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1.2 The
into
(a)
(h)
(c)
(d)
(e)
(f)
GENERAL PURPOSE COMMUNICATIONS RECEIVER
INSTRUCTIONS
1. GENERAL
1.1 This receiver has been designed for general pur-
pose communication. It is designed to withstand
severe climatic and line voltage variations
without appreciable impairment in performance.
following features have been incorporated
the design of this unit.
Mechanical Band Spread, with Single Con-
trol for ease of tuning a previously logged
station.
Automatic Noise Limiter which automa-
tically limits interference to a percentage of
modulation.
Noise Limiter Switch for switching Noise
Limiter on or off.
Continuously variable High Frequency
Tone Control.
Panel Antenna Trimmer for circuit align-
ment.
Variable selectivity, with expansion of the
normal selectivity characteristic for stand-
by, and a crystal filter for ultra sharp selec-
tivity when required. The crystal filter circuit
is adjusted at the factory to give selectivity
characteristics as shown in Figure 12.
Temperature compensated oscillator circuits
on all bands.
Regulation of the anode voltage of the
oscillator, giving good oscillator stability
through normal' variations in line voltage.
Four-ganged Condenser giving high image
ratio, and very low oscillator radiation on
all bands.
Special screening devices have been built
around the gang condenser, the master oscil-
2. TECHNICAL
lator section, and the r.f. amplifier section in
order to minimize oscillator radiation on all
bands.
(k) Tuning lock for service under extreme con-
ditions of vibration.
Frequency Range:—
Band 1
73 to 205 KC
Band 2
195 to 550 KC
Band 3
1480 to 4400 KC
Band 4
4250 to 12150 KC
Band 5
11900 to 19500 KC
Band 6
19000 to 30500 KC
Sensitivity: Better than 15 microvolts for 20 db
signal to noise ratio, for MCW (A•2)
reception and better than 5 microvolts for
CW (A-1) reception (see table No. 1).
Radiation:—Less than 40 micro-microwatts of
power radiated, as dissipated in resistance con•
nected from Antenna input terminal to ground.
Value of resistance is such as to cause maximum
power to be radiated (see Section 3 below).
Output Power:—(Maximum undistorted)
2.5
Watts when loudspeaker used. When low im-
pedance headphones are used, maximum output
fed to the phones is 100 milliwatts approximate-
ly.
Power Supply Requirements:
115 or 230
volts, 2 5 / 60 cycle, 100 Watts or 6 volts D.C.,
12 amps when external power supply MI.22215
is used. (Note—external power supply MI.22215
is only supplied when specially ordered.)
Output Load:— This receiver has provision in
the output circuit to take loads of 2.5 ohms, 20
ohms, and also low impedance headphones.
Mechanical Specifications:—Overall Dimensions
—191 inches wide x 11 inches high x 194 inches
deep. Weight -- 100 Pounds (unpacked).
DETAILS
(see Section 4.4) with a conventional lead-in
wire. The first tuned circuit is provided with a
trimmer condenser adjustable from the front
panel. This insures the proper tuning of this
circuit with any antenna system.
For all bands, conventional antenna and ground
connections may also be used.
The antenna terminal board is provided with
three terminals (see Figures 3 and 7), two of
which may be joined together with a link. When
a single wire antenna is used, the link should he
closed and the antenna connected to "A". If a
ground is used, it should be connected to "G".
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.1 Circuit Details and Features:—The schematic
diagram of this receiver is shown in Figure 11.
It consists of two stages of R.F. amplification,
first detector, first heterodyne oscillator; three
of I.F. amplification, second detector and
A.V.C., noise limiter, second heterodyne oscil-
lator; A.F. amplifier stage, output power stage,
and power supply system.
2.2 Input Coupling:—The antenna coupling system
is designed to provide optimum coupling from
a 200 ohm transmission line, but equivalent per-
formance is realized with a straight line antenna
[41
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