Aircraft Radio Corporation SCR-274-N, Operating Instructions Manual, Page: 7 / 32

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Section I
Paragraphs
1-2
AN 08-40SCR274-2
SAFETY NOTICE
This equipment employs high voltages which are dangerous and may be fatal
if contacted by operating personnel. Extreme caution should be exercised when
working with the equipment.
SECTION I
GENERAL DESCRIPTION
I. GENERAL
(See figure 1-1.)
a.
Radio Set SCn.-274-N is a multichannel aircraft
radio receiving and transmitting equipment. The radio
set consists basically of a group of three receivers and
a group of two or four transmitters, each group with
its special rack and mounting. The set can be remotely
or locally controlled.
h.
The frequency ranges of the radio receivers
(fig.
1-2)
of Radio Set SCR-724-N are as follows:
Receiver
Frequency
Radio R�ceiver
BC-453-A
or
BC-453-B ...... 190-550
kilocycles
Radio Receiver
BC-454-A
or
BC-454-B ...... 3.0-6.0
megacycles
Radio Receiver
BC-455-A
or
BC-455-B ...... 6.0-9.1
megacycles
Radio Receiver BC-946-B ................. 0.52-1.5 megacycles
c.
The frequency ranges of the radio transmitters
(fig. 1-3)
of Radio Set SCR-274-N are as follows:
2.
EQUIPMENT SUPPLIED.
The following table lists the equipment supplied:
a.
RECEIVING EQUIPMENT.
(See figures 1-1 to 1-11.)
Transmitter
Frequency
(in megacycles)
Radio Transmitter BC-696-A ......................... 3.0-4.0
Radio Transmitter
BC-457-A ........................ .4.0-5.3
Radio Transmitter
BC-458-A ........................... 5.3-7 .
Radio Transmitter BC-459-A ......................... 7.0-9.1
d.
The receivers receive continuous wave ( cw) , or
amplitude modulated . continuous waves (mcw) , while
the transmitters transmit on tone or voice.
e.
Primary power is obtained from the 24- to 28-volt
d-c supply on the airplane. The current drain is 1.6
amperes per receiver for a normal input of 28 volts.
The current drain in a two-transmitter installation at
28 volts input is 9 amperes at maximum power output
and 2.5 amperes when not transmitting. (The peak
power output of each transmitter under optimum an­
tenna loading conditions exceeds 40 watts on
cw
for
28 volts input.)
(1) FOR THREE-RECEIVER INSTALLATION. The following parts are supplied for this type of installation:
Quantity per Name of Unit Army Type Navy Type Overall Dimensions Weight
Equipment Designation Designation (inches) (pounds)
1 each Radio Receivers BC-453-A
*
427�
x
7%
X
527� 5.7
(BC-453-B)
BC-454-A 42�
x
7%
x
527� 5.7
(BC-454-B)
BC-455-A
427�
x
7%
X
527� 5.7
(BC-455-B)
3 Dynamotor
DM-32-A
3.0
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