<s>
An	O
ionosonde	B-Algorithm
,	O
or	O
chirpsounder	O
,	O
is	O
a	O
special	O
radar	B-Application
for	O
the	O
examination	O
of	O
the	O
ionosphere	O
.	O
</s>
<s>
The	O
basic	O
ionosonde	B-Algorithm
technology	O
was	O
invented	O
in	O
1925	O
by	O
Gregory	O
Breit	O
and	O
Merle	O
A	O
.	O
Tuve	O
and	O
further	O
developed	O
in	O
the	O
late	O
1920s	O
by	O
a	O
number	O
of	O
prominent	O
physicists	O
,	O
including	O
Edward	O
Victor	O
Appleton	O
.	O
</s>
<s>
An	O
ionosonde	B-Algorithm
consists	O
of	O
:	O
</s>
<s>
A	O
high	B-Algorithm
frequency	I-Algorithm
(	O
HF	B-Algorithm
)	O
radio	O
transmitter	O
,	O
automatically	O
tunable	O
over	O
a	O
wide	O
range	O
.	O
</s>
<s>
A	O
tracking	O
HF	B-Algorithm
receiver	O
which	O
can	O
automatically	O
track	O
the	O
frequency	O
of	O
the	O
transmitter	O
.	O
</s>
<s>
The	O
transmitter	O
sweeps	O
all	O
or	O
part	O
of	O
the	O
HF	B-Algorithm
frequency	O
range	O
,	O
transmitting	O
short	O
pulses	O
.	O
</s>
<s>
An	O
ionosonde	B-Algorithm
is	O
used	O
for	O
finding	O
the	O
optimum	O
operation	O
frequencies	O
for	O
broadcasts	O
or	O
two-way	O
communications	O
in	O
the	O
high	B-Algorithm
frequency	I-Algorithm
range	O
.	O
</s>
<s>
An	O
ionogram	O
is	O
a	O
display	O
of	O
the	O
data	O
produced	O
by	O
an	O
ionosonde	B-Algorithm
;	O
technically	O
speaking	O
one	O
may	O
call	O
the	O
data	O
used	O
to	O
make	O
the	O
display	O
as	O
the	O
ionogram	O
but	O
often	O
this	O
is	O
simply	O
implied	O
.	O
</s>
<s>
A	O
chirp	B-Application
transmitter	O
is	O
a	O
shortwave	O
radio	O
transmitter	O
that	O
sweeps	O
the	O
HF	B-Algorithm
radio	I-Algorithm
spectrum	O
on	O
a	O
regular	O
schedule	O
.	O
</s>
<s>
If	O
one	O
is	O
monitoring	O
a	O
specific	O
frequency	O
,	O
then	O
a	O
chirp	B-Application
is	O
heard	O
(	O
in	O
CW	O
or	O
SSB	B-Device
mode	O
)	O
when	O
the	O
signal	O
passes	O
through	O
.	O
</s>
<s>
In	O
addition	O
to	O
their	O
use	O
in	O
probing	O
ionospheric	O
properties	O
,	O
these	O
transmitters	O
are	O
also	O
used	O
for	O
over-the-horizon	B-Architecture
radar	I-Architecture
systems	O
.	O
</s>
<s>
An	O
analysis	O
of	O
existing	O
transmitters	O
has	O
been	O
done	O
using	O
SDR	B-Architecture
technology	O
.	O
</s>
<s>
For	O
better	O
identification	O
of	O
chirp	B-Application
transmitters	O
the	O
following	O
notation	O
is	O
used	O
:	O
<repetition rate (s ) >:<chirp offset (s ) >	O
,	O
where	O
the	O
repetition	O
rate	O
is	O
the	O
time	O
between	O
two	O
sweeps	O
in	O
seconds	O
and	O
the	O
chirp	B-Application
offset	O
is	O
the	O
time	O
of	O
the	O
first	O
sweep	O
from	O
0MHz	O
after	O
a	O
full	O
hour	O
in	O
seconds	O
.	O
</s>
