TM 11-5820-590-12-1
TECHNICAL MANUAL
OPERATOR'S AND ORGANIZATIONAL MAINTENANCE MANUAL
(INCLUDING REPAIR PARTS AND SPECIAL TOOLS LISTS)
RADIO SETS AN/PRC-74B (NSN 5820-00-935-0030) AND
AN/PRC-74C (NSN 5820-00-177-1641); AND
POWER SUPPLIES PP-4514/PRC-74 (NSN 5820-00-942-0821)
AND PP-4514A/PRC-74 (NSN 5820-00-177-4581); AND
BATTERY BOXES CY-6121/PRC-74 (NSN 5820-00-908-3127),
AND CY-6314/PRC-74
AND CY-6314A/PRC-74 (NSN 5820-00-156-3934)
This copy is a reprint which includes current pages from
Changes 1 through 7. Title was changed to read as shown
above by C 6.
HEADQUARTERS, DEPARTMENT OF THE ARMY
MARCH 1967
TM 11-5820-590-12-1
C 8
CHANGE HEADQUARTERS
No. 8 DEPARTMENT OF THE ARMY
Washington, DC, 15 February 1988
Operator's and Organizational
Maintenance Manual
(Including Repair Parts and Special Tools List)
RADIO SETS AN/PRC-74B (NSN 5820-00-935-0030)
AND AN/PRC-74C (NSN 5820-00-177-1641)
POWER SUPPLIES PP-4514/PRC-74 (NSN 5820-00-942-0821)
AND PP-4514A/PRC-74 (NSN 5820-00-177-4581)
BATTERY BOXES CY-6121/PRC-74 (NSN 5820-00-908-3127)
CY-6314/PRC-74 (NSN 5820-00-935-0382)
AND CY-6341A/PRC-74 (NSN 5820-00-156-3934)
TM 11-5820-590-12-1, 3 March 1967, is changed as follows:
1. Remove old pages and insert new pages as indicated below. New or changed material is indicated by a vertical
bar in the margin of the page. Added or revised illustrations are indicated by a vertical bar adjacent to the
identification number.
Remove pages Insert pages
G and H ................................................... G and H
i and ii...................................................... i and ii
1-1 through 1-4......................................... 1-1 through 1-4
3-4.1 and 3-4.2......................................... 3-4.1 and 3-4.2
4-1 through 4-4......................................... 4-1 through 4-4
6-1 and 6-2............................................... 6-1 and 6-2
A-1........................................................... A-1/(A-2 blank)
2. File this change sheet in the front of the publication for reference purposes.
Distribution authorized to the Department of defense and DOD
contractors only for official use or for administration or
operational purposes. This determination was made on 3
November 1937. Other requests for this document will be
referred to Commander, US Any Communications-Electronics
Command and Fort Monmouth, ATTN: AMSEL-ME-P, Fort
Monmouth, NJ 07703-5000.
DESTRUCTION NOTICE-Destroy By any method that will
prevent disclosure of contents or reconstruction of the
document.
By Order of the Secretary of the Army:
General, United States Army
OFFICIAL:
R. L. DILWORTH
Brigadier General, United States Army
The Adjutant General
DISTRIBUTION:
To be distributed in accordance with DA Form 12-51 literature requirements for
AN/PRC-74, A, B, C.
CARL E. VUONO
Chief of Staff
TM 11-5820-590-12-1
C7
CHANGE HEADQUARTERS
DEPARTMENT OF THE ARMY
NO.7 WASHINGTON DC, 1 October 1981
Operator's and Organizational
Maintenance Manual
(Including Repair Parts and Special Tools Lists)
RADIO SETS AN/PRC 74B (NSN 5280-00-935-0030) AND
AN/PRC -74C (NSN 5820-00-177-1641): AND
POWER SUPPLIES PP-4514/PRC-74 (NSN 5820-00-942-0821) AND
PP 4514A/PRC 74 (NSN 5820-00-177-4581); AND
BATTERY BOXES CY 6121/PRC 74 (NSN 5820-00-908-3127), AND
CY 6314/PRC 74
AND CY 6314A/PRC 74 (NSN 5820-00-156-3934)
TM 11-5820-590-12-1, 3 March 1967, is changed as follows:
1. New or changed material is indicated by a vertical bar in the margin of the page.
2. Remove and insert pages as indicated in the page list below:
Remove Insert
i and ii ................................................................... A through H
iii and iv................................................................... i through iii
1-1 and 1-2 ......................................................................... 1-1
3-3 and 3-4 ............................................................3-3 and 3-4
4-1 and 4-2 ............................................................4-1 and 4-2
None............................3 2028-2’s w/Sample (back of Manual)
3. File this change sheet in the front of the manual for reference purposes.
By Order of the Secretary of the Army:
E. C. MEYER
General, United States Army
Official: Chief of Staff
ROBERT M. JOYCE
Brigadier General, United States Army
The Adjutant General
DISTRIBUTION:
To be distributed in accordance with DA Form 12-51, Operator TM Literature requirements for
AN/PRC-74.
