2-8
2.5
lnstalling the Transponder
Antennas
DMNI
70-1
orANT
2000
The transponder antenna
is
fitted
to
the underside
of
the
aircraft
fuselage at a horizontal, flat location
in the longitudinal
direction.
This location should
not
be in the , shadow
"of
aircraft structure items. The
highest range
is
achieved when the antenna
is
located at the
low
point
on the aircraft fuselage. The installation
dimensions
of
the
transpe>nder
antennas
DMN
1
70-1
are
shown
in
Fig.
2-6
those
of
the
antenna
AI\IT 2000
in Fig. 2-7.
• Transponder antenna DMNI
70-1
is
provided
with
a cork gasket which must
be
interposed between
the skin
of
the
aircraft
and the antenna.
To
mount
the antenna
use
only
stainless screws in conjunction
with
lock
washers.
e The transponder antenna
ANT
2000
is
provided vvith a silicone rubber gasket which must also
be
interposed between
the
skin
of
the aircraft and the antenna.
• ln aircraft having a wooden or plastic airframe
an
electric
counterweight
plate
or
panel
must
be
located
within
the fuselage at the antenna location
with
minimum
dimension
40
x
40
cm.
2.5.1 Antenna Feeder
Use
type
RG
58 C/U coaxial cable when a length
of
3 m
or
less
is
required.
Use
type
RG
213/U when the
length exceeds 3 m.
Keep
the antenna feeder
as
short
as
possible
so
that
as
little
power
is
dissipated in the cable
as
possible.
2.5.2 DME -Suppression
If
required, connect the suppression
in/out
(Pin 10
of
J 4204)
of
ATC
2000
with
the corresponding pin
of
the DME connector
with
type
RG
178 B/U cable.
2.6 Checking after
Installation
2.6.1 General
After
the installation, check the transponder
to
ensure satisfactory operation
of
the unit. The transmit
frequency
is
to
be
checked and
to
be
adjusted
if
necessary.
2.6.2 Checking
Procedure
Carry
out
post installation check following the description
of
2.2.2
to
2.2.9 utilizing a ramp test set.
2.6.3 Test and adjustment of transmit frequency
Set
code
0000
on
the
tronsponder
ond
mode
A in;:crrogotion
on
the
romp
test
set.
Check
transmit
frequcncy
by
means
of
the ramp test set. Transmit frequency must be 1
090
± 2
MHz.
1 f necessary
use
special wren
ch
(1
/4")
loosen
trimmnut
through the hale in the
top
caver
(see
fig.
2-8) and
ad
just transmit frequency
by
means
of
the tuning screw.
After
adjustment carefully
tighten
the
trimmnut.
09/80
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The document reference is online, please check the correspondence between the online documentation and the printed version.
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