Hammarlund SP-600-JX-21 Operating instructions

~-------------*--------------;;;
T.O. 31R2-4-10l-2
HANDBOOK
SERVICE INSTRUCTIONS
RADIO RECEIVER
MODEL SP-600-JX-21
(HAMMARLUND)
PUBLISHED UNDER AUTHORITY OF THE SECRETARY OF THE AIR FORCE
:...-_-----------...,...*-------------~
AF, Nunn. & Rimmler, Inc., Cincinnati, Ohio,30C, 8-6S--JlEPRINT
15 JANUARY 1956

T.O. 31R2-4-101-2
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USAF

Section
T.O. 31R2-4-101-2
TABLE OF CONTENTS
Table of Contents
Page
INTRODUCTION 1
I
DESCRIPTION AND LEADING PARTICULARS 1
1-1.
1-4.
1-10.
1-20.
1-33.
General. . .
Purpose and Limitations
Leading Particulars .
Condensed Factual
Data .
Operating and Adjustment Controls
1
1
2
4
7
II TEST EQUIPMENT AND SPECIAL TOOLS .
2-1. Test Equipment. . .
2-3. Special Tools.... ..
2-5. Cable Fabrication .
9
9
9
9
III PREPARATION FOR USE AND RESHIPMENT............... 11
3-1. Preparation for Use ."."'. . 11
3-7. Preparation for Reshipment or Storage .. 11
IV THEORY OF OPERATION 13
4-1. General System Operation 13
4-4. Receiving System Block Diagram 13
4-8. Receiver Functional Operation 13
4-22. Simplified Circuit Theory....... 18
V ORGANIZATIONAL MAINTENANCE 33
5-1. General 33
5-3. Receiver Performance Tests 33
5-6. Trouble Analysis. 33
5-11. Minor Repair and Replacement 39
5-16. Removal and Replacement of Subassemblies 39
5-19. Alignment and Adjustment .. 42
5-23. Preventive Maintenance 43
VI FIELD MAINTENANCE 45
6-1. Trottble Analysis .. 45
6-7. Removal and Replacement 52
6-14. Receiver Alignment and Adjustment 54
6-17. Receiver Performance Tests .. 54
6-19. Preventive Maintenance 54
6-22. Overhaul Schedule 60
VII
DIAGRAMS 61
7-1. General . 61
7-3. Index of Diagrams 61
7-5. Tube-socket Terminal Voltage Diagram.................................. 61
7-7. Tube-so<;ket Terminal Resistance Diagram 61
VIII DIFFERENCE DATA SHEETS ..................................... 65

List of Illustrations
Figure
T.O. 31 R2-4-101-2
LIST OF ILLUSTRATIONS
Page
iv
ii
1-1 Radio Receiver, Model SP-600-JX-21
1-2 Radio Receiver, Front Panel View. 2
1-3 Radio Receiver, Rear View. 3
1-4 Overall Selectivity Curves at Two Megacycles . . 6
1-5 Audio and Overall Fidelity Curves 7
2-1 Special Pliers 9
2-2 Antenna Cable.................... 10
2-3 Cathode-follower Cable . . 10
4-1 Space-diversity Reception of Frequency-shift Signals, System Block Diagram 14
4-2 Radio Receiver, Block Diagram .15
4-3 Radio-frequency Amplifiers, Schematic Diagram ... 17
4-4 Single- and Double-conversion Circuits, Schematic Diagram .19
4-5 Fixed-frequency and Variable-frequency Oscillators, Schematic Diagram ." 20
4-6 455-kc Crystal Filter, Simplified Schematic Diagram 22
4-7 445-kc Intermediate-frequency Amplifier Circuits, Schematic Diagram. 24
4-8 Beat-frequency Oscillator and Buffer Circuits, Schematic Diagram .26
4-9 Detector, Noise-limiter and A-V-C Circuits, Schematic Diagram 27
4-10 Audio Circuits, Schematic Diagram .29
4-11 Power Supply, Schematic Diagram 30
5-1 Receiver Sensitivity Test Setup. 33
5-2 Receiver Cathode-follower Test Setup 37
5-3 Radio Receiver Test-point Location . .. 38
5-4 Radio Receiver, Top View of Chassis 41
5-5 Radio Receiver Alignment Adjustments........ 42
6-1 Receiver Audio Response Test Setup. .... 49
6-2 Receiver Overall Response Test Setup. 53
6-3 Test Setup for Alignment of Receiver I-F Stages. 54
6-4 Alternate Test Setup for Alignment of Receiver I-F Stages. 59
7-1 Radio Receiver, Schematic Diagram 62
7-2 Tube-socket Terminal Voltage Diagram 63
7-3 Tube-socket Terminal Resistance Diagram............................................... 64

T.O. 31R2-4-101-2
LIST OF TABLES
List of Tables
Table Page
I Tube Complement 4
II Fuse Complement . . .... 5
III Tuning Band Ranges........................... 5
IV Image Rejection Ratios 5
V
Test Equipment Required for Maintenance............ 9
VI Special Tools Required for Maintenance 9
VII Power Transformer Tap Voltage Ratings 11
VIII Plug Connector Assemblies Removed from Receiver for Shipment. 11
IX Receiver Performance Tests. 34
X
Power Supply Test-point Data. 37
XI Receiver Sections Test-point Data 40
XII Alignment Frequency and Adjustment Designations .43
XIII Inspection Schedule 43
XIV Troubleshooting..................................... 45
XV Tube-socket Terminal Voltages 49
XVI Tube-socket Terminal Resistances 51
XVII D-C Resistance of Coils and Windings...... 52
XVIII Receiver Alignment and Adjustment Procedures 55
XIX Receiver Performance Tests 58
XX Receiver Overhaul Schedule 60
iii

iv
T.O. 31R2-4-101-2
~"'(;).":': ~ A
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, ,
figure 1-1. Radio Receiver, Model SP-600-JX-21