TM 11-5820-590-12-1
WARNING
AVOID R. F. BURNS
Do not touch the antenna when the radio set is being tuned or transmitting.
WARNING
DANGEROUS VOLTAGES EXIST IN THIS EQUIPMENT
Be careful when working on universal power supply circuits or on ac line connections.
WARNING
DANGEROUS CHEMICALS ARE USED IN NICKEL-CADMIUM BATTERIES
The electrolyte used in nickel-cadmium batteries contains potassium hydroxide (KOH), which is a caustic
chemical agent. Serious and deep burns of body tissue will result if the electrolyte comes in contact with the eyes
or any part of the body. Use rubber gloves, rubber apron, and protective goggles when handling the electrolyte. If
accidental contact with the electrolyte is made, use ONLY clean water and immediately (seconds count) flush
contaminated areas. Continue flushing with large quantities of clean water for at least 15 minutes. Seek medical
attention without delay.
WARNING
EXPLOSIVE GASES ARE GENERATED BY NlCKEL-CADMIUM BATTERIES
Hydrogen and oxygen gases are generated in explosive proportions while the nickel-cadmium battery is being
charged. Charge the nickel-cadmium battery in a well-ventilated area to reduce concentrations of explosive gases.
Turn off the battery charger before connecting or disconnecting the nickel-cadmium battery to prevent arcing. Do
not use matches or an open flame in the charging area. Arcs, flumes, or sparks in the charging area will ignite the
gases and cause an explosion. The battery box cover must be removed and the battery case vent plug (if used)
must be open when charging.
WARNING
Remove all jewelry and wristwatches when working on batteries. Be extremely careful when using metal tools.
WARNING
Operator and maintenance personnel should be familiar with the requirements of TB SIG 291 before attempting
installation or operation of equipment covered in this manual. Failure to follow requirements of TB SIG 291 could
result in injury or DEATH.
CAUTION
Do not use the whip antenna at 3.5 MHz or below. Use the components of Antenna Kit MK-911A/PRC-74.
CAUTION
Do not operate the radio set with one BA-4386/U. Use two BA-4386/U's in parallel at all times.
Change 7 A
TM 11-5820-590-12-1
CONDENSED OPERATING INSTRUCTIONS
FOR RADIO SET AN/PRC-74B
Receive Mode
a. Attach whip antenna mounting bracket to receiver-transmitter
b. Install whip antenna and adjust to desired frequency range.
c. Attach lead wire from whip antenna to front panel ANT terminal.
d. Connect headset to either front panel AUDIO jack.
e. The numbers (1) through (8) below are the same as the numbers on the diagram.
(1) Set front panel MC, 100 KC, 10 KC, and 1 KC selector knobs to the desired frequency.
(2) Turn OFF-ON-TUNE switch to ON position.
(3) Set RF GAIN control to maximum and adjust PEAK NOISE control for a definite, noticeable increase in
noise heard in the headset.
(4) Adjust ANT LOAD and ANT TUNE controls for maximum noise heard in headset.
(5) Press in CLARIFY/PUSH TO CALIBRATE knob and adjust so that a zero beat condition is observed in
the headset
(6) Release the CLARIFY/PUSH TO CALIBRATE knob and reset the pointer to midscale.
(7) Set RF GAIN control for desired volume of received signal.
(8) Adjust CLARIFY knob so that quality of received voice signals is natural.
Transmit Mode
f. Perform steps outlined above, do not perform steps (7) and (8) if no received signal is present.
g. Connect either microphone or key (depending on mode of operation desired) to the remaining audio jack.
h. The numbers (9) through (11) below are the same as the numbers on the diagram.
(9) Turn OFF-ON-TUNE switch to the TUNE position and listen for tone in headset.
(10) Adjust ANT TUNE knob to mid position. Adjust ANT LOAD knob until a maximum reading is obtained
on ANT IND meter. Adjust ANT TUNE knob until a maximum reading is obtained on ANT IND meter.
(11) Release OFF-ON-TUNE knob and allow to return to ON position.
Note. Repeat-step h each time transmitting frequency is changed.
i. Press microphone button and speak directly into the microphone.
