	O
land	O
mobile	O
,	O
FRS	O
and	O
GMRS	B-General_Concept
radios	O
,	O
amateur	O
radio	O
,	O
satellite	O
radio	O
,	O
police	O
,	O
fire	O
and	O
emergency	O
medical	O
services	O
scanners	O
,	O
remote	O
control	O
systems	O
,	O
ADSB	B-Application
,	O
cordless	O
phones	O
,	O
internet	O
,	O
dial-up	O
internet	O
,	O
satellite	O
broadcasting	O
,	O
communication	O
satellites	O
,	O
weather	O
satellites	O
,	O
satellite	O
phones	O
(	O
L	B-Algorithm
band	I-Algorithm
)	O
,	O
satellite	O
phones	O
(	O
S	B-Algorithm
band	I-Algorithm
)	O
.	O
</s>
<s>
Super	B-Algorithm
high	I-Algorithm
frequency	I-Algorithm
SHF	B-Algorithm
10	B-Algorithm
Radio	O
astronomy	O
,	O
microwave	O
devices/communications	O
,	O
wireless	B-Architecture
LAN	I-Architecture
,	O
DSRC	O
,	O
most	O
modern	O
radars	B-Application
,	O
communications	O
satellites	O
,	O
cable	O
and	O
satellite	O
television	O
broadcasting	O
,	O
DBS	O
,	O
amateur	O
radio	O
,	O
satellite	O
broadcasting	O
,	O
communication	O
satellites	O
,	O
weather	O
satellites	O
,	O
satellite	O
radio	O
,	O
cordless	O
phones	O
,	O
internet	O
,	O
satellite	O
phones	O
(	O
S	B-Algorithm
band	I-Algorithm
)	O
.	O
</s>
<s>
Extremely	O
high	B-Algorithm
frequency	I-Algorithm
EHF	O
11	O
Radio	O
astronomy	O
,	O
satellite	O
broadcasting	O
,	O
communication	O
satellites	O
,	O
weather	O
satellites	O
,	O
high-frequency	B-Algorithm
microwave	O
radio	O
relay	O
,	O
microwave	O
remote	B-Application
sensing	I-Application
,	O
directed-energy	O
weapon	O
,	O
millimeter	O
wave	O
scanner	O
,	O
Wireless	B-General_Concept
Lan	I-General_Concept
802.11ad	I-General_Concept
,	O
internet	O
.	O
</s>
<s>
The	O
term	O
"	O
tremendously	O
low	B-Algorithm
frequency	I-Algorithm
"	O
(	O
TLF	O
)	O
has	O
been	O
used	O
for	O
wavelengths	O
from	O
0	O
–	O
3Hz	O
(	O
300,000	O
–	O
100,000	O
km	O
)	O
,	O
but	O
the	O
term	O
has	O
not	O
been	O
defined	O
by	O
the	O
ITU	O
.	O
</s>
<s>
This	O
convention	O
began	O
around	O
World	O
War	O
II	O
with	O
military	O
designations	O
for	O
frequencies	O
used	O
in	O
radar	B-Application
,	O
which	O
was	O
the	O
first	O
application	O
of	O
microwaves	O
.	O
</s>
<s>
Unfortunately	O
,	O
there	O
are	O
several	O
incompatible	O
naming	O
systems	O
for	O
microwave	O
bands	O
,	O
and	O
even	O
within	O
a	B-Algorithm
given	O
system	O
the	O
exact	O
frequency	O
range	O
designated	O
by	O
a	B-Algorithm
letter	O
may	O
vary	O
somewhat	O
between	O
different	O
application	O
areas	O
.	O
</s>
<s>
One	O
widely	O
used	O
standard	O
is	O
the	O
IEEE	O
radar	B-Application
bands	O
established	O
by	O
the	O
US	O
Institute	O
of	O
Electrical	O
and	O
Electronics	O
Engineers	O
.	O
</s>
<s>
+	O
Radar-frequency	O
bands	O
according	O
to	O
IEEE	O
standardIEEE	O
Std	O
521-2002	O
Standard	O
Letter	O
Designations	O
for	O
Radar-Frequency	O
Bands	O
.	O
</s>
<s>
Banddesignation	O
Frequency	O
range	O
Explanation	O
of	O
meaning	O
of	O
letters	O
HF	B-Algorithm
0.003	O
to	O
0.03	O
GHz	O
High	B-Algorithm
frequency	I-Algorithm
VHF	B-Algorithm
0.03	O
to	O
0.3	O
GHz	O
Very	B-Algorithm
high	I-Algorithm
frequency	I-Algorithm
UHF	O
0.3	O
to	O
1	B-Language
GHz	O
Ultra-high	O
frequency	O
L	B-Algorithm
1	B-Language
to	O
2	B-Algorithm
GHz	O
Long	B-Algorithm
wave	I-Algorithm
S	B-Algorithm
2	B-Algorithm
to	O
4	B-Architecture
GHz	O
Short	O
wave	O
C	B-Algorithm
4	B-Architecture
to	O
8	B-Algorithm
GHz	O
Compromise	O
between	O
S	B-Algorithm
and	O
X	B-Algorithm
X	B-Algorithm