T.O. 31R2-4-101-2
INTRODUCTION
This handbook has been published to furnish maintenance personnel with.
descriptive information and maintenance instructions for Radio Receiver, Model
SP-600-JX-21, manufactured by the Hammarlund Manufacturing Co., Inc., New
York I,N. Y.
The handbook has been prepared in accordance with Specification MIL-H-
6757 A(ASG). Abbreviations used are in accordance with Air Force-Navy Aeronau-
tical Bulletin No. 261. Electrical and electronic symbols used in the schematic
diagrams conform to Standard JAN-STD-15.
For additional information on the radio receiver, the following publications
should be consulted:
Introduction
Section I
Title
Handbook Operation Instructions
Radio Receiver, Model SP-600-JX-21
Handbook Overhaul Instructions,
Radio Receiver, Model SP-600-JX-21
Illustrated Parts Breakdown,
Radio Receiver, Model SP-600-JX-21
Publication No.
T.O. 31R2-4-101-1
T.O. 31R2-4-101-3
T.O. 31R2-4-101-4
SECTION I
DESCRIPTION
AND LEADING PARTICULARS
1-1. GENERAL.
1-2. This publication comprises service instructions for
Radio Receiver, Model SP-600-JX-21 (figure 1-1),
which is manufactured by the Hammarlund Manufactur-
ing Company, Inc., New York 1, N. Y.
1-3. Sections I through VII of this handbook apply to
the rack mounted version of Radio Receiver, Model
SP-600-JX-21. If additional models become effective, they
will be covered
in Section VIII by the use of Difference
Data Sheets.
1-4. PURPOSE AND LIMITATIONS.
1-5. Radio Receiver, Model SP-600-JX-21, is amulti-
band communications receiver designed for the reception
of A-M radio telephone, cow telegraph, and A-M m-c-w
telegraph signals in the frequency range of 0.54 mc to
54.0 mc.
1-6. The receiver, designed for rtlOunting in astand-
ard 19-inch relay rack, consists of achassis and light
grey front panel assembly to which are mounted a top
cover and a bottom plate. It is intended for use in fixed
and/or mobile operations such as those at enclosed base
stations,
aboard ship, or aboard aircraft, even when such
activities are subjected
to wide ranges in temperature
and humidity. The receiver is treated with fungicidal
varnish
to condition it for tropical use. Its design and
shielding reduce its radiation characteristics to amini-
mum, thereby complying with shipboard regulations and
enabling the receiver to be operated in close proximity
to other station equipment in multi-receiver installations.
It is suited to two-way operational activities and may be
disabled in the presence of a strong local carrier, by
means
of the "SEND/REC" switch (21, figure 1-2).
1-7. The receiver is of the superheterodyne type. It
utilizes six frequency bands for the continuously vari-
able, selective reception
of any signal within the fre-
quency
range of 0.54 to 54.0 me. It has provisions for
fixed-channel crystal-controlled operation on any of six
frequencies
within the range of 0.75 mc to 54.0 mc. In-
coming signals are converted by the heterodyne process
into an intermediate frequency of 455 kc. Single con-
version is used
for signal frequencies up to 7.4 mc, and
double conversion is used for signal frequencies above
7.4 me.
1-8. Various connectors are provided on the front and
rear panels to facilitate use with avariety of signals,
such as
amplitude-modulated, suppressed carrier, keyed
carrier,
and frequency-shift types. For the reception of
radio telephone or low-speed (manual, telegraph sig-
nals, a
headset is plugged in the "PHONES" jack (20,
figure
1-2) located on the front panel, or a loud
speaker is connected to the "AUDIO OUTPUT" ter-
minals (8, figure
1-3) on the rear apron. For high-
speed (automatic) telegraph operation, the receiver doc
output developed between the jumpered "DIODE OUT-
PUT" terminals (2, figure 1-3) and chassis ground,
may be used to operate a tape ink recorder, or the re-
ceiver a-c
output developed at the "AUDIO OUTPUT"
terminals may be used to operate a recorder driving unit
associated with the tape ink recorder. For the reception
of frequency-shift teletype signals, the i-f output de-
veloped at the "IF OUTPUT" connector (6, figure 1-3)
or the a-f output developed at the "AUDIO OUTPUT"
terminals may be used to operate suitable frequency-
shift converter equipment. For the reception of keyed-
carrier, single
or two-tone carrier teletype, the a-f output
1

Section I
Paragraphs 1-9 to 1-11
T.O. 31R2-4-101-2
21
20
7 8
--9
---10
II
18
1. "XT AL PHASING" control
.2. Tuning meter
3. "METER" switch
4.
Main tuning dial
5. "MEGACYCLES" window
6. Vernier dial
7. "6 FREQ" control
8. "FREQ CONTROL" selector switch
9. Plastic
chart
10. "BEAT OSc." control
11. "AVC/MAN" switch
12.
"RF GAIN" control
13. "MOD/CW" switch
14.
"TUNING LOCK"
Figure J-2. Radio Receiver, Front ,Panel View
15. "TUNING" control
16: "AUDIO GAIN" control
17. "BAND CHANGE" control
18. "SELECTIVITY" switch
19.
"LIMITER/OFF" switch
20.
"PHONES" jack
21.
"SEND/REC" switch
developed at the "AUDIO OUTPUT" terminals may be
used to operate suitable demodulator equipment associ-
ated with ateletype-writer.
1-9. The receiver self-contained stabilized power sup-
ply is designed to operate from asingle phase 50- to
60-cyde, a-c source. The power transformer primary is
provided with taps covering aline voltage range from
90 to 270 volts. The receiver is protected against over-
load by fusing the power transformer primary and sec-
ondary plate windings. The primary and secondary fuses
used
are contained respectively in the "LINE" and "-B"
fuse holders (11 and 1, figure 1-3) on the rear apron
of the receiver. Aduplicate of each of these fuses, com-
prising the receiver spare fuse complement, is located
under the polystyrene "SPARK FUSES" cover (10). The
receiver ac power cord (9) can be connected directly to
an a-c power source.
1-10. LEADING PARTICULARS.
1-11. The receiver antenna system used is connected to
the "ANT" input connector (Jl, figure 5-4). The re-
ceiver
input impedance is designed to match a 95-ohm
2
transmission line. A straight wire or balanced doublet
antenna system is used with the receiver. The receiver
rotary turret houses the frequency determining r-f tuner
subassemblies that are used for the six frequency bands
of the receiver. Each frequency band has an antenna,
two identical interstage r-f tuner subassemblles and an
oscillator r-f tuner subassembly. The "BAND CHANGE"
control (17, figure 1-2) is geared to the rotary turret
and is used to select the frequency band desired. It may
be turned in either direction and requires a rotation of
360 degrees to position the rotary turret to adifferent
band.
An indenting mechanism locKs the tuner into
position on each band. The band indicator dial visible
through the "MEGACYCLES" window (5) indicates the
frequency band selected. The "BAND CHANGE" con-
trol (17) positions the movable pointer of the main tun-
ing dial (4) to the proper frequency scale on the dial.
The main dial outer scale is arbitrarily calibrated, and
in conjunction with the vernier dial (6) scale, provides a
continuous vernier scale which facilitates extremely accu-
rate station logging and receiver resettability.