TM5820-590-12-1-C1-1
Change 7 B
CONDENSED OPERATING INSTRUCTIONS
FOR RADIO SET AN/PRC-74C
Receive Mode
a. Attach whip antenna mounting bracket to receiver-transmitter.
b. Install whip antenna and adjust to desired frequency range.
c. Attach lead wire from whip antenna to front panel ANT terminal.
d. Connect headset to either front panel AUDIO jack.
e. The numbers (1) through (8) below are the same as the numbers on the diagram.
(1) Set front panel MHz, 100 KHz, 10 KHz, and 1 KHz selector knobs to the desired frequency.
(2) Turn OFF-ON-TUNE switch to ON position.
(3) Set RF GAIN control to maximum and adjust PEAK NOISE control for a definite, noticeable increase in
noise heard in the headset.
(4) Set ANT TUNE to mid range and ANT LOAD for maximum noise heard in headset.
(5) Press in CLARIFY/PUSH TO CALIBRATE knob and adjust so that a zero beat condition is observed in
the headset.
(6) Release the CLARIFY/PUSH TO CALIBRATE knob and reset the pointer to midscale.
(7) Set RF GAIN control for desired volume of received signal.
(8) Adjust CLARIFY knob so that quality of received voice signals in natural.
C 2, TM 11-5820-590-12-1
Transmit Mode
f. Perform steps outlined above, do not perform steps (7) and (8) if no received signal is present.
g. Connect either microphone or key (depending on mode of operation desired) to the remaining audio jack.
h. The numbers (9) through (11) below are the same as the numbers on the diagram.
(9) Turn OFF-ON-TUNE switch to the TUNE position and listen for tone in headset.
(10) Adjust ANT TUNE knob to mid position. Adjust ANT LOAD knob until a maximum reading is obtained on
ANT IND meter. Adjust ANT TUNE knob until a maximum reading is obtained on ANT IND meter.
(11) Release OFF-ON-TUNE knob and allow to return to ON position.
Note. Repeat-step h each time transmitting frequency is changed.
i. Press microphone button and speak directly into the microphone.
TM5820-590-12-1-C1-1
C
TM 11-5820-590-12-1
5
1
2
3
4
SAFETY STEPS TO FOLLOW IF SOMEONE
IS THE VICTIM OF ELECTRICAL SHOCK
DO NOT TRY TO PULL OR GRAB THE INDIVIDUAL
IF POSSIBLE, TURN OFF THE ELECTRICAL POWER
IF YOU CANNOT TURN OFF THE ELECTRICAL
POWER, PULL, PUSH, OR LIFT THE PERSON TO
SAFETY USING A WOODEN POLE OR A ROPE OR
SOME OTHER INSULATING MATERIAL
SEND FOR HELP AS SOON AS POSSIBLE
5
AFTER THE INJURED PERSON IS FREE OF
CONTACT WITH THE SOURCE OF ELECTRICAL
SHOCK, MOVE THE PERSON A SHORT DISTANCE
AWAY AND IMMEDIATELY START ARTIFICIAL
RESUSCITATION
Change 7 D
TM 11-5820-590-12-1
FIXED OPERATION WITH LONG RANGE ANTENNAS
WARNING
TELESCOPING TYPICAL TOWER EXTENDD RANGE DOUBLET ANTEMMA
ANTENNA MAST ANTENNA
NEVER ERECT THESE LONG RANGE ANTENNAS DIRECTLY UNDER POWERLINES.
IF YOU MUST ERECT THESE LONG RANGE ANTENNAS NEAR POWERLINES, POWERLINE
POLES OR TOWERS, OR BUILDINGS WITH OVERHEAD POWERLINE CONNECTIONS. NEVER
PUT THE ANTENNA CLOSER THAN TWO TIMES THE ANTENNA HEIGHT FROM THE BASE OF THE
POWERLINE, POLE, TOWER, OR BUILDINGS.
NEVER ATTEMPT TO ERECT ANY LONG RANGE ANTENNA WITHOUT A FULL TEAM.
BEFORE ERECTING ANY LONG RANGE ANTENNA, INSPECT ALL THE PARTS MAKING UP THE
ANTENNA KIT. DO NOT ERECT THE ANTENNA IF ANY PARTS ARE MISSING OR DAMAGED.
DO AS MUCH OF THE ASSEMBLY WORK AS POSSIBLE ON THE GROUND.
WHEN ERECTING THE ANTENNA, ALLOW ONLY TEAM PERSONNEL IN THE ERECTION AREA.
MAKE SURE THAT THE AREA FOR THE ANCHORS IS FIRM. IF THE GROUND IS MARSHY OR
SANDY, GET SPECIFIC INSTRUCTIONS FROM YOUR CREW CHIEF OR SUPERVISOR ON HOW TO
REINFORCE THE ANCHORS.