8	B-Algorithm
to	O
12	B-Architecture
GHz	O
Used	O
in	O
World	O
War	O
II	O
for	O
fire	B-Application
control	I-Application
,	O
X	B-Algorithm
for	O
cross	O
(	O
as	O
in	O
crosshair	O
)	O
.	O
</s>
<s>
NATO	O
LETTER	O
BAND	O
DESIGNATIONNATO	O
Allied	O
Radio	O
Frequency	O
Agency	O
(	O
ARFA	O
)	O
HANDBOOK	O
–	O
VOLUME	O
I	B-Algorithm
;	O
PART	O
IV	O
–	O
APPENDICES	O
,	O
...	O
G-2	O
,	O
...	O
NOMENCLATURE	O
OF	O
THE	O
FREQUENCY	O
AND	O
WAVELENTH	O
BANDS	O
USED	O
IN	O
RADIOCOMMUNCATION	O
.	O
</s>
<s>
Designations	O
for	O
television	O
and	O
FM	O
radio	O
broadcast	O
frequencies	O
vary	O
between	O
countries	O
,	O
see	O
Television	O
channel	O
frequencies	O
and	O
FM	B-Algorithm
broadcast	I-Algorithm
band	I-Algorithm
.	O
</s>
<s>
Since	O
VHF	B-Algorithm
and	O
UHF	O
frequencies	O
are	O
desirable	O
for	O
many	O
uses	O
in	O
urban	O
areas	O
,	O
in	O
North	O
America	O
some	O
parts	O
of	O
the	O
former	O
television	O
broadcasting	O
band	O
have	O
been	O
reassigned	O
to	O
cellular	O
phone	O
and	O
various	O
land	O
mobile	O
communications	O
systems	O
.	O
</s>
<s>
Even	O
within	O
the	O
allocation	O
still	O
dedicated	O
to	O
television	O
,	O
TV-band	B-Algorithm
devices	I-Algorithm
use	O
channels	O
without	O
local	O
broadcasters	O
.	O
</s>
<s>
The	O
Apex	O
band	O
in	O
the	O
United	O
States	O
was	O
a	B-Algorithm
pre-WWII	O
allocation	O
for	O
VHF	B-Algorithm
audio	O
broadcasting	O
;	O
it	O
was	O
made	O
obsolete	O
after	O
the	O
introduction	O
of	O
FM	O
broadcasting	O
.	O
</s>
<s>
Airband	B-Algorithm
refers	O
to	O
VHF	B-Algorithm
frequencies	O
118	O
to	O
137MHz	O
,	O
used	O
for	O
navigation	O
and	O
voice	O
communication	O
with	O
aircraft	O
.	O
</s>
<s>
Trans-oceanic	O
aircraft	O
also	O
carry	O
HF	B-Algorithm
radio	I-Algorithm
and	O
satellite	O
transceivers	O
.	O
</s>
<s>
From	O
the	O
very	O
early	O
days	O
of	O
radio	O
,	O
large	O
oceangoing	O
vessels	O
carried	O
powerful	O
long-wave	B-Algorithm
and	O
medium-wave	B-Algorithm
transmitters	O
.	O
</s>
<s>
High-frequency	B-Algorithm
allocations	O
are	O
still	O
designated	O
for	O
ships	O
,	O
although	O
satellite	O
systems	O
have	O
taken	O
over	O
some	O
of	O
the	O
safety	O
applications	O
previously	O
served	O
by	O
500	O
kHz	O
and	O
other	O
frequencies	O
.	O
</s>
<s>
2182	O
kHz	O
is	O
a	B-Algorithm
medium-wave	B-Algorithm
frequency	O
still	O
used	O
for	O
marine	O
emergency	O
communication	O
.	O
</s>
<s>
Marine	O
VHF	B-Algorithm
radio	O
is	O
used	O
in	O
coastal	O
waters	O
and	O
relatively	O
short-range	O
communication	O
between	O
vessels	O
and	O
to	O
shore	O
stations	O
.	O
</s>
<s>
Amateur	B-Algorithm
radio	I-Algorithm
frequency	I-Algorithm
allocations	I-Algorithm
vary	O
around	O
the	O
world	O
.	O
</s>
<s>
Several	O
bands	O
are	O
common	O
for	O
amateurs	O
worldwide	O
,	O
usually	O
in	O
the	O
HF	B-Algorithm
part	O
of	O
the	O
spectrum	O
.	O
</s>
<s>
Other	O
bands	O
are	O
national	O
or	O
regional	O
allocations	O
only	O
due	O
to	O
differing	O
allocations	O
for	O
other	O
services	O
,	O
especially	O
in	O
the	O
VHF	B-Algorithm
and	O
UHF	O
parts	O
of	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
.	O
</s>
<s>
Citizens	B-Application
 '	I-Application
band	I-Application
radio	I-Application
is	O
allocated	O
in	O
many	O
countries	O
,	O
using	O
channelized	O
radios	O
in	O
the	O
upper	O
HF	B-Algorithm
part	O
of	O
the	O
spectrum	O
(	O
around	O
27MHz	O
)	O
.	O
</s>
<s>
Other	O
frequency	B-Algorithm
allocations	I-Algorithm