II
10
T.O. 31R2-4-101-2 Section I
Paragraphs 1-12 to 1-14
3'
4
_~--5
1. "-B" fuse
2. "DIODE OUTPUT" terminals
3. "A VC" terminals
4. "BFO IN]" control
5. "METER AD] RF" control
6. "IF OUTPUT" connector
7. "METER AD] AF" control
8. "AUDIO OUTPUT" terminals
9. Power cord
10. "SPARE FUSES" cover
11. "LINE" fuse
12. "AC" power outlet
Figure J-3. Radio Receiver, Rear View
1-12. The "TUNING" control (15, figure 1-2) is fly-
wheel balanced
to provide operating ease. at high trav-
erse speeds.
It controls both the main and vernier dials.
An antibacklash gear train maintains the extremely close
calibration accuracy
and provides for the accurate re-
settability
of the receiver. The "TUNING LOCK" (14)
provides locking action without affecting the frequency
setting.
The tuning ratio from the tuning control to the
main dial is 50 to one and the ratio from the vernier
dial to the main dial is six to one.
1-13. The receiver circuitry available for single con-
version includes
two stages of r-f amplification, amixer,
a
heterodyne oscillator, four stages of i-f amplification,
a
detector and an a-v-c rectifier, anoise limiter and a
meter rectifier, abeat-frequency oscillator, abeat-
frequency buffer amplifier, an i-f
output stage, an a-f
amplifier,
and an a-f power output stage. The receiver
circuitry available
for double conversion does not in-
clude
the initial gate stage of the i-f amplifier used for
single conversion, but includes asecond mixer and a
second
heterodyne crystal-controlled osciIIator. The re-
ceiver self-contained
power supply system includes a
full-wave
power rectifier and voltage regulator, and a
full-wave bias rectifier.
1-14. For fixed-frequency crystal-controlled reception,
the variable-frequency first heterodyne osciIIator is re-
placed by afixed-frequency crystal-controIIed osciIIator.
This is accomplished when the "FREQ CONTROL" se-
lector switch (8, figure
1-2) is switched from its "VFO"
to one of its "XT ALS" positions. Each of the six
"XT ALS" positions is associated with acrystal which is
suited
to the frequency of the operational activity con-
templated.
The small plastic chart (9) is used to record
the applicable signal frequency for each of the crystals.
For crystal-controlled reception, the main dial is set to
the signal frequency, and tuning is accomplished through
use of the "/'::, FREQ" control (7). A slight tuning ad-
justment in the chosen setting of the "TUNING" con-
trol (15) is desirable to resonate the r-f section to the
signal.
3