WHEN SELECTING LOCATIONS FOR ANCHORS, AVOID TRAVELED AREAS AND ROADS. IF YOU
CAN NOT AVOID THESE AREAS, GET SPECIFIC INSTRUCTIONS FROM YOUR CREW CHIEF OR
SUPERVISOR AS TO WHAT CLEARANCE YOUR GUY WIRES AND ROPES MUST HAVE OVER
TRAVELED AREAS AND ROAD.
CLEARLY MARK ALL GUY WIRES AND ROPES WITH THE WARNING FLAGS SUPPLIED BY YOUR
UNIT. IN AN EMERGENCY, USE STRIPS OF WHITE CLOTH AS WARNING STREAMERS.
IF YOU SUSPECT THAT POWERLINES HAVE MADE ACCIDENTAL CONTACT WITH YOUR
ANTENNA, STOP OPERATING, ROPE OFF THE ANTENNA AREA, AND NOTIFY YOUR SUPERIORS.
IF THE WEATHER IN YOUR AREA CAN CAUSE ICE TO FORM ON YOUR LONG RANGE ANTENNA
AND ITS GUY WIRES AND ROPES, ADD EXTRA GUYS TO SUPPORT THE SYSTEM. ROPE OFF
THE AREA AND POST IT WITH WARNING SIGNS LIKE "BEWARE OF FALLING ICE”.
DO NOT TRY TO ERECT ANY ANTENNA DURING AN ELECTRICAL STORM.
KEEP A SHARP EYE ON YOUR ANCHORS AND GUYS. CHECK THEM DAILY AND IMMEDIATELY
BEFORE AND AFTER BAD WEATHER.
Change 7 E
TM 11-5820-590-12-1
WARNING
SERIOUS INJURY OR EVEN DEATH CAN HAPPEN IF THE FOLLOWING ARE NOT
CAREFULLY OBSERVED WHEN INSTALLING AND USING THE ANTENNAS USED WITH
YOUR RADIO SETS
DO NOT STOP YOUR VEHICLE UNDER POWERLINES.
• IF POSSIBLE, TRY TO MAINTAIN MOBILE COMMUNICATIONS WITH YOUR ANTENNA(S) TIED DOWN.
• MAKE SURE AN ANTENNA TIP CAP IS SECURELY TAPED ON THE END OF EACH WHIP ANTENNA.
• DO NOT LEAN ACROSS OR TOUCH A WHIP ANTENNA WHILE THE TRANSMITTER IS ON.
• DURING CROSS-COUNTRY OPERATION, DO NOT ALLOW ANYONE TO STICK AN ARM, LEG OR
WEAPON OVER THE SIDES OF THE VEHICLE. IF YOUR ANTENNA ACCIDENTALLY TOUCHES A
POWERLINE AND A LEG, ARM, OR WEAPON CONTACTS THE DAMP BUSH OR THE GROUND, A
SERIOUS OR FATAL ACCIDENT CAN HAPPEN.
• IF YOU ARE NOT SURE THAT AN ANTENNA ON YOUR VEHICLE WILL CLEAR A POWERLINE, STOP
BEFORE YOU GET CLOSE TO THE POWERLINE AND EITHER CAREFULLY TIE DOWN THE ANTENNA
OR REMOVE ANTENNA SECTIONS TO MAKE SURE THAT YOU CAN SAFELY DRIVE UNDER THE
POWERLINE.
Change 7 F
TM 11-5820-590-12-1
WARNING
Remove the magnesium battery from Battery Box CY-6314( )/PRC-74 when the RT-794/PRC is not
being used. This is required to insure that hydrogen gas (a by-product of Magnesium Battery, BA-4386/U Discharge
Action) does not accumulate. Personnel may be injured and equipment damaged if the gas explodes.
WARNING
You can tell the difference between Magnesium Battery, BA-4386, and Lithium Battery, BA-5598, by looking at their
size. The Lithium Battery is half the size (smaller than) of the Magnesium Battery
WARNING
P P-4514/PRC-74
GROUND THE INSTRUMENT
To minimize shock hazard, the instrument chassis and cabinet must be connected to an electrical ground. The
instrument is equipped with a three conductor ac power cable. The power cable must either be plugged into an
approved three contact electrical outlet or used with a three contact to two contact adapter with the ground wire
(green) firmly connected to an electrical ground (safety ground) at the power outlet. The power jack and mating plug
of the power cable must meet International Electrotechnical Commission (IEC) safety standards.
WARNING
DO not attempt internal service or adjustment unless another person, capable of rendering first aid and
resuscitation, is present.
WARNING
SAFETY PRECAUTION
A periodic review of safety precautions in TB-385-4, Safety Precautions for Maintenance of Electrical/Electronic
Equipment, is recommended. When the equipment is operated with covers removed, DO NOT TOUCH exposed
connections or components. MAKE CERTAIN you are not grounded when making connections or adjusting
components inside the test instrument.