are	O
used	O
for	O
similar	O
services	O
in	O
different	O
jurisdictions	O
,	O
for	O
example	O
UHF	B-Algorithm
CB	I-Algorithm
is	O
allocated	O
in	O
Australia	O
.	O
</s>
<s>
A	B-Algorithm
wide	O
range	O
of	O
personal	B-Application
radio	I-Application
services	I-Application
exist	O
around	O
the	O
world	O
,	O
usually	O
emphasizing	O
short-range	O
communication	O
between	O
individuals	O
or	O
for	O
small	O
businesses	O
,	O
simplified	O
license	O
requirements	O
or	O
in	O
some	O
countries	O
covered	O
by	O
a	B-Algorithm
class	O
license	O
,	O
and	O
usually	O
FM	O
transceivers	O
using	O
around	O
1	B-Language
watt	O
or	O
less	O
.	O
</s>
<s>
The	O
ISM	B-Algorithm
bands	I-Algorithm
were	O
initially	O
reserved	O
for	O
non-communications	O
uses	O
of	O
RF	O
energy	O
,	O
such	O
as	O
microwave	O
ovens	O
,	O
radio-frequency	O
heating	O
,	O
and	O
similar	O
purposes	O
.	O
</s>
<s>
However	O
,	O
in	O
recent	O
years	O
the	O
largest	O
use	O
of	O
these	O
bands	O
has	O
been	O
by	O
short-range	O
low-power	O
communications	O
systems	O
,	O
since	O
users	O
do	O
not	O
have	O
to	O
hold	O
a	B-Algorithm
radio	O
operator	O
's	O
license	O
.	O
</s>
<s>
Cordless	O
telephones	O
,	O
wireless	O
computer	O
networks	O
,	O
Bluetooth	B-Protocol
devices	O
,	O
and	O
garage	O
door	O
openers	O
all	O
use	O
the	O
ISM	B-Algorithm
bands	I-Algorithm
.	O
</s>
<s>
Bands	B-Algorithm
of	I-Algorithm
frequencies	I-Algorithm
,	O
especially	O
in	O
the	O
VHF	B-Algorithm
and	O
UHF	O
parts	O
of	O
the	O
spectrum	O
,	O
are	O
allocated	O
for	O
communication	O
between	O
fixed	O
base	O
stations	O
and	O
land	O
mobile	O
vehicle-mounted	O
or	O
portable	B-Application
transceivers	O
.	O
</s>
<s>
In	O
the	O
United	O
States	O
these	O
services	O
are	O
informally	O
known	O
as	O
business	B-Algorithm
band	I-Algorithm
radio	O
.	O
</s>
<s>
Police	O
radio	O
and	O
other	O
public	O
safety	O
services	O
such	O
as	O
fire	O
departments	O
and	O
ambulances	O
are	O
generally	O
found	O
in	O
the	O
VHF	B-Algorithm
and	O
UHF	O
parts	O
of	O
the	O
spectrum	O
.	O
</s>
<s>
The	O
demand	O
for	O
mobile	O
telephone	O
service	O
has	O
led	O
to	O
large	O
blocks	O
of	O
radio	B-Algorithm
spectrum	I-Algorithm
allocated	O
to	O
cellular	B-Protocol
frequencies	I-Protocol
.	O
</s>
<s>
Radio-controlled	O
toys	O
may	O
use	O
portions	O
of	O
unlicensed	B-Algorithm
spectrum	I-Algorithm
in	O
the	O
27MHz	O
or	O
49MHz	O
bands	O
,	O
but	O
more	O
costly	O
aircraft	O
,	O
boat	O
,	O
or	O
land	O
vehicle	O
models	O
use	O
dedicated	O
radio	O
control	O
frequencies	O
near	O
72MHz	O
to	O
avoid	O
interference	O
by	O
unlicensed	O
uses	O
.	O
</s>
<s>
The	O
21st	O
century	O
has	O
seen	O
a	B-Algorithm
move	O
to	O
2.4	B-Algorithm
GHz	I-Algorithm
spread	B-Architecture
spectrum	I-Architecture
RC	O
control	O
systems	O
.	O
</s>
<s>
Licensed	O
amateur	O
radio	O
operators	O
use	O
portions	O
of	O
the	O
6-meter	B-Algorithm
band	I-Algorithm
in	O
North	O
America	O
.	O
</s>
<s>
Radar	B-Application
applications	O
use	O
relatively	O
high	O
power	O
pulse	O
transmitters	O
and	O
sensitive	O
receivers	O
,	O
so	O
radar	B-Application
is	O
operated	O
on	O
bands	O
not	O
used	O
for	O
other	O
purposes	O
.	O
</s>
<s>
Most	O
radar	B-Application
bands	O
are	O
in	O
the	O
microwave	O
part	O
of	O
the	O
spectrum	O
,	O
although	O
certain	O
important	O
applications	O
for	O
meteorology	O
make	O
use	O
of	O
powerful	O
transmitters	O
in	O
the	O
UHF	O
band	O
.	O
</s>