Section 1
Paragraphs 1-15 to 1-22
T.O. 31R2-4-101-2
1-15. The frequency control unit crystals, per Specifi-
cation MIL-C-3098, should be purchased on special or-
der to Hammarlund Specification No. 31473. The oper-
ating frequency of each crystal for single-conversion use,
up to and including 7.4 me, is specified as the signal
frequency plus 455 kc; and for double-conversion use,
from 7.4 me to 12.0450 me, it is specified as the signal
frequency plus 3955 kc. For signal frequencies from
12.0450 to 54.0 me the third harmonic mode of oper-
ation of the crystal is used. The crystal frequency speci-
fied is
the signal frequency plus 3.955 me divided by
three. The allowable frequency tolerance of each crystal
is 0.005
percent of frequency.
1-16. When the "AVC/MAN" switch (11, figure 1-2)
is in the "A VC" position and the "RF GAIN" control
(12) is fully clockwise, the receiver front-panel dual-
scale meter provides an r-f indication of the relative
strength of the received signal in decibels from one
microvolt. The r-f indication is used for tuning when on
ave. When the spring-return "METER" switch (3) is
held depressed in its "AF" position, the lower scale of the
meter indicates the receiver audio output power level
in decibels from six milliwatts standard reference out-
put.
1-17. The receiver provides a-v-c action when the
"A VC/MAN" switch is in its "A VC" position. The re-
ceiver
gain maintained is dependent on the setting of
the "RF GAIN" control. For normal keyed carrier re-
ception, the receiver "BEAT OSc." control (10, figure
1-2) may be set to provide receiver single-tone output
at any pitch within the range of plus or minus three kc
from zero tone output. For frequency-shift reception, the
two-tone receiver output provided is dependent on the
setting chosen for the control and on the carrier
frequency-shift.
1-18. The receiver provides effective a-v-c action as
long as the rate of signal fading does not approach the
signal speeds used. Two different a-v-c networks are
provided. When the "MOD/CW" switch (13) is in the
"cw" position a long time-constant network is used; in
the "MOD" position, a short time-constant network is
used.
The "AVC" terminals (t, figure 1-3), when in-
terconnected between receivers in aspace diversity re-
ceiving system,
enable the receiver with the larger signal
input to control the gain of the receiver with the smaller
signal input.
1-19. The receiver "SELECTIVITY" switch (18, figure
1-2) provides achoice of anyone of six degrees of
receiver selectivity, the three narrower "SHARP" band-
widths being realized through use of acrystal filter
which forms part of the i-f section of the receiver. With
the "SELECTIVITY" switch in anyone of its "SHARP"
positions, the crystal filter "XT AI. PHASING" control
provides for attenuation of heterodyne interference, even
when the unwanted signal is closely adjacent to the de-
sired signal.
1-20. CONDENSED FACTUAL DATA.
1-21. TUBE COMPLEMENT. The tube complement of
the receiver is shown in table I. The table identifies each
of the 20 electron tubes by JAN-type designation, circuit
reference symbol and circuit function.
1-22. FUSE COMPLEMENT. The fuse complement of
the receiver (table II) consists of two fuses and a spare
for each. Each fuse is glass-enclosed, indicating, and com-
mercially available.
The %-ampere fuse is of the in-
stantaneous type and the 1.6-ampere fuse is of the slow-
blow time-delay type. The table identifies each fuse by
Bussman Manufacturing Company part number, ampere
rating, circuit reference symbol, and type.
JAN Type
Qty
5749/6BA6W
7
6C4
3
6AC7
1
6BE6
2
S726/6AL5/6097
3
12AU7
1
6V6GT
1
SR4GY
1
OA2
1
4
TABLE I. TUBE COMPLEMENT
Function
Amplifiers: r-f, i-f, b-f-o buffer
Oscillators:
variable frequency, 3.5-mc, bfo
Oscillator, fixed frequency
Mixers: first, second
Detector and ave; limiter and meter; bias
rectifier
Cathode follower and first audio
Audio power output
Rectifier
Voltage regulator
Reference Symbol
VI, V2, V7, V9, V1O, Vll,
V12
V4, V8, VB
V3
V5, V6
VI4A, B; VI5A, B; V20
V16
V17
V19
V18

T.O. 31R2-4-101-2
Section I
Paragraphs 1-23 to 1-31
TABLE II. FUSE COMPLEMENT
Sussman
Ampere
Reference
Part No.
Qty
Rating
Type
Symbol
AGC 3/8
2
3/8
Cartridge
F2
MDL 1-6/10
21.6
Cartridge
Fl
125V,
Fusetron
1-23. FREQUENCY RANGE AND STABILITY. The
six frequency bands of the receiver provide for continu-
ous reception
within the frequency range of 0.54 to 54.0
mc. Subsequent
to a15-minute warmup period, the re-
ceiver frequency
drift, as a percentage of the signal fre-
quency
tuned in, ranges from 0.001 to 0.01 percent.
This frequency stability approaches that provided by
the receiver
for fixed-frequency crystal-controlled recep-
tion,
within the frequency range of 0.75 mc to 54.0 me.
1-24. TUNING BAND RANGES. The tunable fre-
quency
range of each of the six frequency bands of the
receiver is shown in table III. The innermost scale of the
main tuning dial is that for the lowest frequency range.
The band numeral assigned each band is an arbitrary
designation.
1-25. OUTPUT CHARACTERISTICS. The maximum
undistorted power output of the receiver is two watts.
The receiver audio output terminals and the i-f output
connector are designed to match loads of 600 ohms and
70 ohms, respectively. An 8000-ohm headset is recom-
mended for use with the phones jack. When the audio
output is 500 milliwatts across a600-ohm load, the
phones output is 15 milliwatts; and with two microvolts
receiver
signal input, the i-f output to a70-ohm load is
a
minimum of 0.6 milliwatt.
1-26. SENSITIVITY. The m-c-w sensitivity of the re-
ceiver
to any signal frequency within its tuning range is
two microvolts or better, for asignal-plus-noise to noise
power ratio of ten to one at the receiver audio output
terminals. Similarly, the cow sensiti,vity of the receiver is
0.75 microvolt,
or better.
TABLE III. TUNING BAND RANGES
1-27. SELECTIVITY. The receiver selectivity or band-
pass characteristics provided for each of the six positions
of the selectivity switch are shown in figure 1-4.
1-28. FIDELITY. The audio and overall fidelity curves
for the receiver are shown in figure 1-5. The solid
curve indicates
the fidelity of the audio-frequency am-
plifier
with input applied between terminal 3 of the
"AUDIO GAIN" control (16, figure 1-2) and ground,
and with the "RF GAIN" control (12) at minimum. The
broken curve indicates the overall fidelity at 2.5 mc; with
AM. of 30 percent, "SELECTIVITY" switch (18) in the
13-kc position, and the "RF GAIN" control set for a
IO-mw reference-level
output. In each instance, the out-
put is measured across a600-ohm resistive load (the
"AUDIO GAIN" control set at maximum).
1-29. REJECTION RATIOS. The image rejection ratios
of the receiver at the high frequency end of each re-
ceiver
band are shown in table IV. The 455-kc i-f rejec-
tion ratio of the receiver is 69 db with the receiver
tuning mechanism set to tune in a600-kc signal. This
ratio, applicable to single conversion, improves with
frequency for bands 1, 2, and 3. The 3955-kc i-f rejection
ratio of the receiver, applicable to double conversion, is
a
minimum of 94 db with the receiver tuning mechanism
set to
tune in any signal within the frequency range of
bands 4, 5, and 6.
1-30. AUTOMATIC VOLUME CONTROL. The a-v-c
action
maintains the receiver output constant within 14
db when the input is increased from two to 200,000
microvolts.
1-31. LINE SUPPLY REQUIREMENTS. Asingle-
phase, 50-
to 60-cycle a-c power source within the volt-
age range of 90 to 270 volts is required to provide input
power to the receiver. Voltage taps on the primary wind-
ing of the receiver power transformer are provided for
line voltages below or above the usual U5-volt source.
For an a-c line voltage of 117 volts, the receiver current
drain is 1.25 amperes and its power consumption is
130 watts.
The maximum starting current is two amperes.
TABLE IV. IMAGE REJECTION RATIOS
Image Rejection
Ratio
Sand Voltage
Sand No.
Frequency Range
No. Frequency Ratio OS
10.54
to
1.35 mc 11.35 mc 60,000 95
21.35
to
3.45 mc 23.40 mc 10,000 80
33.45
to 7.40 mc 37.40 mc 4,000 72
47.40 to 14.80 mc 414.50 mc 300,000 109
514.80
to 29.70 mc 529.50 mc 50,000
94
629.70 to 54.00 mc 654.00 mc 5,000
74
5

