<s>
In	O
radio	O
,	O
longwave	B-Algorithm
,	O
long	B-Algorithm
wave	I-Algorithm
or	O
long-wave	B-Algorithm
,	O
and	O
commonly	O
abbreviated	O
LW	O
,	O
refers	O
to	O
parts	O
of	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
with	O
wavelengths	O
longer	O
than	O
what	O
was	O
originally	O
called	O
the	O
medium-wave	B-Algorithm
broadcasting	O
band	O
.	O
</s>
<s>
The	O
term	O
is	O
historic	O
,	O
dating	O
from	O
the	O
early	O
20th	O
century	O
,	O
when	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
was	O
considered	O
to	O
consist	O
of	O
longwave	B-Algorithm
(	O
LW	O
)	O
,	O
medium-wave	B-Algorithm
(	O
MW	O
)	O
,	O
and	O
short-wave	O
(	O
SW	O
)	O
radio	B-Algorithm
bands	I-Algorithm
.	O
</s>
<s>
In	O
contemporary	O
usage	O
,	O
the	O
term	O
longwave	B-Algorithm
is	O
not	O
defined	O
precisely	O
,	O
and	O
its	O
intended	O
meaning	O
varies	O
.	O
</s>
<s>
frequencies	O
up	O
to	O
300kilohertz	O
(	O
kHz	O
)	O
,	O
including	O
the	O
International	O
Telecommunication	O
Union	O
's	O
(	O
ITU	O
's	O
)	O
low	B-Algorithm
frequency	I-Algorithm
(	O
LF	O
,	O
30	O
–	O
300kHz	O
)	O
and	O
very	B-Architecture
low	I-Architecture
frequency	I-Architecture
(	O
VLF	B-Architecture
,	O
3	O
–	O
30kHz	O
)	O
bands	O
.	O
</s>
<s>
Sometimes	O
the	O
upper	O
limit	O
is	O
taken	O
to	O
be	O
higher	O
than	O
300kHz	O
,	O
but	O
not	O
above	O
the	O
start	O
of	O
the	O
medium	B-Algorithm
wave	I-Algorithm
broadcast	O
band	O
at	O
520kHz	O
.	O
</s>
<s>
In	O
Europe	O
,	O
Africa	O
,	O
and	O
large	O
parts	O
of	O
Asia	O
(	O
International	O
Telecommunication	O
Union	O
Region	O
1	O
)	O
,	O
where	O
a	O
range	O
of	O
frequencies	O
between	O
148.5	O
and	O
283.5kHz	O
is	O
used	O
for	O
AM	O
broadcasting	O
in	O
addition	O
to	O
the	O
medium-wave	B-Algorithm
band	O
,	O
the	O
term	O
longwave	B-Algorithm
usually	O
refers	O
specifically	O
to	O
this	O
broadcasting	O
band	O
,	O
which	O
falls	O
wholly	O
within	O
the	O
low	B-Algorithm
frequency	I-Algorithm
band	O
of	O
the	O
radio	B-Algorithm
spectrum	I-Algorithm
(	O
30	O
–	O
300kHz	O
)	O
.	O
</s>
<s>
The	O
"	O
Longwave	B-Algorithm
Club	O
of	O
America	O
"	O
(	O
United	O
States	O
)	O
is	O
interested	O
in	O
"	O
frequencies	O
below	O
the	O
AM	O
broadcast	O
band	O
"	O
(	O
i.e.	O
,	O
all	O
frequencies	O
below	O
520kHz	O
)	O
.	O
</s>
<s>
This	O
mode	O
of	O
propagation	O
,	O
called	O
ground	O
wave	O
,	O
is	O
the	O
main	O
mode	O
in	O
the	O
longwave	B-Algorithm
band	O
.	O
</s>
<s>
Low	B-Algorithm
frequency	I-Algorithm
ground	O
waves	O
can	O
be	O
received	O
up	O
to	O
from	O
the	O
transmitting	O