WARNING
A lithium-sulfur dioxide (Li-S02) battery used with the equipment contains pressurized sulfur dioxide (S02) gas. The
gas is toxic, and the battery MUST NOT be abused in any way which may cause the battery to rupture.
WARNING
DO NOT heat, short circuit, crush, puncture, mutilate, or disassemble batteries.
WARNING
DO NOT USE any battery which shows signs of damage, such as bulging, swelling, disfigurement, brown liquid in
the plastic wrap, a swollen plastic wrap, etc.
WARNING
DO NOT test Li-S02 batteries for capacity.
WARNING
DO NOT recharge Li-S02 batteries.
Change 8 G
TM-11-5820-590-12-1
WARNING
DO NOT use water to extinguish Li-SO2 battery fires if a shock hazard exists due to high voltage electrical
equipment in the immediate vicinity (i.e., greater than 30 volts, alternating current (ac) or direct current
(dc)).
WARNING
If the battery compartment becomes hot to the touch, if you hear a hissing sound (i.e., battery venting), or smell
irritating sulfur dioxide gas, IMMEDIATELY Turn Off the equipment. Remove the equipment to a well ventilated
area or leave the area.
WARNING
DO NOT use a Halon type fire extinguisher on a lithium battery fire.
WARNING
In the event of a fire, near a lithium battery(ies), rapid cooling of the battery(ies) is important. Use a carbon dioxide
(C02) extinguisher. Control of the equipment fire, and cooling, may prevent the battery from venting and potentially
exposing lithium metal. In the event that lithium metal becomes involved in fire, the use of a graphite based Class
D fire extinguisher is recommended, such as Lith-X or MET-L-X.
WARNING
DO NOT store lithium batteries with other hazardous materials and keep them away from open flame or heat.
Change 8 H
TM 11-5820-590-12-1
TECHNICAL MANUAL
No. 11-5820-590-12-1
MAINTENANCE MANUAL (INCLUDING REPAIR PARTS
RADIO SETS AN/PRC-74B (NSN 5820-00-935-0030) AND
POWER SUPPLIES PP-4514/PRC-74(NSN 5820-00-942-0821) AND
BATTERY BOXES CY-6121/PRC-74(NSN 5820-00-908-3127),AND
REPORTING ERRORS AND RECOMMENDINGIMPROVEMENTS
You can help improve this manual. If you find any mistakes or if you know of
a way to improve the procedures, please let us know. Mail your letter, DA
Form 2028 (Recommended Changes to Publications and Blank Forms), or
DA Form 2028-2 located in back of this manual direct to: Commander, US
Army Communications-Electronics Command and Fort Monmouth, ATTN:
AMSEL-ME-MP, Fort Monmouth, New Jersey 07703-5000.
In either case, a reply will be furnished direct to you.
HEADQUARTERS
DEPARTMENT OF THE ARMY
WASHINGTON, DC, 3 March 1967
OPERATOR'S AND ORGANIZATIONAL
AND SPECIAL TOOLS LISTS)
AN/PRC-74C (NSN 5820-00-177-1641); AND
PP-4514A/PRC-74(NSN 5820-00-177-4581); AND
CY-6314/PRC-74 (NSN 5820-00-935-0382)
AND CY-6314A/PRC-74 (NSN 5820-0-156-3934)
CHAPTER 1. INTRODUCTION
Section I. General
Scope ...................................................................................................... 1-1 1-1
Consolidated Index of Army Publications and Blank Forms ................... .. 1-2
Maintenance Forms, Records, and Reports ............................................ . 1-3
Reporting Equipment Improvement Recommendations (EIRs) ............... . 1-3.1
Administrative Storage ................. ........................................................... 1-3.2
Destruction of Army Electronics Materiel . ................................................ 3-3.3
II. Description and Data
Purpose and Use ..................................................................................... 1-4
Technical Characteristics ......................................................................... 1-5
Components of Radio Set AN/PRC-74B . . . ............................................. 1-6
Description of Major Components ............................................................ 1-7
Description of Power Supply PP-45 1 4/PRC-74 ...................................... 1-8
CHAPTER 2. INSTALLATION
Unpacking .................................... ........................................................... 2-1 2-1
Checking Unpacked Equipment ............................................................... 2-2 2-2
Radio Set Installation ............................................................................... 2-3 2-1
Siting ....................................................................................................... 2-4 2-2
Antenna Assembly.................................................................................... 2-5 2-2
CHAPTER 3. OPERATING INSTRUCTIONS
Controls and Indicators ............................................................................ 3-1 3-1
Receiver Tuning ...................................................................................... 3-2 3-2
Paragraph Page
Change 8 i
TM 11-5820-590-12-1
Transmitter tuning .................................................................................... 3-3 3-2
Coder-burst operation .............................................................................. 3-4 3-3
Netting procedure .................................................................................... 3-5 3-4
Battery charger operation ......................................................................... 3-6 3-4
CHAPTER 4. OPERATOR'S MAINTENANCE INSTRUCTIONS
Scope of operator's maintenance ............................................................. 4-1 4-1
Operator's preventive maintenance .......................................................... 4-2 4-1