Section IT.O.
31 R2-4-101-2
NUMBERS DENOTE SELECTIVITY SWITCH POSITIONS
'1,2 AND:3 NON CRYSTAL - 4,5 AND 6CRYSTAL
'I
15
2
10
:3
6 54
45 6
5 0 5
KC OFF RESONANCE
:3
10
2
15
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10
100
1000
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Figure J -4. Overall Selectivity Curves at Two Megacycles
6

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:::::>
"
z
10
".
W
IL.-
f-
.L
~
f-
15
:::::>
Cl.
f-
:::::>
20
0
25
40
100
T.O. 31R2-4-101-2
SOLID CURVE: A-F AMPLIFIER RESPONSE
DASHED CURVE: OVERALL RESPONSE
(SEE
TEXT)
1000
CYCLES PER SECOND
Figure 1-5. Audio and Overall Fidelity Curves
Section I
Paragraphs 1-32 to 1-44
"-
10,000
1-32. TEMPERATURE AND HUMIDITY. The re-
ceiver will perform satisfactorily in ambient tempera-
tures
ranging from O°C (32°F) to 60°C (140°F) at a
relative humidity
as high as 95 percent.
1-33. OPERATING AND ADJUSTMENT
CONTROLS.
1-34. The receiver operating and adjustment controls
are located
on the front panel (figure 1-2) and on the
rear apron (figure 1-3), respectively. The controls are
referred to below by
their front-panel and rear-apron
designations.
1-35. "SEND/REC". The "SEND/REC" switch (21, fig-
ure 1-2) is used to switch the receiver from its "REC"
(receive) condition to adisabled "SEND" condition in
the presence of a strong local carrier. When switched
back to
"REC", the receiver is ready for instant use.
1-36. "MOD/CW". The "MOD/CW" switch (13, fig-
ure 1-2) is used to control the beat frequency oscillator
and the a-v-c time-constant network. In the "CW" posi-
tion the bfo is turned on, and a long time constant is
used
for the ave. This position is used for suppressed-
carrier
and keyed-carrier reception, and also for
frequency-shift reception when the receiver audio output
is required for afrequency-shift converter, or the audio
output is desired for aural monitoring. The "MOD"
position is used for m-c-w reception. In this position
the bfo is turned off and a short time constant is used
for the avc.
1-37. "BAND CHANGE". The "BAND CHANGE"
control (17, figure 1-2) is used to select the desired
frequency band.
1-38. "TUNING". The "TUNING" control (15, fig-
ure
1-2) is used to tune in the signal.
1-39. "TUNING LOCK". The "TUNING LOCK" (14,
figure 1-2) is used to lock the tuning mechanism at
the tuning setting chosen.
1-40. "SELECTIVITY". The "SELECTIVITY" switch
(18, figure
1-2) provides achoice of "XT AL" (crystal)
and three "NON-XTAL" (noncrystal) positions of re-
ceiver selectivity.
The six positions provide selectivity
steps
ranging from a "SHARP" to a "BROAD" indica-
tion.
The "XT AL" switch positions provide bandwidths
of 0.2, 0.5, and 1.3 kc, and the "NON-XTAL" switch
positions
provide bandwidths of 3.0, 8.0, and 13.0 ke.
1-41. ~'XTAL PHASING". The "XTAL PHASING"
control (1, figure 1-2) is used to attenuate heterodyne
interference closely adjacent to
the desired signal. It
provides this function only when the "SELECTIVITY"
switch (18) is in one of its three "XT AL" positions.
1-42. "BEAT OSc.". The "BEAT OSc." control (10,
figure
1-2) is used to vary the frequency of the bfo, as
required for keyed-carrier and frequency-shift operation.
The pitch of the tone or tones is dependent on the set-
ting of the control. The control may be set on scale in
either direction from its "0" position. It provides a plus
and minus three-kc tone range. For suppressed-carrier
m-c-w reception,
the control, when set to its "0" posi-
tion, provides the b-f-o output as the 455-kc reinserted
carrier.
1-43. "RF GAIN". The "RF GAIN" control (12, fig-
ure 1-2) is used to switch the receiver on when turned
clockwise from its "OFF" position to a point where a
click is heard. Clockwise
rotation of the control increases
the r-f and i-f gain of the receiver. To prevent overload-
ing the receiver r-f and i-f sections in manual operation,
the
control is turned down somewhat from the maximum
position. The control is also turned down, when on avc,
to reduce
the sensitivity of the receiver during periods
when the signal is off and fading, so that the undesirable
noise
output may be reduced.
1-44. "AVC/MAN". The "AVCjMAN" switch (11,
figure
1-2) is used to switch from automatic to manual
control of the receiver r-f and i-f gain. The "RF GAIN"
control (12) is operative in both positions of the "A VC/
MAN" switch.
7

