<s>
WSJT-X	B-Protocol
is	O
a	O
computer	O
program	O
used	O
for	O
weak-signal	O
radio	O
communication	O
between	O
amateur	O
radio	O
operators	O
.	O
</s>
<s>
The	O
program	O
was	O
initially	O
written	O
by	O
Joe	O
Taylor	O
,	O
K1JT	O
,	O
but	O
is	O
now	O
open	B-Application
source	I-Application
and	O
is	O
developed	O
by	O
a	O
small	O
team	O
.	O
</s>
<s>
The	O
digital	B-General_Concept
signal	I-General_Concept
processing	I-General_Concept
techniques	O
in	O
WSJT-X	B-Protocol
make	O
it	O
substantially	O
easier	O
for	O
amateur	O
radio	O
operators	O
to	O
employ	O
esoteric	O
propagation	O
modes	O
,	O
such	O
as	O
high-speed	O
meteor	O
scatter	O
and	O
moonbounce	O
.	O
</s>
<s>
Additionally	O
WSJT	B-Protocol
is	O
able	O
to	O
send	O
signal	O
reports	O
to	O
spotting	O
networks	O
such	O
as	O
PSK	O
Reporter	O
.	O
</s>
<s>
WSJT	B-Protocol
,	O
the	O
predecessor	O
to	O
WSJT-X	B-Protocol
,	O
was	O
originally	O
released	O
in	O
2001	O
and	O
has	O
undergone	O
several	O
major	O
revisions	O
.	O
</s>
<s>
Since	O
2005	O
,	O
the	O
software	O
has	O
been	O
released	O
as	O
open	B-Application
source	I-Application
software	I-Application
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
The	O
latest	O
version	O
of	O
WSJT	B-Protocol
(	O
not	O
to	O
be	O
confused	O
with	O
WSJT-X	B-Protocol
)	O
is	O
written	O
in	O
Python	B-Language
and	O
C	B-Language
,	O
with	O
several	O
utilities	O
written	O
in	O
Fortran	B-Application
.	O
</s>
<s>
WSJT	B-Protocol
versions	O
up	O
through	O
7.06	O
r1933	O
(	O
referred	O
to	O
as	O
colloquially	O
as	O
WSJT7	O
)	O
and	O
earlier	O
were	O
aggregations	O
of	O
previous	O
versions	O
,	O
and	O
as	O
such	O
WSJT7	O
contained	O
16	O
different	O
modes	O
(	O
FSK441	B-Protocol
,	O
JT6M	B-Protocol
,	O
JT65	B-Protocol
variants	O
A	O
-	O
C	B-Language
,	O
JT2	O
,	O
JT4	O
variants	O
A	O
-	O
G	O
,	O
WSPR	B-Protocol
,	O
and	O
a	O
preview	O
of	O
JT64A	O
)	O
.	O
</s>
<s>
,	O
the	O
latest	O
WSJT	B-Protocol
version	O
is	O
WSJT10	O
.	O
</s>
<s>
The	O
software	O
carries	O
a	O
general	O
emphasis	O
on	O
weak-signal	O
operation	O
and	O
advanced	O
DSP	B-General_Concept
techniques	O
;	O
however	O
,	O
the	O
communication	O
modes	O
rely	O
upon	O
different	O
ionospheric	O
propagation	O
modes	O
and	O
may	O
be	O
used	O
on	O
many	O
different	O
bands	B-Algorithm
.	O
</s>
<s>
WSJT	B-Protocol
's	O
communication	O
modes	O
can	O
be	O
divided	O
into	O
fast	O
and	O
slow	O
modes	O
.	O
</s>
<s>
As	O
of	O
WSJT10	O
,	O
supported	O
fast	O
modes	O
are	O
JTMS	O
,	O
FSK441	B-Protocol
,	O
ISCAT	O
,	O
and	O
JT6M	B-Protocol
,	O
and	O
the	O
slow	O
modes	O
are	O
JT65	B-Protocol
and	O
JT4	O
.	O
</s>
<s>
WSJT-X	B-Protocol
1.8	O
additionally	O
implements	O
the	O
"	O
slow	O
"	O
JT9	B-Protocol
,	O
FT8	O
,	O
and	O
QRA64	O
.	O
</s>
<s>
Two	O
other	O
modes	O
,	O
WSPR	B-Protocol
and	O
Echo	O
are	O
included	O
for	O
measuring	O
propagation	O
and	O
testing	O
moon	O
bounce	O
echo	O
.	O
</s>
<s>
FSK441	B-Protocol
,	O
introduced	O
in	O
2001	O
as	O
the	O
first	O