Preventive maintenance checks and services periods ............................. 4-3 4-1
Operator's daily preventive maintenance checks and services chart ........ 4-4 4-1
Operator's weekly preventive maintenance checks and services chart...... 4-5 4-2
Cleaning................................................................................................... 4-6 4-2
Dry battery replacement ........................................................................... 4-7 4-2
CHAPTER 5. ORGANIZATIONAL MAINTENANCE INSTRUCTIONS
Section I. Organizational Maintenance
Scope of organizational maintenance ...................................................... 5-1 5-1
Tools, materials, and test equipment required .......................................... 5-2 5-1
Organizational preventive maintenance ................................................... 5-3 5-1
Organizational monthly preventive maintenance checks and services...... 5-4 5-1
Organizational monthly preventive maintenance checks and services chart 5-5 5-2
Quarterly maintenance ............................................................................. 5-6 5-2
Quarterly preventive maintenance checks and services chart .................. 5-7 5-2
Touchup painting instructions ................................................................... 5-8 5-3
II. Troubleshooting
General .................................................................................................... 5-9 5-3
Troubleshooting chart .............................................................................. 5-10 5-3
Supplementary rt unit troubleshooting information ................................... 5-11 5-4
Wet battery replacement ......................................................................... 5-12 5-4
Power Supply PP-4514/PRC-74 supplementary troubleshooting information 5-13 5-6
Paragraph Page
Change 7 ii
TM 11-5820-590-12-1
CHAPTER 6. SHIPMENT, LIMITED STORAGE, AND DEMOLITION TO PREVENT
ENEMY USE Illus
ParagraphPage Figure
Section I. Shipment and limited storage
Disassembly of equipment ..................................................................... 6-1 6-1
Repackaging for shipment or limited storage.......................................... 6-2 6-1
II. Demolition to prevent enemy use
Authority for demolition .......................................................................... 6-3 6-1
Methods of destruction............................................................................ 6-4 6-1
APPENDIX A. REFERENCES ...................................................................................... A-1
B. BASIC ISSUE ITEMS ............................................................................ B-1
C. MAINTENANCE ALLOCATION ............................................................. C-1
D. ORGANIZATIONAL MAINTENANCE REPAIR PARTS AND SPECIAL
TOOLS LIST
Section I. Introduction............................................................................................. D-1
II. Repair Parts List .................................................................................... D-4
Group 00 Radio Sets AN/PRC-74B and AN/PRC-74C ........................................... D-4 D-1
01 Receiver-Transmitter, Radio RT-794B/PRC-74 and RT-794C/PRC-74
0101 Receiver-Transmitter, Radio (No Parts Authorized)
010101 Module, Power Supply (No Parts Authorized)
010102 Module, IF/Audio (No Parts Authorized)
010103 Module, Frequency Generator (No Parts Authorized)
010104 Module, Synthesizer (No Parts Authorized)
010105 Module, Power Amplifier (No Parts Authorized)
010106 Module, Radio Frequency (No Parts Authorized)
010107 Panel and Chassis Assembly (No Parts Authorized)
Group 02 Accessories
0201 Accessories Assembly (No Parts Authorized)
020101 Bag, Accessories CW-863/PRC-74 (No Parts Authorized)
020102 Cable Assemblies CX-10239/PRC-74 D-7 D-2
020103 Headset, Electrical (See TM 11-5965-260-15P for parts)
020104 Microphone, M-80/U (See TM 11-5965-265-13P)
020105 Key, Telegraph KY-562/U (No Parts Authorized)
03 Antenna Kit MK-9IIA/PRC-74 and MK-9IIB/PRC-74
0301 Antenna Kit (No Parts Authorized)
04 Antenna AS-1887A/PRC-74
0401 Antenna (No Parts Authorized)
05 Base, Antenna Support AB-955/PRC-74
0501 Base, Antenna Support (No Parts Authorized)
06 Mounting MT-3613/PRC-74
0601 Mounting (No Parts Authorized)
07 Battery Box CY-6314/PRC-74 and CY-6314A/PRC-74
0701 Battery Box (No Parts Authorized)
070101 Battery Box Base Assembly (No Parts Authorized)
070102 Battery Rtnr Hdw and Cable Assembly D-8 D-3
070103 Battery Cover Assembly (No Parts Authorized)
08 Battery Box CY-6121/PRC-74
0801 Battery Box ................................................................................... D-8 D-4
09 Power Supply PP-4514/PRC-74 and PP-4514A/PRV-74
0901 Power Supply................................................................................. D-11 D-5
090101 Battery Charger Subassembly
09010101 Battery Charger Regulator (No Parts Authorized)
090102 Power Supply Subassembly (No Parts Authorized)
09010201 Power Supply Regulator (No Parts Authorized)
090103 Front Panel Subassembly (No Parts Authorized)
Section III. Special Tools List (Not Applicable)
IV. National Stock Number and Part Number Index...................................... D-13
Change 7 iii
C 2, TM 5820-590-12-1
Figure 1-1. Receiver-Transmitter, Radio RT-794B/PRC -74 with wet and dry battery packs.