T.O. 31R2-4-101-2
Section I
Paragraphs 1-45 to 1-52
1-45. "METER". The spring-return "METER" switch
(3, figure
1-2) is associated with the tuning meter (2).
In its normal "RF" position, the switch provides acali-
brated r-f meter indication if the "RF GAIN" control
(12) is fully clockwise. When the switch is held in its
depressed
"AF" position, it provides acalibrated a-f
meter indication.
To avoid meter damage, set the "AUDIO
GAIN" control (16, figure 1-2) fully coun-
terclockwise,
then depress the meter switch,
and then slowly increase the audio level to the
desired meter scale indication.
1-46. "AUDIO GAIN". The "AUDIO GAIN" control
(16, figure 1-2) is used to adjust the receiver audio
output to acomfortable level. The receiver audio output
is adequate to operate any recording equipment care-
fully,
but the receiver controls should be adjusted to
provide undistorted output.
1-47."LIMITER/OFF". The "LIMITER/OFF" switch
(19, figure 1-2) controls anoise-limiting circuit. In the
"LIMITER" position the limiter is operative, in the
"OFF" position it is not. The switch should be kept in
the "OFF" position, unless pulse-type noise is interfer-
ing with reception.
1-48. "FREQ CONTROL". The "FREQ CONTROL"
switch (8, figure 1-2) controls the selection of the
variable-frequency oscillator for variable-frequency op-
eration,
or· the crystal-controlled oscillator for fixed-
channel
operation on any of six preselected channels.
In the "VFO" position, the continuously variable oscil-
lator is placed in operation. In any of the six "XT ALS"
positions, the crystal associated with the switch position
is connected
to the crystal-controlled oscillator, and the
crystal oscillator is placed in operation.
1-49. "D,. FREQ". The "D,. FREQ" control (7, figure
1-2) is used to tune in the signal when the fixed-
frequency crystal-controlled first heterodyne oscillator
is
being used. The control provides a slight adjustment
in the frequency of the oscillator, necessitated by the
0.005-percent frequency tolerance inherent in each crys-
tal used. The panel markings designate an arbitrary fre-
quency scale
for the control setting. Clockwise rotation
produces arelatively lower oscillator frequency.
1-50. "METER AD] RF'. The "METER AD] RF" con-
trol (5, figure 1-3) is used to calibrate the r-f scale of
the tuning meter (2, figure 1-2). With a10-microvolt
input signal and the "RF GAIN" control (12) fully on
the "METER AD] RF" control is set for an r-f meter
scale reading of +20 db.
1-51. "METER AD] AF". The "METER AD] AF" con-
trol (7, figure 1-3) is used to calibrate the a-f scale of
the tuning meter (2, figure 1-2). With a600-ohm re-
sistive
load connected to the "AUDIO OUTPUT" termi-
nals (8) and 1.9 volts or six miIIiwatts of audio output,
the "METER AD] AF" control is set to provide azero-
db a-f meter scale reading.
1-52. "BFO IN]". The "BFO IN]" control (4, figure
1-3) provides the means for adjusting the level of the
b-f-o injection voltage applied from the buffer stage to
the detector stage.
8

T.O. 31R2-4-101-2
SECTION II
TEST EQUIPMENT AND SPECIAl TOOLS
Section II
Paragraphs 2-1 to 2-7
2-1. TEST EQUIPMENT.
2-2. The test equipment required for testing, servicing,
and aligning the radio receiver is listed in table V. No
special test equipment is required.
Figure 2-1. Special Pliers
2-3. SPECIAL TOOLS.
2-4. The special tools procured for the maintenance
of the radio receiver are listed in table VI.
2-5. CABLE FABRICATION.
2-6. ANTENNA CABLE. The antenna cable is used to
connect the signal generator to the antenna input con-
nector of the receiver for test or alignment purposes. It
comprises the parts shown in figure 2-2.
2-7. CATHODE FOLLOWER CABLE. The cathode
follower cable is used to connect the output meter to the
i-f output connector for test purposes. It comprises the
parts shown in figure 2-3.
TABLE V. TEST EQUIPMENT REQUIRED FOR MAINTENANCE
AN Type
Name Designation
Electronic Multimeter ME-74jU
Electronic Multimeter
ANjUSM-34
Audio Oscillator
TS-382AjU
RF Signal Generator Set
ANjURM-25
RF Signal Generator Set
ANjURM-26
Signal Generator
TS-447jU
.
Cathode Ray Oscilloscope
OS-9jU
Tube Tester
ANjUSM-31
Alternate
ME-6AjU
ME-25AjU
Hewlett-Packard 200AB
Precision E-200-C
Precision E-200-C
Hickok Model 188
DuMont Model 208
TV-3AjU
Use
A-c voltmeter and db meter
(useful to 500 kc)
General purpose vtvm and
ohmmeter
Audio response tests
Alignment and testing, lO-kc
to 50-mc A-M signal gen-
erator
Alignment and testing, 3-mc
to above 54-mc A-M signal
generator
Alignment and testing, sweep
generator covering 445 kc
and 3955 kc
Used with sweep generator
for alignment purposes
Tube checking
TABLE VI. SPECIAL TOOLS REQUIRED FOR MAINTENANCE
Figure
2-1
Hammarlund
Part No.
T8222
Name
Pliers, special
Application
Removal and replacement of flat spring
for r-f tuners
9

Section II
T.O. 31R2-4-101-2
PL-259 RG-59/U 100 OHM
~a2 ~ F==9
LANTENNA INPUT CONNECTOR TO SIGNAL GENERAT~
Figure 2-2. Antenna Cable
PL-259~ RG-59/U,,\
(APPROX 20 IN.
LONG)
[0
.
,_1~3
Ll FOUTPUT
CONNECTOR
10
Figure 2-3. Cathode-follower Cable