communications	O
mode	O
included	O
with	O
WSJT	B-Protocol
,	O
is	O
designed	O
to	O
support	O
communication	O
using	O
streaks	O
of	O
radio-reflecting	O
ions	O
created	O
in	O
the	O
ionosphere	O
by	O
the	O
trails	O
of	O
meteors	O
entering	O
the	O
Earth	O
's	O
atmosphere	O
.	O
</s>
<s>
FSK441	B-Protocol
employs	O
multi-frequency	B-Device
shift	I-Device
keying	I-Device
using	O
four	O
tones	O
,	O
at	O
a	O
data	O
rate	O
of	O
441	O
baud	O
.	O
</s>
<s>
Because	O
of	O
the	O
choice	O
of	O
character	B-General_Concept
codes	I-General_Concept
in	O
the	O
protocol	O
,	O
it	O
is	O
self-synchronizing	O
and	O
does	O
not	O
require	O
an	O
explicit	O
synchronization	O
tone	O
.	O
</s>
<s>
FSK441	B-Protocol
is	O
generally	O
used	O
on	O
the	O
2-meter	B-Algorithm
and	O
70-centimeter	B-Algorithm
amateur	O
bands	B-Algorithm
.	O
</s>
<s>
When	O
transmitted	O
messages	O
include	O
at	O
least	O
one	O
space	O
,	O
the	O
FSK441	B-Protocol
decoding	O
algorithm	O
uses	O
that	O
space	O
character	O
as	O
a	O
syncword	O
for	O
zero-overhead	O
synchronization	O
.	O
</s>
<s>
This	O
mode	O
is	O
no	O
longer	O
included	O
in	O
WSJT-X	B-Protocol
as	O
of	O
version	O
2.1.2	O
.	O
</s>
<s>
JT6M	B-Protocol
,	O
introduced	O
in	O
late	O
2002	O
,	O
is	O
intended	O
for	O
meteor	O
scatter	O
and	O
other	O
ionospheric	O
scattering	O
of	O
signals	O
,	O
and	O
is	O
especially	O
optimized	O
for	O
the	O
6-meter	B-Algorithm
band	I-Algorithm
.	O
</s>
<s>
The	O
mode	O
also	O
employs	O
multiple	B-Device
frequency-shift	I-Device
keying	I-Device
,	O
but	O
at	O
44	O
tones	O
.	O
</s>
<s>
One	O
of	O
the	O
tones	O
is	O
a	O
synchronization	O
tone	O
,	O
leaving	O
43	O
tones	O
to	O
carry	O
data	O
(	O
one	O
tone	O
per	O
character	O
in	O
the	O
character	B-General_Concept
set	I-General_Concept
,	O
which	O
includes	O
alphanumerics	O
and	O
some	O
punctuation	O
)	O
.	O
</s>
<s>
This	O
mode	O
is	O
no	O
longer	O
included	O
in	O
WSJT-X	B-Protocol
as	O
of	O
version	O
2.1.2	O
.	O
</s>
<s>
JT65	B-Protocol
,	O
developed	O
and	O
released	O
in	O
late	O
2003	O
,	O
is	O
intended	O
for	O
extremely	O
weak	O
but	O
slowly	O
varying	O
signals	O
,	O
such	O
as	O
those	O
found	O
on	O
troposcatter	O
or	O
Earth-Moon-Earth	O
(	O
EME	O
,	O
or	O
"	O
moonbounce	O
"	O
)	O
paths	O
.	O
</s>
<s>
It	O
can	O
decode	O
signals	O
many	O
decibels	O
below	O
the	O
noise	O
floor	O
in	O
a	O
2500Hz	O
band	O
(	O
note	O
that	O
SNR	O
in	O
a	O
2500Hz	O
band	O
is	O
approximately	O
28dB	O
lower	O
than	O
SNR	O
in	O
a	O
4Hz	O
band	O
,	O
which	O
is	O
closer	O
to	O
the	O
channel	O
bandwidth	O
of	O
an	O
individual	O
JT65	B-Protocol
tone	O
)	O
,	O
and	O
can	O
often	O
allow	O
amateurs	O
to	O
successfully	O
exchange	O
contact	O
information	O
without	O
signals	O
being	O
audible	O
to	O
the	O
human	O
ear	O
.	O
</s>
<s>
Like	O
the	O
other	O
modes	O
,	O
multiple-frequency	O
shift	O
keying	O
is	O
employed	O
;	O
unlike	O
the	O
other	O
modes	O
,	O
messages	O
are	O
transmitted	O
as	O
atomic	O
units	O
after	O
being	O
compressed	B-General_Concept