v
TM-11-5820-590-12-1
Figure 1-1. Receiver-Transmitter, Radio RT-794B/PRC-74 with wet and dry battery packs
vi
C 2, TM 11-5820-590-12-1
Figure 1-1.1. Receiver-Transmitter Radio, RT-794C/PRC-74 with dry battery pack.
vi.1
CHAPTER 1
INTRODUCTION
Section I. GENERAL
TM 11-5820-590-12-1
1-1. Scope
This manual describes Radio Set AN/PRC-74B,
Radio Set AN/PRC-74C, Power Supply
PP4514/PRC-74, Power Supply PP-4514-A/PRC,
Battery Box CY-6121/PRC-74, Battery Box
CY6314/PRC-74, and Battery Box CY-6314A/PRC74 and covers their installation, operation, and
maintenance. Unless otherwise indicated,
references in this manual to Radio Set AN/PRC-74B
also apply to Radio Set AN/PRC-74C, references to
Power Supply PP-4514/PRC-74, and references to
Battery Box CY-6314/PRC-74 also apply to Battery
Box CY-6314A/PRC-74. Operator and
organizational maintenance instructions are limited
to those services listed in chapters 4 and 5 and in
appendix C.
1-2. Consolidated Index of Army
Publications and Blank Forms
Refer to the latest issue of DA Pam 25-30 to
determine whether there are new editions, changes
or additional publications pertaining to the
equipment.
1-3. Maintenance Forms, Records, and
Reports
a. Reports of Maintenance and Unsatisfactory
Equipment. Department of the Army forms and
procedures used for equipment maintenance will be
those prescribed by DA Pam 738-750, as contained
in Maintenance Management Update.
b. Report of Packaging and Handling
Deficiencies. Fill out and forward SF 364 (Report of
Discrepancy (ROD)) as prescribed in AR 735-
112/DLAR 4140.55/NAVMATINST 4355.73B/AFR
400-54/MCO 4430.3H.
c. Discrepancy in Shipment Report (DISREP)
(SF 361). Fill out and forward Discrepancy in
Shipment Report (DISREP) (SF 361) as prescribed
in AR 55-38/NAVSUPINST 4610.33C/AFR
7518/MCO P4610. 19D/DLAR 4500.15.
1-3.1 Reporting Equipment Improvement
Recommendations (ElRs)
If your equipment needs improvement, let us know.
Send us an EIR. You, the user, are the only one who
can tell us what you don't like about the design. Put
it on an SF 368 (Quality Deficiency Report). Mail it
to: Commander, US Army Communications
Electronics Command and Fort Monmouth, ATTN:
AMSEL-PA-MA-D, Fort Monmouth, New Jersey
07703-5000. We'll send you a reply.
1-3.2 Administrative Storage
Administrative storage of equipment issued to and
used by Army activities will have preventive
maintenance performed in accordance with the
PMCS charts before storing. When removing the
equipment from administrative storage, the PMCS
should be performed to assure operational readiness.
Disassembly and repacking of equipment for
shipment or limited storage are covered in
paragraphs 6-1 and 6-2.
1-3.3 Destruction of Army Electronic
Materiel
Destruction of Army electronics materiel to prevent
enemy use shall be in accordance with TM 750-2442.
Section II. DESCRIPTION AND DATA
1-4. Purpose and Use
a. Radio Set AN/PRC-74B (referred to
throughout this manual as the radio set) provides
dependable two-way communications within the
frequency range from 2 to 17.999 megacycles (mc).
Receiver-Transmitter, Radio RT-794B/PRC-74 (fig.
1-1), part of the radio set, is a single sideband (ssb)
transceiver which provides either voice or telegraph
Change 8 1-1
continuous-wave (cw) mode of communications.