T.O. 31R2-4-101-2
SECTION III
PREPARATION FOR USE AND RESHIPMENT
Section III
Paragraphs 3-1 to 3-9
3-1. PREPARATION FOR USE.
3-2. UNCASING.
3-3. The radio receiver is packed for shipment at the
factory. An outer wooden case encloses a carton which
contains the receiver proper and a bag containing the
receiver cable plug connectors, which are removed from
the receiver for shipment. Unpack the equipment as fol-
lows:
a. Cut the steel straps, close to the wooden case cover,
and fold them back.
b. Remove the cover.
c. Remove the carton containing the receiver and plug
connectors from the case.
d. Remove the
waterproof tape from the waterproof
covering wrapped around the carton; remove the water-
proof paper wrapper and open the carton.
e. Remove
the wood frame from the carton; also the
accordion-folded corrugated interiors comprising two
side pieces, one front, one back, and one top. Remove
the bag containing the receiver plug connectors.
f. Remove the receiver
and place it out of the way, in
aconvenient place near its final location.
g. Remove
the receiver plug connectors from the outer
cloth, inner paper bag, and plastic bags.
h.
Put all packing material in the wooden case and
store.
3-4. SETTING UP RECEIVER.
3-5. PRIMARY TAP USED. When shipped, the radio
receiver power transformer primary tap is connected to
operate from a50- to 60-cycle, 117-volt a-c source. Ta-
ble V II shows the a-c source voltage rating of each pri-
mary tap, identified by the numerical . designation as-
signed it on the bottom of the power transformer.
TABLE VII. POWER TRANSFORMER TAP
VOLTAGE RATINGS
[ CAUTION
Choose the power transformer primary tap
whose voltage rating is in closest agreement
with the a-c source voltage.
3-6. PLUG CONNECTOR ASSEMBLIES. Each plug
connector assembly removed from the receiver for ship-
ment is listed in table VIII. As it is unpacked, connect
each
plug to the receiver.
3-7. PREPARATION FOR RESHIPMENT
OR STORAGE.
3-8. When the radio receiver is to be reshipped or to be
stored subsequent to use, remove the frequency control
unit crystals, as instructed in paragraph 5-15, and re-
move
the plug connector assemblies listed in table VIII.
Fully mesh the eight-section, four-gang variable air ca-
pacitor and then pack the receiver as described in para-
graph 3-9.
3-9.
To pack the receiver, proceed as follows:
a. Open the folded receiver carton and tape all edges
with three-inch gummed kraft paper tape.
b.
Accordion-fold the ends of a corrugated cardboard
bottom for the carton, to act as a spring-board bottom
for the receiver. Place it in the carton with the accordion
folds downward.
c. Place the receiver in the carton and cover the re-
ceiver
panel with wrapping paper.
d. Put into the carton, around the receiver, accordion-
folded
corrugated interiors, comprising two side pieces,
one front, one back, and one top, with the accordion
folds against
the walls of the carton; also put in one
wood frame to act as a carton spacer.
TABLE VIII. PLUG CONNECTOR ASSEMBLIES
REMOVED FROM RECEIVER FOR SHIPMENT
Tap No. Voltage Rating
295
3105
4117
5130
6190
7210
8234
9260
Reference
Symbol
P2
P3
P4
Government Type
Designation
Antenna Input Plug
UG-102/U
Antenna Adapter
Connector
UG-104/U
PL-259
Connects To
Antenna adapter
connector P3
"ANT" input jack
(]1, figure 5-4)
"IF OUTPUT"
connector
(6, figure 1-3)
11

Section III
T.O.31 R2-4-1 01-2
e. Put the receiver plug connectors listed in table
VIII into the plastic bags, press the bags to exhaust as
much air as possible, and heat-seal. Place the plastic bags
into the paper and cloth bags, and place in the carton at
the side of the receiver.
f.
Complete the taping of the carton, using the three-
inch tape.
12
g. Wrap the carton in waterproof paper and seal all
folds with three-inch waterproof tape.
h.
Put the waterproof-wrapped carton into the
wooden case.
i.
Nail the cover on the wooden case and put two
steel straps around the case.
j. Stencil aU markings on the end of the case and
affix an address label on the side.

