<s>
Fldigi	B-Protocol
(	O
short	O
for	O
Fast	O
light	O
digital	O
)	O
is	O
a	O
free	B-License
and	I-License
open-source	I-License
program	O
which	O
allows	O
an	O
ordinary	O
computer	O
's	O
sound	B-Device
card	I-Device
to	O
be	O
used	O
as	O
a	O
simple	O
two-way	O
data	B-Application
modem	I-Application
.	O
</s>
<s>
The	O
software	O
is	O
mostly	O
used	O
by	O
amateur	O
radio	O
operators	O
who	O
connect	O
the	O
microphone	B-Application
and	O
headphone	B-Device
connections	O
of	O
an	O
amateur	O
radio	O
SSB	B-Device
or	O
FM	B-Application
transceiver	O
to	O
the	O
computer	O
's	O
headphone	B-Device
and	O
microphone	B-Application
connections	O
,	O
respectively	O
.	O
</s>
<s>
This	O
interconnection	O
creates	O
a	O
"	O
sound	B-Device
card	I-Device
defined	O
radio	O
"	O
whose	O
available	O
bandwidth	B-Algorithm
is	O
limited	O
by	O
the	O
sound	B-Device
card	I-Device
's	O
sample	O
rate	O
and	O
the	O
external	O
radio	O
's	O
bandwidth	B-Algorithm
.	O
</s>
<s>
Such	O
communications	O
are	O
normally	O
done	O
on	O
the	O
shortwave	O
amateur	B-Algorithm
radio	I-Algorithm
bands	I-Algorithm
in	O
modes	O
such	O
as	O
PSK31	B-Device
,	O
MFSK	B-Device
,	O
RTTY	O
,	O
Olivia	B-Device
,	O
and	O
CW	O
(	O
Morse	O
code	O
)	O
.	O
</s>
<s>
Increasingly	O
,	O
the	O
software	O
is	O
also	O
being	O
used	O
for	O
data	O
on	O
VHF	B-Algorithm
and	O
UHF	O
frequencies	O
using	O
faster	O
modes	O
such	O
as	O
8-PSK	O
.	O
</s>
<s>
Fldigi	B-Protocol
software	O
is	O
also	O
used	O
for	O
amateur	O
radio	O
emergency	O
communications	O
when	O
other	O
communication	O
systems	O
fail	O
due	O
to	O
natural	O
disaster	O
or	O
power	O
outage	O
.	O
</s>
<s>
Fldigi	B-Protocol
is	O
based	O
on	O
the	O
lightweight	O
portable	B-Architecture
graphics	O
library	O
FLTK	B-Language
and	O
the	O
C/C	O
++	O
language	O
.	O
</s>
<s>
Because	O
of	O
this	O
,	O
the	O
software	O
can	O
run	O
on	O
many	O
different	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
:	O
</s>
<s>
Linux	B-Application
,	O
</s>
<s>
FreeBSD	B-Operating_System
,	O
</s>
<s>
OpenBSD	B-Operating_System
,	O
</s>
<s>
NetBSD	B-Device
,	O
</s>
<s>
Solaris	B-Application
.	O
</s>
<s>
Additionally	O
,	O
Fldigi	B-Protocol
is	O
designed	O
to	O
compile	O
and	O
run	O
on	O
any	O
POSIX	O
compliant	O
operating	B-General_Concept
system	I-General_Concept
that	O
uses	O
an	O
X11	B-Operating_System
compatible	O
window	O
system	O
/	O
graphical	B-Application
user	I-Application
interface	I-Application
.	O
</s>
<s>
The	O
Fldigi	B-Protocol
software	O
is	O
written	O
in	O
highly	O
portable	B-Architecture
C/C	O
++	O
and	O
can	O
be	O
used	O
on	O
many	O
CPU	B-General_Concept
architectures	B-General_Concept
,	O
including	O
:	O
</s>
<s>
Raspberry	B-Operating_System
Pi	I-Operating_System
.	O
</s>
<s>
Multiple	O
sound	O
systems	O
are	O
supported	O
by	O
Fldigi	B-Protocol
,	O
allowing	O
the	O
program	O
to	O
abstract	O
the	O
sound	B-Device
card	I-Device
hardware	O
across	O
differing	O
hardware	O
and	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Control	O
of	O
external	O
transmit	O
/	O
receive	O
radio	O
hardware	O
by	O
using	O
GPIO	B-Architecture
pins	O
.	O
</s>
<s>
The	O
"	O
Fldigi	B-Protocol
Suite	O
"	O
consists	O