and	O
then	O
encoded	O
with	O
a	O
process	O
known	O
as	O
forward	B-Error_Name
error	I-Error_Name
correction	I-Error_Name
(	O
or	O
"	O
FEC	O
"	O
)	O
.	O
</s>
<s>
(	O
The	O
particular	O
code	O
used	O
for	O
JT65	B-Protocol
is	O
Reed-Solomon	B-Error_Name
.	O
)	O
</s>
<s>
After	O
messages	O
are	O
encoded	O
,	O
they	O
are	O
transmitted	O
using	O
MFSK	B-Device
with	O
65	O
tones	O
.	O
</s>
<s>
Operators	O
have	O
also	O
begun	O
using	O
the	O
JT65	B-Protocol
mode	O
for	O
contacts	O
on	O
the	O
HF	B-Algorithm
bands	B-Algorithm
,	O
often	O
using	O
QRP	O
(	O
very	O
low	O
transmit	O
power	O
)	O
;	O
while	O
the	O
mode	O
was	O
not	O
originally	O
intended	O
for	O
such	O
use	O
,	O
its	O
popularity	O
has	O
resulted	O
in	O
several	O
new	O
features	O
being	O
added	O
to	O
WSJT	B-Protocol
in	O
order	O
to	O
facilitate	O
HF	B-Algorithm
operation	O
.	O
</s>
<s>
JT9	B-Protocol
,	O
intended	O
for	O
MF	O
and	O
HF	B-Algorithm
use	O
,	O
was	O
introduced	O
in	O
WSJT-X	B-Protocol
,	O
which	O
was	O
at	O
the	O
time	O
an	O
experimental	O
version	O
of	O
WSJT	B-Protocol
.	O
</s>
<s>
It	O
uses	O
the	O
same	O
logical	O
encoding	O
as	O
JT65	B-Protocol
,	O
but	O
modulates	O
to	O
a	O
9-FSK	O
signal	O
.	O
</s>
<s>
With	O
1-minute	O
transmission	O
intervals	O
,	O
JT9	B-Protocol
occupies	O
less	O
than	O
16Hz	O
bandwidth	O
.	O
</s>
<s>
JT9	B-Protocol
also	O
has	O
versions	O
designed	O
for	O
longer	O
transmission	O
intervals	O
of	O
2	O
minutes	O
,	O
5	O
minutes	O
,	O
10	O
minutes	O
or	O
30	O
minutes	O
.	O
</s>
<s>
Joe	O
Taylor	O
,	O
K1JT	O
,	O
announced	O
on	O
June	O
29	O
,	O
2017	O
,	O
the	O
availability	O
of	O
a	O
new	O
mode	O
in	O
the	O
WSJT-X	B-Protocol
software	O
,	O
FT8	O
.	O
</s>
<s>
Compared	O
to	O
the	O
so-called	O
"	O
slow	O
modes	O
"	O
(	O
JT9	B-Protocol
,	O
JT65	B-Protocol
,	O
QRA64	O
)	O
,	O
FT8	O
is	O
a	O
few	O
decibels	O
less	O
sensitive	O
,	O
but	O
allows	O
completion	O
of	O
QSOs	O
four	O
times	O
faster	O
.	O
</s>
<s>
Bandwidth	O
is	O
greater	O
than	O
JT9	B-Protocol
,	O
but	O
about	O
one-quarter	O
of	O
JT65A	B-Protocol
and	O
less	O
than	O
one-half	O
of	O
QRA64	O
.	O
</s>
<s>
There	O
are	O
alternative	O
software	O
packages	O
available	O
for	O
JT65	B-Protocol
including	O
MultiPSK	O
(	O
a	O
commercial	O
package	O
developed	O
by	O
F6CTE	O
)	O
,	O
and	O
JT65-HF	O
HB9HQX	O
Edition	O
(	O
a	O
free	B-Application
software	I-Application
package	O
forked	O
from	O
the	O
JT65-HF	O
project	O
developed	O
by	O
W6CQZ	O
)	O
.	O
</s>
<s>
The	O
JT65-HF	O
HB9HQX	O
Edition	O
software	O
,	O
along	O
with	O
the	O
source	O
code	O
,	O
may	O
be	O
obtained	O
from	O
SourceForge	O
.	O
</s>
<s>
An	O
article	O
series	O
on	O
using	O
the	O
original	O
JT65-HF	O
software	O
appeared	O
in	O
CQ	O
Amateur	O
Radio	O
's	O
October	O
&	O
November	O
2010	O
issues	O
.	O
</s>
<s>
And	O
MSHV	O
from	O
LZ2HV	O
recompiled	O
from	O
source	O
code	O
of	O
WSJT-X	B-Protocol
with	O
different	O
GUI	O
implementation	O
both	O
for	O
Linux	O
and	O
Windows	O
OS	O
.	O
</s>