T.O. 31R2-4-101-2
SECTION IV
THEORY OF OPERATION
Section IV
Paragraphs 4-1 to 4-11
4-1. GENERAL SYSTEM OPERATION.
4-2. The radio receiver is designed for use in single- or
multi-receiver military installations. Where required, two
or more receivers may be used in aspace-diversity ar-
rangement. In this system, each receiver is connected to a
separate
antenna and the antennas arranged in proper
space relationship to each other. The receivers may be
interconnected to provide a common a-v-c system and/or
common audio output, as required.
4-3. The receiving system provides for reception of
A-M, COw, or frequency-shift signals. Receiver output
may be in the form of audio signals, available at the
"PHONES" jack (20, figure 1-2) or at the "AUDIO
OUTPUT" terminals (8, figure 1-3); doc signals, avail-
able
at the "DIODE OUTPUT" terminals (2); or 455-kc
signals, available
at the "IF OUTPUT" connector (6).
4-4. RECEIVING SYSTEM BLOCK DIAGRAM.
4-5. Atypical space-diversity system for the reception
of frequency-shift teletype signals is illustrated in block
form in figure 4-1. Space-diversity systems make use
of the fact that signals induced in antennas five to ten
wavelengths apart fade separately. Each receiver has a
separate
antenna and the two antennas are suitably
spaced
in relation to each other. The output signal, in
this instance, is supplied from the "IF OUTPUT" con-
nectors
of both receivers. The a-v-c systems of the two
receivers are interconnected at the "A VC" terminals (3,
figure 1-3) on- the rear apron.
4-6. In space-diversity operation, the signals induced
in the two antennas vary in intensity, depending upon
propagation characteristics. In any event, the receiver
with the stronger input signal develops the larger a-v-c
voltage and supplies the output signal to the frequency-
shift converter equipment. Since the two a-v-c systems
are interconnected, the
large a-v-c voltage developed in
the receiver with the stronger input signal reduces the
gain of the other receiver to reduce its noise output.
When conditions reverse, the action of the two receivers
reverses also,
and the output signal is supplied by the
second receiver. The frequency-shift converter equipment
converts the i-f signal to a doc signal suitable for operat-
ing ateletype-writer unit.
4-7. For other possible receiving systems, refer to the
handbook of operation instructions for the radio re-
ceiver.
4-8. RECEIVER FUNCTIONAL OPERATION.
4-9. RECEIVER BLOCK DIAGRAM. Figure 4-2
shows in block form the relationship existing among
the internal circuits of the receiver. Indicated in each
block are the tube type and schematic symbol designa-
tion of the electron tube associated with each stage. The
receiver is a superheterodyne type using single conver-
sion
on frequencies below 7.4 mc and double conversion
on frequencies above 7.4 mc. The antenna input circuit
is designed
for a balanced doublet or asingle-wire an-
tenna system.
4-10. The signal voltage induced into the antenna cir-
cuit is
applied to atwo-stage, tuned r-f amplifier, com-
prising tubes VI and V2 and their associated circuitry.
A
rotary turret assembly is employed to change bands
by inserting the proper coil assemblies into the r-f am-
plifier circuits. The two tuned stages of r-f amplification
provide a high degree of image rejection and selectivity,
and a high signal-to-noise ratio. The gain of the r-f
amplifiers is established by the setting of the "RF GAIN"
control (12, figure 1-2) in manual operation and, ad-
ditionally, by
the a-v-c voltage developed by the incom-
ing signal when a-v-c operation is employed. The signal
selected and amplified in the r-f amplifier circuits is
applied to the frequency conversion section of the re-
ceiver.
4-11. The first frequency conversion section of the re-
ceiver comprises
the first mixer stage and either a
crystal-controlled, fixed-frequency
heterodyne oscillator
stage
or avariable-frequency heterodyne oscillator stage.
The selection of the heterodyne oscillator circuit is ac-
complished by means
of the "FREQ CONTROL" selec-
tor switch (8, figure 1-2). When the switch is rotated
to the "VFO" position, avariable-frequency heterodyne
oscillator is selected, and its output applied to the injec-
tion grid of first mixer tube V5. Variable-frequency os-
cillator tube V4, with its associated circuitry, comprises
an Armstrong-type oscillator circuit on the lower three
bands of the receiver and aColpitts-type circuit on the
three higher bands. The rotary turret assembly inserts
the proper oscillator tank elements into the circuit for
each band. When the "FREQ CONTROL" selector
switch is
rotated to one of its six "XT ALS" positions,
the variable-frequency oscillator is disabled and afixed-
frequency, crystal-controlled
heterodyne oscillator is
placed
in operation. Tube V3 an<;l its associated cir-
cuitry comprise an electron-coupled Pierce-type oscillator
circuit whose frequency is established by
the crystal in-
serted
into the selected crystal socket. On the three lower
receiver bands, the heterodyne oscillators operate 455
kc above
the frequency of the incoming signal; on the
three higher bands of the receiver, the oscillator fre-
quency is 3955 kc above
the signal frequency. The incom-
ing signal and the output of the heterodyne oscillator
are applied to pentagrid mixer tube V5 and heterodyne-
detected
in the first mixer stage. The output of the stage
is
either 455 kc or 3955 kc, depending upon the fre-
quency
band selected. On the three lower frequency
13

Section IV
Paragraphs 4-12 to 4-13
T.O. 31R2-4-101-2
I\v PHYSICALLY\V
SPACED
~5TOIO-
WAVELENGTHS
APART
ANT
SP-600- JX - 21 I
~AVC jof
IF
- G
10 oIOUTPUT
I I
1A A AJ
600~OHMS FREQUENCY
2WATTS SHIFT
0-
f--
TELETYPEWRITER
CONVERTER UNIT
ANT
SP - 600-JX - 21 I
'-oAVC :()o
_ G
19
<j>
IF OUTPUT
I I
IA
600-0HMS
2 WATTS
Figure 4-1. Space-diversity Reception of Frequency-shift Signals, System Block Diagram
bands, the 455-kc output signal is applied to tube V7
in the gate circuit; aswitch ganged to the "BAND
CHANGE" control (17, figure 1-2) applies d-c power
to the gate tube and disables the 3.5-mc crystal oscil-
lator and the second mixer; and the 455-kc i-f signal
passes
through the gate circuit and is applied to the i-f
amplifier section.
The gate circuit provides some i-f
amplification
but its primary purpose is to provide a
signal
path for the 455-kc i-f signal.
4-12. On the three upper frequency bands of the re-
ceiver, signal conversion to an if.
of 455 kc is unable to
provide suitable image rejection in the r-f section of the
receiver. The heterodyne oscillators are therefore de-
signed to operate 3955 kc above the frequency of the
incoming signal. When the two frequencies are
heterodyne-detected
in the first mixer stage, a3955-kc if.
results. Before application to
the i-f amplifiers, the sig-
nal must be converted to the 455-kc frequency to which
the i-f circuits are tuned. This second frequency con-
version is accomplished
in the second mixer circuit. A
14
switch ganged to the "BAND CHANGE" control dis-
ables
the 455-kc i-f gate circuit and applies power to the
3.5-mc crystal oscillator tube V8 and to second mixer
tube V6. The 3.5-mc triode crystal oscillator circuit be-
comes
operational and provides asignal for the injection
grid of the second mixer tube. The 3955-kc signal from
the first mixer is applied to the signal grid of the same
tube.
The two frequencies are heterodyne-detected in
the second mixer circuit and an if. of 455 kc results.
Through use of the double-conversion system, the ad-
vantages
of high gain obtainable with a low if., and
good image rejection obtainable with a. high if. are both
realized.
4-13. The 455-kc signal from the second mixer stage,
or from the gate stage, is applied to acrystal filter cir-
cuit.
The front-panel "SELECTIVITY" switch (18, fig-
ure 1-2) provides receiver bandwidths of 0.2 kc, 0.5 kc,
1.3 kc, 3kc, 8kc,
and 13 kc, with the crystal filter circuit
providing the three sharp degrees of selectivity. The
crystal, in conjunction with the "XTAL PHASING" con-
trol (1), provides extreme selectivity for the attenuation
of closely adjacent interfering signals.