of	O
the	O
Fldigi	B-Protocol
modem	B-Application
and	O
all	O
extension	B-Application
programs	O
released	O
by	O
the	O
same	O
development	O
group	O
.	O
</s>
<s>
Most	O
of	O
these	O
extensions	O
add	O
more	O
capabilities	O
to	O
Fldigi	B-Protocol
such	O
as	O
verified	O
file	O
transfer	O
and	O
message	O
passing	O
.	O
</s>
<s>
Interconnection	O
between	O
these	O
programs	O
and	O
the	O
Fldigi	B-Protocol
modem	B-Application
is	O
made	O
over	O
TCP/IP	B-Protocol
port	B-Protocol
7322	O
.	O
</s>
<s>
Some	O
of	O
the	O
Suite	O
are	O
however	O
standalone	O
programs	O
used	O
for	O
utility	O
or	O
testing	O
purposes	O
only	O
,	O
with	O
no	O
connection	O
to	O
the	O
Fldigi	B-Protocol
main	O
modem	B-Application
.	O
</s>
<s>
This	O
program	O
is	O
useful	O
for	O
multicasting	O
files	O
over	O
lossy	O
connections	O
such	O
as	O
those	O
found	O
on	O
High	B-Algorithm
frequency	I-Algorithm
(	O
HF	O
)	O
or	O
during	O
emergency	O
communications	O
.	O
</s>
<s>
Flarq	O
implements	O
the	O
ARQ	B-Error_Name
specification	O
developed	O
by	O
Paul	O
Schmidt	O
,	O
K9PS	O
to	O
transfer	O
emails	O
,	O
text	B-General_Concept
files	I-General_Concept
,	O
images	O
,	O
and	O
binary	O
files	O
over	O
radio	O
.	O
</s>
<s>
This	O
protocol	O
is	O
unicast	B-Protocol
and	O
connection-based	O
.	O
</s>
<s>
The	O
software	O
seamlessly	O
integrates	O
with	O
existing	O
email	O
clients	O
such	O
as	O
Microsoft	B-Application
Outlook	I-Application
,	O
Mozilla	B-Application
Thunderbird	I-Application
,	O
and	O
Sylpheed	B-Language
.	O
</s>
<s>
This	O
is	O
a	O
Morse	O
code	O
keyer	B-Device
which	O
is	O
adjustable	O
via	O
computer	O
commands	O
over	O
USB	B-Protocol
.	O
</s>
<s>
It	O
does	O
not	O
connect	O
to	O
Fldigi	B-Protocol
.	O
</s>
<s>
Flaa	O
is	O
a	O
control	O
program	O
for	O
use	O
with	O
the	O
RigExpert	O
AA-xxxx	O
series	O
of	O
antenna	O
analyzers	O
,	O
and	O
does	O
not	O
connect	O
to	O
Fldigi	B-Protocol
.	O
</s>
<s>
FLRig	O
is	O
a	O
component	O
of	O
the	O
FLDigi	B-Protocol
suite	O
of	O
applications	O
that	O
enables	O
computer	O
aided	O
control	O
of	O
various	O
radios	O
using	O
a	O
serial	O
or	O
USB	B-Protocol
connection	O
.	O
</s>
<s>
Using	O
FLRig	O
in	O
combination	O
with	O
FLDigi	B-Protocol
,	O
events	O
such	O
as	O
frequency	O
,	O
power	O
level	O
,	O
receiver	O
gain	O
and	O
audio	O
gain	O
may	O
be	O
adjusted	O
from	O
the	O
computer	O
automatically	O
or	O
by	O
user	O
intervention	O
.	O
</s>
<s>
The	O
Fldigi	B-Protocol
development	O
group	O
also	O
releases	O
a	O
number	O
of	O
open-source	O
programs	O
which	O
assist	O
in	O
the	O
testing	O
,	O
development	O
,	O
and	O
comparison	O
of	O
different	O
modes	O
within	O
Fldigi	B-Protocol
.	O
</s>
<s>
Currently	O
7	O
sound	O
card-digital-modem	O
programs	O
support	O
this	O
standard	O
:	O
</s>
<s>
This	O
burst	O
consists	O
of	O
a	O
10.766baud	O
16-tone	O
MFSK	B-Device
modulation	O
where	O
15	O
tones/symbols	O
are	O
sent	O
.	O
</s>
<s>
The	O
burst	O
occupies	O
172Hz	O
of	O
bandwidth	B-Algorithm
and	O
lasts	O
for	O
1.4	O
seconds	O
.	O
</s>
<s>
For	O
simple	O
keyboard-to-keyboard	O
communication	O
Fldigi	B-Protocol
can	O
be	O
operated	O
using	O
just	O
the	O
main	O
window	O
.	O
</s>
<s>