antenna	O
.	O
</s>
<s>
Very	B-Architecture
low	I-Architecture
frequency	I-Architecture
waves	O
below	O
30kHz	O
can	O
be	O
used	O
to	O
communicate	O
at	O
transcontinental	O
distances	O
,	O
and	O
can	O
penetrate	O
saltwater	O
to	O
depths	O
of	O
hundreds	O
of	O
feet	O
,	O
and	O
is	O
used	O
by	O
the	O
military	O
to	O
communicate	O
with	O
submerged	O
submarines	O
.	O
</s>
<s>
Low	B-Algorithm
frequency	I-Algorithm
waves	O
can	O
also	O
occasionally	O
travel	O
long	O
distances	O
by	O
reflecting	O
from	O
the	O
ionosphere	O
(	O
the	O
actual	O
mechanism	O
is	O
one	O
of	O
refraction	O
)	O
,	O
although	O
this	O
method	O
,	O
called	O
skywave	O
or	O
"	O
skip	O
"	O
propagation	O
,	O
is	O
not	O
as	O
common	O
as	O
at	O
higher	O
frequencies	O
.	O
</s>
<s>
Non-directional	O
beacons	O
transmit	O
continuously	O
for	O
the	O
benefit	O
of	O
radio	B-Device
direction	I-Device
finders	I-Device
in	O
marine	O
and	O
aeronautical	O
navigation	O
.	O
</s>
<s>
Radio-controlled	O
clocks	O
receive	O
their	O
time	O
calibration	O
signals	O
with	O
built-in	O
long-wave	B-Algorithm
receivers	O
.	O
</s>
<s>
They	O
use	O
long-wave	B-Algorithm
,	O
rather	O
than	O
short-wave	O
or	O
medium-wave	B-Algorithm
,	O
because	O
long-wave	B-Algorithm
signals	O
from	O
the	O
transmitter	O
to	O
the	O
receiver	O
always	O
travel	O
along	O
the	O
same	O
direct	O
path	O
across	O
the	O
surface	O
of	O
the	O
Earth	O
,	O
so	O
the	O
time	O
delay	O
correction	O
for	O
the	O
signal	O
travel	O
time	O
from	O
the	O
transmitting	O
station	O
to	O
the	O
receiver	O
is	O
always	O
the	O
same	O
for	O
any	O
one	O
receiving	O
location	O
.	O
</s>
<s>
Longwaves	B-Algorithm
travel	O
by	O
groundwaves	O
that	O
hug	O
the	O
surface	O
of	O
the	O
earth	O
,	O
unlike	O
mediumwaves	B-Algorithm
and	O
shortwaves	O
.	O
</s>
<s>
The	O
delay	O
between	O
when	O
the	O
long-wave	B-Algorithm
signal	O
was	O
sent	O
from	O
the	O
transmitter	O
(	O
when	O
the	O
coded	O
time	O
was	O
correct	O
)	O
and	O
when	O
the	O
signal	O
is	O
received	O
by	O
the	O
clock	O
(	O
when	O
the	O
coded	O
time	O
is	O
slightly	O
late	O
)	O
depends	O
on	O
the	O
overland	O
distance	O
between	O
the	O
clock	O
and	O
the	O
transmitter	O
and	O
the	O
speed	O
of	O
light	O
through	O
the	O
air	O
,	O
which	O
is	O
also	O
very	O
nearly	O
constant	O
.	O
</s>
<s>
Since	O
the	O
time	O
lag	O
is	O
essentially	O
the	O
same	O
,	O
a	O
single	O
constant	O
shift	O
forward	O
from	O
the	O
time	O
coded	O
in	O
the	O
signal	O
can	O
compensate	O
for	O
all	O
long-wave	B-Algorithm
signals	O
received	O
at	O
any	O
one	O
location	O
