Section II
Paragraph
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�N
08-40SCR274-2
SECTION II
INSTALLATION AND ADJUSTMENT
I. INSTALLATION.
a.
PRELIMINARY PROCEDURE.
(1) COMPONENTS.-Check the list of compo
nents supplied.
(2) MECHANICAL INSPECTJON.-Make the
following checks for obvious mechanical faults.
( a)
Check the operation of controls and dials.
(b)
Check the threads of receptacles and plugs.
( c)
Examine the pin plug assemblies of con-
nectors for bent or otherwise unserviceable units.
( d)
See that proper fuses are in the modulator
unit and receiver rack.
( e)
See that all tubes are securely in place in
their proper sockets.
(f)
Test the grid clips for firmness.
(3) BENCH TEST.-Make an electrical "bench
test" of each component before installation in an air
plane to insure normal operation of the equipment after
installation.
(See fig.
5-4.)
(4) PERMANENT BENCH TEST.-When a con
siderable amount of installation work is to be done,
make a permanent bench test installation which con
sists of:
(a)
Test Set RC-54-A, (RC-54-B or RC-54-C),
to test the receiving equipment.
(See fig.
5-1
for infor
mation regarding the use of this test set).
Control Unit
MC-237-A may be used for local tuning of the receiver.
(b)
Test Set RC-55-A (RC-55-B or RC-55-C),
to test the transmitting equipment.
(See fig.
5-2
for in
formation regarding the use of this set).
(
c
)
Other items required are Cords
(see fig.
5-3.),
one storage battery (28-volt), one Headset HS-33 (low
impedence), one Headset Adapter �IC-385- ( ), and one
Microphone T-17 or equal.
h.
INSTALLATION.
(1) ANTENNA.-The exact layout of the antenna
is dictated by the design of the airplane. However, con
sider the following general principals:
( a)
Place the external part of the antenna as
far away from the fuselage as possible.
(b)
Keep the lead-ins inside the fuselage as
short as possible, especially the one to the transmitter.
Use Wire W-I06-A for the internal lead-in. (Insulated
stranded wire may be used for the lead between the
receivers and the antenna relay.)
( c
)
Support the leads on ceramic stand-off insu
lators. When protection against accidental contact with
the aircraft structure is necessary, ceramic beads should
be strung on the wire. The ends of wire must be bent
in close to the metal shells of the bending posts to pre
vent corona and spark breakdown.
(d)
It is recommended that an IRC type, 5 to
25-megohm, 2-watt metalized resistor, or equal be con
nected from antenna to ground at a convenient point
between the antenna binding posts on the receiver and
Antenna Relay Unit BC-442-A or Antenna Unit BC-
442-AM. This will assist in reducing static interferences.
(2) RECEIVERS AND TRANSMITTERS.
( a)
Locate the receivers and transmitters, to
gether with an antenna relay unit, near the antenna
lead-in bushing, in order to keep the interior antenna
lead-in as short as possible. Choose a location that will
permit changing of the receivers and transmitters. The
location for the transmitter must permit a view of the
reflection seen in the mirror on the under side of the
hinged rear cover. Allow enough clearance around the
units
(See figs.
5-5, 5-6,
and
5-7.)
so that under stren
uous vibration they will not strike against anything.
(b)
Mount the receivers and transmitters by
carefully sliding them as far back in their proper rack
compartments as they will go. Slip the locking lugs
over the conical studs and hand screw and safety wire
the knurled nuts which hold the locking lugs in place.
Note
Radio Receiver BC-453-A (or BC-453-B)
should always be placed in the middle section
of Rack FT-220-A. This receiver may be per
manently connected to a separate antenna for
reception of airways radio range signals.
(
c)
Radio Transmitter BC-457-A, BC- 458- A, or
BC-696-A may be installed instead of Radio Transmitter
BC-459-A.
If
the antennas' capacitance is so large that
a transmitter cannot be properly tuned, a 50-micro
microfarad capacitor should be connected in series be
tween posts
"c"
on Antenna Relay Unit BC-442-A.
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