<s>
Klein	B-Algorithm
Heidelberg	I-Algorithm
(	O
KH	O
)	O
was	O
a	O
passive	B-Algorithm
radar	I-Algorithm
system	O
deployed	O
by	O
the	O
Germans	O
during	O
World	O
War	O
II	O
.	O
</s>
<s>
In	O
modern	O
terminology	O
,	O
the	O
system	O
was	O
a	O
bistatic	B-Algorithm
radar	I-Algorithm
.	O
</s>
<s>
Because	O
the	O
system	O
sent	O
no	O
signals	O
of	O
its	O
own	O
,	O
the	O
allies	O
were	O
unaware	O
of	O
its	O
presence	O
,	O
and	O
did	O
not	O
learn	O
of	O
the	O
system	O
until	O
well	O
after	O
the	O
D-Day	B-Application
invasion	O
.	O
</s>
<s>
The	O
system	O
is	O
referred	O
to	O
as	O
Klein	B-Algorithm
Heidelberg	I-Algorithm
Parasit	I-Algorithm
(	O
Small	O
Heidelberg	O
Parasite	O
)	O
in	O
some	O
references	O
.	O
</s>
<s>
Beginning	O
in	O
1942	O
,	O
Dr.	O
Wächter	O
of	O
Telefunken	O
,	O
working	O
with	O
radio	O
engineers	O
at	O
the	O
Reichspost	O
,	O
used	O
this	O
information	O
to	O
build	O
a	O
passive	B-Algorithm
radar	I-Algorithm
system	O
using	O
the	O
CH	O
broadcasts	O
and	O
their	O
own	O
receivers	O
.	O
</s>
<s>
Another	O
side-effect	O
of	O
the	O
long	O
wavelength	O
was	O
that	O
the	O
angular	O
resolution	O
was	O
relatively	O
low	O
,	O
and	O
although	O
a	O
lobe	B-Algorithm
switching	I-Algorithm
system	O
was	O
considered	O
,	O
it	O
was	O
apparently	O
never	O
used	O
in	O
service	O
.	O
</s>
<s>
The	O
first	O
operational	O
KH	O
system	O
was	O
built	O
at	O
the	O
Nachtfalter	O
(	O
Moth	O
)	O
jamming	O
station	O
at	O
Mont	O
de	O
Couple	O
between	O
Boulogne	O
and	O
Calais	B-General_Concept
,	O
across	O
the	O
English	O
Channel	O
from	O
Dover	O
,	O
which	O
became	O
operational	O
near	O
the	O
end	O
of	O
1943	O
.	O
</s>
<s>
Today	O
,	O
this	O
is	O
known	O
as	O
the	O
bistatic	B-Algorithm
range	I-Algorithm
.	O
</s>
<s>
Given	O
the	O
lack	O
of	O
lobe	B-Algorithm
switching	I-Algorithm
,	O
the	O
angle	O
accuracy	O
was	O
more	O
on	O
the	O
order	O
of	O
10	O
degrees	O
( +	O
or	O
-5	O
degrees	O
)	O
.	O
</s>
