<s>
WSPR	B-Protocol
(	O
pronounced	O
"	O
whisper	O
"	O
)	O
is	O
an	O
acronym	O
for	O
Weak	O
Signal	O
Propagation	O
Reporter	O
.	O
</s>
<s>
The	O
software	O
code	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
program	O
is	O
designed	O
for	O
sending	O
and	O
receiving	O
low-power	O
transmissions	O
to	O
test	O
propagation	O
paths	O
on	O
the	O
MF	B-Algorithm
and	O
HF	B-Algorithm
bands	O
.	O
</s>
<s>
WSPR	B-Protocol
implements	O
a	O
protocol	O
designed	O
for	O
probing	O
potential	O
propagation	O
paths	O
with	O
low-power	O
transmissions	O
.	O
</s>
<s>
Transmissions	O
carry	O
a	O
station	O
's	O
callsign	O
,	O
Maidenhead	O
grid	O
locator	O
,	O
and	O
transmitter	O
power	O
in	O
dBm	B-General_Concept
.	O
</s>
<s>
The	O
type	B-Device
of	I-Device
radio	I-Device
emission	I-Device
is	O
“	O
F1D	O
”	O
,	O
frequency-shift	O
keying	O
.	O
</s>
<s>
A	O
message	O
contains	O
a	O
station	O
's	O
callsign	O
,	O
Maidenhead	O
grid	O
locator	O
,	O
and	O
transmitter	O
power	O
in	O
dBm	B-General_Concept
.	O
</s>
<s>
The	O
WSPR	B-Protocol
protocol	O
compresses	O
the	O
information	O
in	O
the	O
message	O
into	O
50bits	O
(	O
binary	O
digits	O
)	O
.	O
</s>
<s>
These	O
are	O
encoded	O
using	O
a	O
convolutional	B-Error_Name
code	I-Error_Name
with	O
constraint	B-Error_Name
length	I-Error_Name
K	O
=	O
32	O
and	O
a	O
rate	O
of	O
r	O
=	O
.	O
</s>
<s>
The	O
long	O
constraint	B-Error_Name
length	I-Error_Name
makes	O
undetected	O
decoding	O
errors	O
less	O
probable	O
,	O
at	O
the	O
cost	O
that	O
the	O
highly	O
efficient	O
Viterbi	B-Algorithm
algorithm	I-Algorithm
must	O
be	O
replaced	O
by	O
a	O
simple	O
sequential	O
algorithm	O
for	O
the	O
decoding	O
process	O
.	O
</s>
<s>
non-recursive	O
convolutional	O
code	O
with	O
constraint	B-Error_Name
length	I-Error_Name
K	O
=	O
32	O
,	O
rate	O
r	O
=	O
.	O
</s>
<s>
Minimum	O
S/N	O
for	O
reception	O
is	O
around	O
–	O
34dB	O
on	O
the	O
WSJT	B-Protocol
scale	O
(	O
2500Hz	O
reference	O
bandwidth	O
)	O
.	O
</s>
<s>
The	O
protocol	O
was	O
designed	O
to	O
test	O
propagation	O
paths	O
on	O
the	O
LF	B-Algorithm
,	O
MF	B-Algorithm
and	O
HF	B-Algorithm
bands	O
.	O
</s>
<s>
Also	O
used	O
experimentally	O
at	O
VHF	B-Algorithm
and	O
higher	O
frequencies	O
.	O
</s>
<s>
Usually	O
a	O
WSPR	B-Protocol
station	O
contains	O
a	O
computer	O
and	O
a	O
transceiver	O
,	O
but	O
it	O
is	O
also	O
possible	O
to	O
build	O
very	O
simple	O
beacon	O
transmitters	O
with	O
little	O
effort	O
.	O
</s>
<s>
For	O
example	O
a	O
simple	O
WSPR	B-Protocol
beacon	O
can	O
be	O
built	O
using	O
the	O
Si570	O
,	O
or	O
Si5351	O
.	O
</s>
<s>
The	O
Raspberry	O
Pi	O
can	O
also	O
be	O
used	O
as	O
WSPR	B-Protocol
beacon	O
.	O
</s>
<s>
In	O
May	O
2021	O
,	O
aerospace	O
engineer	O
Richard	O
Godfrey	O
suggested	O
an	O
examination	O
of	O
historical	O
WSPR	B-Protocol
data	O
to	O
further	O
define	O
the	O
flight	O
path	O
of	O
Malaysian	O
Airlines	O
flight	O
MH370	O
on	O
8	O
March	O
2014	O
,	O
suggesting	O
that	O
there	O
were	O
"	O
518	O
unique	O
transmission	O
paths	O
that	O
cross	O
the	O
area	O
of	O
interest	O
around	O
Malaysia	O
,	O
the	O
Malacca	O
Strait	O
and	O
the	O
Indian	O
Ocean	O
.	O
</s>
<s>
With	O
the	O
WSPR	B-Protocol
data	O
provided	O
every	O
two	O
minutes	O
and	O
the	O
ability	O
to	O
check	O
against	O
the	O
satellite	O
data	O
every	O
hour	O
it	O
is	O
possible	O
to	O
detect	O
and	O
track	O
MH370	O
from	O
two	O
independent	O
sources.	O
"	O
</s>
<s>
In	O
November	O
2021	O
,	O
Godfrey	O
reported	O
that	O
analysis	O
using	O
WSPR	B-Protocol
technology	O
indicated	O
the	O
aircraft	O
flew	O
in	O
circles	O
for	O
around	O
22	O
minutes	O
in	O
an	O
area	O
150	O
nautical	O
miles	O
from	O
the	O
coast	O
of	O
Sumatra	O
before	O
vanishing	O
.	O
</s>
<s>
This	O
new	O
location	O
was	O
identified	O
through	O
extensive	O
analysis	O
of	O
separate	O
data	O
sets	O
,	O
including	O
Inmarsat	O
satellite	O
data	O
,	O
Boeing	O
performance	O
data	O
,	O
oceanographic	O
floating	O
debris	O
drift	O
data	O
,	O
and	O
WSPR	B-Protocol
net	O
data	O
.	O
</s>
<s>
WSPR	B-Protocol
was	O
originally	O
released	O
in	O
2008	O
.	O
</s>