For	O
more	O
complex	O
uses	O
or	O
file	O
transfer	O
external	O
programs	O
can	O
be	O
attached	O
to	O
the	O
internal	O
TCP/UDP	O
ports	O
7322	O
(	O
ARQ	B-Error_Name
)	O
,	O
7342	O
(	O
KISS	B-Protocol
)	O
,	O
and	O
7362	O
(	O
XML-RPC	O
)	O
.	O
</s>
<s>
The	O
image	O
below	O
helps	O
to	O
illustrate	O
the	O
interconnections	O
and	O
signal-flow	O
within	O
the	O
Fldigi	B-Protocol
architecture	O
.	O
</s>
<s>
Fldigi	B-Protocol
allows	O
external	O
programs	O
to	O
attach	O
and	O
send	O
/	O
receive	O
data	O
by	O
connecting	O
to	O
port	B-Protocol
7322/ARQ	O
or	O
7342/KISS	O
.	O
</s>
<s>
When	O
used	O
this	O
way	O
,	O
Fldigi	B-Protocol
and	O
the	O
computer	O
's	O
sound	B-Device
card	I-Device
are	O
acting	O
as	O
a	O
"	O
softmodem	B-Device
"	O
allowing	O
text	O
or	O
data	O
sent	O
on	O
one	O
computer	O
to	O
be	O
transferred	O
using	O
the	O
wireless	O
radio	O
link	O
in-between	O
.	O
</s>
<s>
Programs	O
which	O
have	O
a	O
history	O
of	O
use	O
with	O
Fldigi	B-Protocol
as	O
the	O
underlying	O
modem	B-Application
include	O
:	O
</s>
<s>
-	O
attach	O
Fldigi	B-Protocol
as	O
modem	B-Application
for	O
Linux	B-Application
AX.25	B-Protocol
and	O
TCP/IP	B-Protocol
connections	O
.	O
</s>
<s>
Linux	B-Application
-	O
Fldigi	B-Protocol
can	O
be	O
used	O
in	O
Linux	B-Application
as	O
a	O
KISS	B-Protocol
(	O
TNC	O
)	O
modem	B-Application
for	O
AX.25	B-Protocol
and	O
TCP/IP	B-Protocol
connections	O
.	O
</s>
<s>
At	O
the	O
2014	O
Dayton	O
Hamvention	O
the	O
project	O
lead	O
,	O
Dave	O
Freese	O
(	O
W1HKJ	O
)	O
,	O
was	O
recognized	O
with	O
the	O
Technical	O
Excellence	O
Award	O
"	O
for	O
his	O
development	O
and	O
distribution	O
of	O
the	O
Fast	O
Light	O
Digital	O
Modem	B-Application
Application	O
(	O
fldigi	B-Protocol
)	O
family	O
of	O
programs	O
for	O
use	O
in	O
amateur	O
and	O
emergency	O
communications.	O
"	O
</s>
<s>
Following	O
the	O
successful	O
tests	O
by	O
the	O
Voice	O
of	O
America	O
's	O
VOA	O
Radiogram	O
program	O
,	O
international	O
and	O
government	O
shortwave	O
broadcasters	O
began	O
testing	O
and	O
experimenting	O
with	O
digital	O
data	O
over	O
shortwave	O
broadcast	O
channels	O
using	O
the	O
Fldigi	B-Protocol
software	O
.	O
</s>
<s>
In	O
June	O
2017	O
,	O
following	O
the	O
demise	O
of	O
VOA	O
Radiogram	O
,	O
began	O
broadcasting	O
digital	O
data-streams	O
using	O
Fldigi	B-Protocol
via	O
WRMI	O
in	O
Miami	O
and	O
Space	O
Line	O
in	O
Bulgaria	O
.	O
</s>
<s>
The	O
Fldigi	B-Protocol
suite	O
of	O
programs	O
has	O
become	O
popular	O
within	O
the	O
U.S.	O
Army	O
and	O
U.S.	O
Air	O
Force	O
Military	O
Auxiliary	O
Radio	O
System	O
.	O
</s>
<s>
Fldigi	B-Protocol
is	O
used	O
as	O
the	O
underlying	O
modem	B-Application
for	O
the	O
project	O
.	O
</s>
<s>
PSK	B-General_Concept
Mail	O
allows	O
users	O
to	O
retrieve	O
and	O
send	O
normal	O
emails	O
over	O
radio	O
.	O
</s>
<s>
In	O
2014	O
,	O
the	O
group	O
Anonymous	O
released	O
a	O
communications	O
tool	O
named	O
AirChat	O
,	O
which	O
used	O
Fldigi	B-Protocol
as	O
the	O
underlying	O
modem	B-Application
.	O
</s>
<s>
The	O
broadcasts	O
listed	O
below	O
are	O
transmitted	O
on	O
a	O
regular	O
schedule	O
and	O
can	O
be	O
decoded	O
using	O
Fldigi	B-Protocol
.	O
</s>
