Page
4
ANTENNA
The
BOOMERANG™
antenna
assembly
consists
of
a
rectangular
housing
that
contains
the
actual
antennas.
The
design
and
size
of
the
antenna
is
to
eliminate
any
reflections
coming
from
the
side
or
rear.
The
antenna
housing
also
contains
band
pass
filters
for
the
2
nd
and
3
rd
harmonic
frequencies
to
prevent
any
unwanted
signals
from
reaching
the
receivers.
The
antenna
may
be
mounted
on
the
collapsible
handle
or
used
as
a
hand
‐
held
unit.
Two
LED
barograph
meters
are
mounted
on
the
antenna
in
a
meter
box.
The
meters
give
an
indication
of
the
strength
of
the
received
signals.
The
red
LED
indicator
is
for
the
2
nd
harmonic
and
the
green
LED
is
for
the
3
rd
harmonic.
Visual
comparison
of
the
strengths
of
the
2
nd
and
3
rd
harmonics
will
indicate
whether
the
NJD
has
detected
a
semiconductor
(very
high
2
nd
harmonic,
low
3
rd
)
or
a
corroded
metallic
oxide
(3
rd
harmonic
is
equal
to
or
greater
than
2
nd
).
The
NJD
‐
5
antenna
is
connected
to
the
handle
by
means
of
an
adjustable
swivel.
The
swivel
is
screwed
onto
the
threads
of
the
mounting
bracket
on
the
antenna.
the
swivel
can
be
used
as
a
hand
grip
when
using
the
NJD
in
a
hand
held
mode.
The
male
thread
of
the
bracket
on
the
antenna
has
two
slots
machined
into
it
to
be
used
to
lock
the
antenna
in
certain
orientations.
CABLES
The
NJD
‐
5
electronics
package
contains
a
transmitter
and
receiver.
These
are
connected
to
the
antenna
by
means
of
coaxial
cables.
The
cables
are
8
feet
in
length.
Connectors
for
the
various
elements
are
configured
in
such
a
way
that
it
is
not
possible
to
connect
the
cables
incorrectly.
The
transmitter
cannot
be
connected
to
the
receiver's
antenna
and
vice
versa.
Coaxial
cables
used
at
BOOMERANG™
operating
frequencies
are
very
critical.
Care
should
be
taken
that
the
cables
are
not
overly
strained
by
bending
at
the
connectors,
being
stepped
on,
etc.
If
a
cable
‐
connector
junction
becomes
frayed
or
if
a
degradation
of
performance
occurs,
switch
to
the
other
set
of
cables
supplied
with
the
NJD
‐
5
until
the
connector
can
be
repaired.
The
NJD
is
supplied
with
two
sets
of
coaxial
cables.
The
NJD
‐
5
antenna
mounted
display
is
driven
from
the
electronics
package
via
the
meter
cable.
The
NJD
‐
5
is
supplied
with
an
8
foot
long
meter
cable.
This
cable
also
serves
a
battery
save
purpose.
Power
to
operate
the
NJD
‐
5
is
routed
through
the
meter
cable.
When
the
cable
is
removed
from
its
jack
on
the
NJD
electronics
package,
the
battery
is
disconnected,
making
it
impossible
for
the
NJD
‐
5
to
consume
battery
power
while
in
the
storage
case.
