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and fasten the antenna lead from the radio transmitter
to this bushing by means of the screw provided.
b. Replace the bushing in cover and place the con-
nector over the top of the fairlead, clamping it into
place by means of the screw in the side of the cover.
c. Wind the desired amount of Wire W-106 or
W-106-A on the spool and feed the free end through
the connector clamp and fairlead until it touches the
ground below the airplane.
d.
Connect the free end of the wire to the cable
loop on the Weight WT-7-A or WT-7-B. Considerable
care should be taken in making the connection
between the antenna wire and the weight cable in
order that the joint will run smoothly through the
connector clamp when the antenna is being let out or
reeled in. The loop formed in the antenna wire should
be as small as practicable and the section where the
antenna wire is twisted back upon itself should be
tapered and made as short as a safe joint will permit.
Wind up the antenna wire in the reel until the
Weight WT-7-A or WT-7-B rests securely in the
fairlead socket. Let out and reel in approximately
ten feet of the antenna several times (have someone
pull lightly on the weight to keep the antenna wire
tight) to insure that the connector clamp is working
properly and that the joint between the antenna
wire and weight cable runs smoothly through, the
clamp.
Fairlead Extension F-9 is used when the standard
Fairlead F-8 is not long enough. It consists of Cou-
pling MC-161 and a 36-inch length of standard
phenolic tubing of the same cross section as the tube
of Fairlead F-8. The extension is installed by slipping
Coupling MC-161 over the top of the fairlead tube so
that it covers approximately 3 inches of the tube
and then securing it in place by means of one of the
clamps provided. The tubing may then be clamped
into the coupling by means of the remaining clamp.
This tubing may be cut to fit a particular installation
or more than one extension may be used if required.
9. INTERCONNECTION WITH THE RADIO RE-
CEIVER IN AIRCRAFT
It is necessary, in order to minimize receiver noise,
that the cord shields be well grounded and so sup-
ported that they cannot rub on other cords or metal
surfaces. In order that the radio receiver used be co-
ordinated with the radio transmitter, the receiver
control wires should be connected to terminals 21
and 22 of Plug PL-64. These points are normally
closed but are opened when the key is closed and the
radio transmitter starts functioning.
SECTION III
PREPARATION FOR USE
10.
GENERAL
After installation and before the equipment is put
into operation, the circuits of all cords and ex t erna
wiring should be checked to insure compliance with
the circuit diagram and the applicable intercon-
nection diagram. This circuit check should be made
with all plugs removed from the sockets in the radio
transmitter and power unit to determine that all cord
and junction box connections are made as indicated
on the diagrams. A voltmeter and battery may be
used for this purpose. The plugs should be replaced
in their respective sockets after this check.
11.
RADIO TRANSMITTER BC-375-E
The following procedure is recommended for pre-
paring the radio transmitter for use after installation.
a.
Remove Plug PL-59 from the power unit or
dynamotor unit and cover its socket with a Socket
Cap M-164-A.
b. Remove the tube compartment shielding cover
and insert the tubes. From the front of the radio
transmitter, progressing from left to right, the tubes
are as follows:
Tube VT-25—Speech Amplifier
Tube VT-4-C—Master Oscillator
Tube VT-4-C—Power Amplifier
Tube VT-4-C—Modulator
Tube VT-4-C—Modulator
c. D-c Filament Supply: (Note: This equipment
is not designed for alternating-current operation.)
(1).
Remove all links from the filament resistor
connection board.
(2).
Assuming that the primary source voltage
is 28 V (the terminal voltage of a 24-volt storage
battery under charge), place the 24 V/28 V switch
in the tube compartment in the 28-volt position.
(3).
Set the transmitter signal switch on CW
and the filament voltmeter switch on CW FIL.
(4).
Place the OFF-ON switch in the ON
position. This should start the dynamotor unit and
apply filament supply potential to the radio trans-
mitter, but not to the tubes. Connect link between
adjacent studs on the 28 V and CW FILAMENT
rows. The CW filaments will light and the fila-
ment voltmeter read. Repeat this until the two
studs are found that when connected will cause
3
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