<s>
HamSphere	B-Protocol
is	O
a	O
subscription-based	O
internet	O
service	O
that	O
simulates	O
amateur	O
radio	O
communication	O
using	O
VoIP	B-Application
connections	O
over	O
the	O
Internet	O
.	O
</s>
<s>
In	O
general	O
,	O
it	O
is	O
similar	O
to	O
other	O
VoIP	B-Application
applications	O
(	O
such	O
as	O
Skype	B-Application
)	O
,	O
but	O
with	O
the	O
unique	O
addition	O
of	O
characteristics	O
such	O
as	O
channel	O
selection	O
by	O
tuning	O
,	O
modulation	O
,	O
noise	O
effects	O
and	O
shortwave	O
propagation	O
simulation	O
.	O
</s>
<s>
The	O
HamSphere	B-Protocol
system	O
relies	O
on	O
different	O
amateur	O
online	O
callbooks	O
for	O
verification	O
before	O
his	O
or	O
her	O
call	O
sign	O
is	O
added	O
to	O
the	O
list	O
of	O
validated	O
users	O
.	O
</s>
<s>
The	O
system	O
may	O
be	O
used	O
without	O
a	O
verified	O
radio	O
amateur	O
license	O
and	O
has	O
a	O
callsign	O
generator	O
providing	O
unique	O
unofficial	O
HamSphere	B-Protocol
callsigns	O
.	O
</s>
<s>
The	O
software	O
is	O
written	O
to	O
run	O
on	O
Microsoft	O
Windows	O
,	O
Apple	O
OS	O
X	O
or	O
Linux	O
using	O
Java	B-Device
.	O
</s>
<s>
Operators	O
using	O
the	O
HamSphere	B-Protocol
software	O
can	O
operate	O
it	O
in	O
two	O
modes	O
:	O
</s>
<s>
This	O
is	O
the	O
unique	O
feature	O
of	O
HamSphere	B-Protocol
allowing	O
the	O
user	O
to	O
maintain	O
connections	O
under	O
natural	O
realistic	O
conditions	O
.	O
</s>
<s>
This	O
mode	O
entails	O
connection	O
to	O
other	O
operators	O
with	O
the	O
reliability	O
of	O
VoIP	B-Application
(	O
noise-free	O
)	O
while	O
maintaining	O
the	O
other	O
typical	O
characteristics	O
of	O
radio	O
communication	O
.	O
</s>
<s>
The	O
HamSphere	B-Protocol
software	O
has	O
two	O
modulation	O
types	O
:	O
</s>
<s>
Single-sideband	B-Device
suppressed-carrier	I-Device
transmission	I-Device
or	O
SSB	O
is	O
the	O
default	O
mode	O
of	O
operation	O
where	O
the	O
operator	O
uses	O
speech	O
audio/phone	O
.	O
</s>
<s>
Signals	O
are	O
received	O
and	O
converted	O
into	O
audible	O
form	O
by	O
using	O
a	O
product	O
detector	O
mixing	O
the	O
local	O
oscillator	O
signal	O
with	O
the	O
received	O
signal	O
,	O
very	O
similar	O
to	O
Software-defined	B-Architecture
radio	I-Architecture
.	O
</s>
<s>
The	O
digital	B-Algorithm
artifact	I-Algorithm
of	O
the	O
decoded	O
audio	O
signal	O
is	O
later	O
filtered	O
with	O
a	O
17-order	O
FIR	O
filter	O
with	O
a	O
bandwidth	O
of	O
2.8kHz	O
.	O
</s>
