Page
12
SECTION
5
OPERATIONAL
NOTES
AND
HINTS
"Phantom"
Returns
and
Interfering
Signals
Reflected
Signals
Radio
waves
bounce
or
reflect
off
of
metal
objects.
This
is
true
for
the
signal
transmitted
by
the
NJD
‐
5
and
for
signals
radiated
by
nonlinear
junctions.
Occasionally,
there
will
be
a
metal
surface
on
the
opposite
side
of
a
wall,
for
example,
or
perhaps
in
the
field
of
view
of
the
NJD
‐
5.
This
object,
which
could
be
a
mirror
or
a
metal
cabinet,
will
reflect
the
NJD
‐
5's
signal.
It
is
possible
that
the
signal
could
illuminate
a
nonlinear
junction
that
is
actually
in
back
and
off
to
one
side
of
the
antenna
and
the
radiated
harmonic
might
be
strong
enough
to
reflect
off
the
metal
surface
and
be
detected.
If
one
of
these
"phantom
signals"
is
detected,
changing
the
angle
of
the
antenna
should
eliminate
it.
Visually
inspect
the
other
side
of
the
wall
if
there
is
a
metallic
surface
that
you
can
not
see
from
the
area
being
swept.
Interfering
Signals
In
rare
circumstances,
there
may
be
a
signal
being
detected
by
the
NJD
‐
5
which
appears
to
come
from
all
directions
and
changing
the
direction
the
antenna
is
pointing
in
does
not
eliminate
the
signal.
This
is
caused
by
a
signal
from
another
transmitter
operating
at
exactly
1830
or
2745
MHz.
To
determine
if
this
is
the
case,
place
the
NORMAL/RECEIVE
ONLY
switch
on
the
panel
of
the
electronics
package
in
the
RECEIVE
ONLY
position.
This
turns
off
the
NJD
‐
5's
transmitter.
If
the
interfering
signal
is
caused
by
a
target
creating
a
strong
2
nd
or
3
rd
harmonic
of
the
NJD
‐
5's
transmitted
signal,
turning
off
the
transmitter
will
eliminate
it
and
the
NJD
‐
5’s
LED
meters
will
drop
to
a
low
position.
If
the
interfering
signal
is
being
radiated
by
another
transmitter,
the
meters
will
not
drop
when
the
transmitter
is
turned
off.
The
operator
must
then
locate
the
source
of
the
interfering
signal
by
using
RF
detection
equipment.
The
operator
must
determine
whether
the
signal
is
emanating
from
the
area
being
investigated
or
whether
it
is
emanating
from
outside
of
the
area.
If
the
interfering
signal
can
not
be
turned
off,
the
effectiveness
of
the
NJD
‐
5
will
be
greatly
reduced.
Return
the
switch
to
the
NORMAL
position
after
completing
this
evaluation.
