<s>
Medium	B-Algorithm
frequency	I-Algorithm
(	O
MF	O
)	O
is	O
the	O
ITU	O
designation	O
for	O
radio	O
frequencies	O
(	O
RF	O
)	O
in	O
the	O
range	O
of	O
300kilohertz	O
(	O
kHz	O
)	O
to	O
3megahertz	O
(	O
MHz	O
)	O
.	O
</s>
<s>
Part	O
of	O
this	O
band	O
is	O
the	O
medium	O
wave(MW )	O
AM	B-Device
broadcast	O
band	O
.	O
</s>
<s>
Frequencies	O
immediately	O
below	O
MF	O
are	O
denoted	O
low	B-Algorithm
frequency	I-Algorithm
(	O
LF	B-Algorithm
)	O
,	O
while	O
the	O
first	O
band	O
of	O
higher	O
frequencies	O
is	O
known	O
as	O
high	B-Algorithm
frequency	I-Algorithm
(	O
HF	B-Algorithm
)	O
.	O
</s>
<s>
MF	O
is	O
mostly	O
used	O
for	O
AM	B-Device
radio	O
broadcasting	O
,	O
navigational	O
radio	O
beacons	O
,	O
maritime	O
ship-to-shore	O
communication	O
,	O
and	O
transoceanic	O
air	B-Application
traffic	I-Application
control	I-Application
.	O
</s>
<s>
Typical	O
MF	B-Algorithm
radio	I-Algorithm
stations	O
can	O
cover	O
a	O
radius	O
of	O
several	O
hundred	O
miles	O
from	O
the	O
transmitter	O
,	O
with	O
longer	O
distances	O
over	O
water	O
and	O
damp	O
earth	O
.	O
</s>
<s>
However	O
,	O
at	O
certain	O
times	O
the	O
D	O
layer	O
(	O
at	O
a	O
lower	O
altitude	O
than	O
the	O
refractive	O
E	O
and	O
F	O
layers	O
)	O
can	O
be	O
electronically	O
noisy	O
and	O
absorb	O
MF	B-Algorithm
radio	I-Algorithm
waves	O
,	O
interfering	O
with	O
skywave	O
propagation	O
.	O
</s>
<s>
When	O
this	O
happens	O
,	O
MF	B-Algorithm
radio	I-Algorithm
waves	O
can	O
easily	O
be	O
received	O
hundreds	O
or	O
even	O
thousands	O
of	O
miles	O
away	O
as	O
the	O
signal	O
will	O
be	O
refracted	O
by	O
the	O
remaining	O
F	O
layer	O
.	O
</s>
<s>
The	O
North	O
American	O
Regional	O
Broadcasting	O
Agreement	O
(	O
NARBA	O
)	O
sets	O
aside	O
certain	O
channels	O
for	O
nighttime	O
use	O
over	O
extended	O
service	O
areas	O
via	O
skywave	O
by	O
a	O
few	O
specially	O
licensed	O
AM	B-Device
broadcasting	O
stations	O
.	O
</s>
<s>
in	O
Europe	O
;	O
in	O
North	O
America	O
this	O
extends	B-Algorithm
from	O
525kHz	O
to	O
1705kHz	O
Some	O
countries	O
also	O
allow	O
broadcasting	O
in	O
the	O
120-meter	B-Algorithm
band	I-Algorithm
from	O
2300	O
to	O
2495kHz	O
;	O
these	O
frequencies	O
are	O
mostly	O
used	O
in	O
tropical	O
areas	O
.	O
</s>
<s>
Although	O
these	O
are	O
medium	B-Algorithm
frequencies	I-Algorithm
,	O
120	O
meters	O
is	O
generally	O
treated	O
as	O
one	O
of	O
the	O
shortwave	B-Algorithm
bands	I-Algorithm
.	O
</s>
<s>
Non-directional	O
navigational	O
radio	O
beacons	O
(	O
NDBs	O
)	O
for	O
maritime	O
and	O
aircraft	O
navigation	O
occupy	O
a	O
band	O
from	O
190	O
to	O
435kHz	O
,	O
which	O
overlaps	O
from	O
the	O
LF	B-Algorithm
into	O
the	O
bottom	O
part	O
of	O
the	O
MF	O
band	O
.	O
</s>
<s>
2182	O
kHz	O
is	O
the	O
international	O
calling	O
and	O
distress	O
frequency	O
for	O
SSB	B-Device
maritime	O
voice	O
communication	O
(	O
radiotelephony	O
)	O
.	O
</s>
<s>
Lastly	O
,	O
there	O
are	O
aeronautical	O
and	O
other	O
mobile	O
SSB	B-Device
bands	O
from	O
2850kHz	O
to	O
3500kHz	O
,	O
crossing	O
the	O
boundary	O
from	O
the	O
MF	O
band	O
into	O
the	O
HF	B-Algorithm
radio	I-Algorithm
band	O
.	O
</s>
<s>
An	O
amateur	O
radio	O
band	O
known	O
as	O
160	B-Algorithm
meters	I-Algorithm
or	O
'	O
top-band	O
'	O
is	O
between	O
1800	O
and	O
2000kHz	O
(	O
allocation	O
depends	O
on	O
country	O
and	O
starts	O
at	O
1810kHz	O
outside	O
the	O
Americas	O
)	O
.	O
</s>
<s>
Amateur	O
operators	O
transmit	O
CW	O
morse	O
code	O
,	O
digital	O
signals	O
and	O
SSB	B-Device
and	O
AM	B-Device
voice	O
signals	O
on	O
this	O
band	O
.	O
</s>
<s>
The	O
most	O
common	O
receiving	O
antenna	O
is	O
the	O
ferrite	O
loopstick	B-Architecture
antenna	O
(	O
also	O
known	O
as	O
a	O
ferrite	O
rod	O
aerial	O
)	O
,	O
made	O
from	O
a	O
ferrite	O
rod	O
with	O
a	O
coil	O
of	O
fine	O
wire	O
wound	O
around	O
it	O
.	O
</s>
<s>
In	O
addition	O
to	O
their	O
use	O
in	O
AM	B-Device
radios	O
,	O
ferrite	O
antennas	O
are	O
also	O
used	O
in	O
portable	O
radio	B-Device
direction	I-Device
finder	I-Device
(	O
RDF	O
)	O
receivers	O
.	O
</s>
<s>
The	O
ferrite	O
rod	O
antenna	O
has	O
a	O
dipole	O
reception	B-Device
pattern	I-Device
with	O
sharp	O
nulls	O
along	O
the	O
axis	O
of	O
the	O
rod	O
,	O
so	O
that	O
reception	O
is	O
at	O
its	O
best	O
when	O
the	O
rod	O
is	O
at	O
right	O
angles	O
to	O
the	O
transmitter	O
,	O
but	O
fades	O
to	O
nothing	O
when	O
the	O
rod	O
points	O
exactly	O
at	O
the	O
transmitter	O
.	O
</s>
<s>
Other	O
types	O
of	O
loop	B-Architecture
antennas	I-Architecture
and	O
random	O
wire	O
antennas	O
are	O
also	O
used	O
.	O
</s>