from	O
the	O
same	O
time	O
signal	O
station	O
.	O
</s>
<s>
Nowadays	O
,	O
in	O
the	O
United	O
States	O
,	O
Part	O
15	O
of	O
FCC	O
regulations	O
allow	O
unlicensed	O
use	O
of	O
the	O
160	O
–	O
190kHz	O
band	O
a	O
transmitter	O
/	O
amplifier	O
output	O
power	O
to	O
the	O
antenna	O
of	O
at	O
most	O
1watt	O
,	O
with	O
an	O
antenna	O
at	O
most	O
15meters	O
(	O
49feet	O
)	O
high	O
;	O
this	O
is	O
called	O
Low	B-Algorithm
Frequency	I-Algorithm
Experimental	O
Radio	O
(	O
LowFER	O
)	O
.	O
</s>
<s>
Frequencies	O
from	O
472	O
–	O
479kHz	O
are	O
available	O
to	O
licensed	O
amateurs	O
as	O
the	O
new	O
630	O
m	O
band	O
,	O
part	O
of	O
the	O
now-defunct	O
maritime	O
band	O
,	O
but	O
this	O
is	O
often	O
considered	O
a	O
medium	B-Algorithm
wave	I-Algorithm
sub-band	O
.	O
</s>
<s>
Swedish	O
station	O
SAQ	O
,	O
located	O
at	O
the	O
Varberg	O
Radio	O
Station	O
facility	O
in	O
Grimeton	O
,	O
is	O
the	O
last	O
remaining	O
operational	O
Alexanderson	O
alternator	O
long-wave	B-Algorithm
transmitter	O
.	O
</s>
<s>
Longwave	B-Algorithm
is	O
used	O
for	O
broadcasting	O
only	O
within	O
ITU	O
Region	O
1	O
.	O
</s>
<s>
The	O
long-wave	B-Algorithm
broadcasters	O
are	O
located	O
in	O
western	O
,	O
northern	O
,	O
central	O
,	O
and	O
southeastern	O
Europe	O
,	O
the	O
former	O
Soviet	O
Union	O
,	O
Mongolia	O
,	O
Algeria	O
,	O
and	O
Morocco	O
.	O
</s>
<s>
Typically	O
,	O
a	O
larger	O
geographic	O
area	O
can	O
be	O
covered	O
by	O
a	O
long-wave	B-Algorithm
broadcast	O
transmitter	O
compared	O
to	O
a	O
medium-wave	B-Algorithm
one	O
.	O
</s>
<s>
With	O
the	O
adoption	O
of	O
the	O
Geneva	O
Frequency	O
Plan	O
of	O
1975	O
,	O
long-wave	B-Algorithm
carrier	O
frequencies	O
are	O
exact	O
multiples	O
of	O
9kHz	O
;	O
ranging	O
from	O
153	O
to	O
279kHz	O
.	O
</s>
<s>
One	O
exception	O
was	O
a	O
French-language	O
station	O
,	O
Europe	O
1	O
in	O
Germany	O
,	O
which	O
retained	O
its	O
prior	O
channel	O
spacing	O
until	O
the	O
long-wave	B-Algorithm
service	O
was	O
terminated	O
in	O
2019	O
.	O
</s>
<s>
Until	O
the	O
1970s	O
,	O
some	O
long-wave	B-Algorithm
stations	O
in	O
northern	O
and	O
eastern	O
Europe	O
and	O
the	O
Soviet	O
Union	O
operated	O
on	O
frequencies	O
as	O
high	O
as	O
433kHz	O
.	O
</s>
<s>
Because	O
long-wave	B-Algorithm
signals	O
can	O
travel	O
very	O
long	O
distances	O
,	O
some	O
radio	O
amateurs	O
and	O
shortwave	O
listeners	O
engage	O
in	O
an	O
activity	O
called	O
DXing	O
.	O
</s>
<s>
Reception	O
of	O
long-wave	B-Algorithm
signals	O
at	O
distances	O
in	O
excess	O
of	O
have	O
been	O
verified	O
.	O
</s>