Unless otherwise indicated, references in this manual
to Receiver Transmitter, Radio RT-794B/PRC-74
also apply to Receiver-Transmitter, Radio RT794CIPRC-74 (fig. 1-1.1). The radio set operates at
the low end of the high-frequency (HF) spectrum;
therefore, signals are propagated by both
groundwave and portable stations. This is called net
TM 11-5820-590-12-1
skywave. Groundwave propagation is normally
used for communications at distances up to 25
miles For greater distances, skywave propagation
is used and signals reach distant points by
refraction from the ionosphere. The operating
range of the radio set may be extended to several
hundred miles by proper selection of frequency,
antenna and time of day.
b. The radio set is primarily designed for use
as, man pack set in areas where direct line-of-sight
communication is not possible.
1-5. Technical Characteristics
a. Receiver-Transmitter Radio RT-794B/PRC74
Frequency range...................... 2.000 to 17.999 mc in 1.0 kc
steps.
Frequency standard
stability.................................... ± 1.5 parts/million from -30°C to
+55°C (AN(PRC-74B).± 1.5
parts/million from -40°C to
+65°C (AN/PRC-74C).
Intermediate frequency............ 1,750 kc.
Transmitter performance:
Modulation modes................... Upper-sideband suppressed
carrier, voice or cw.
Carrier suppression.................. 40 db below level of a 1,000-
cycle modulation usb signal
of rated output.
Power output............................ 15 watts peak envelope power
nominal.
Monitor sidetone...................... Voice or tone as determined by
modulation mode.
Tuning indicator...................... Meter (operated by vswr bridge).
Receiver performance:
Sensitivity................................ 0.7 microvolt for 10 db, signal
plus noise to noise.
Selectivity................................ .3-db points at +300 and + 2,700
cps, 45-db points at -350
and + 6,500 cps (referenced
to carrier frequency).
Audio output............................ 1 mw minimum into a 500-ohm
headset.
Audio distortion....................... 10 percent maximum at
frequencies between 300
cps and 2,700 cps with an
audio output level of 4
milliwatts.
Power source............................ Determined by fixed or portable
requirements: An external
power supply may be used
as a power source during
fixed operation. For portable
use, wet or dry battery pack
may be used.
Input power.............................. + 10.5 to + 17.0 volts.
NOTE
The common name for Battery Box CY6121/PRC-74 is the wet battery pack and
the CY-6314/PRC-74 is the dry battery
pack.
Wet cell:
Type....................................... Rechargeable nickel-cadmium
Capacity................................. 14-ampere hours
Life......................................... 24 hours with a 1-minute
transmit/9-minute receive
continuous duty cycle
Terminal voltage..................... 1.2 volts per cell (wet battery pack
terminal voltage is 12 volts).
Terminal voltage...................... + 12 volts
Dry cell
Type......................................... BA-4386/U
Quantity................................... 2 batteries per pack
Terminal voltage...................... 15 volts dc per cell (dry battery
pack terminal voltage is + 15
volts).
Capacity................................... 14-ampere hours.
Life........................................... 24 hours, 9 minutes receive, 1
minute transmit duty cycle.
Type......................................... BA-5598/U
Terminal voltage...................... 12 volts dc.
c. Power Supply PP-4514/PRC-74.
NOTE
Unless otherwise indicated, references in
this manual to Power Supply PP4514/PRC-74 also apply to Power Supply
PP-4514A/PRC-74.
This power supply is used with but not part of the
AN/PRC-74B. It is used with the AN/PRC-74B to
recharge the wet battery and to provide a 14-volt dc
source during vehicular or semi-permanent
operation (pare 2-3b and c). The power supply is
issued with four power cables and one battery
charger cable (fig.1-8).
Input......................................... + 28 volts, + 10 percent to -25
percent, 110 volts or 220 volts
single phase, + 15 percent to -25
percent at line frequency from 47
to 400 cps.
b. Battery Box CY-6121/PRC-74 and Battery
Box CY-6314/PRC-74.
CHANGE 8
1-2
Power supply module:
Output voltage......................
.........
Ripple voltage at output...............
......
Battery charger module, charging
rate to wet cell battery...........
........
+14 volts ±3 at load currents
between 0 and 6.5 amperes
1.0 volt peak-to-peak maximum.
Variable from 1 to 5 amperes.
1-6. List of Components
Note. Power Supply PP-4514( )/PRC-74, Battery
Box CY-6121/PRC-74, and Battery Box CY-6314
()/PRC-74 are used with but not part of the radio
set.
a. Radio Set AN/PRC-74B Only (fig. 1-3
through 1-7). The following list of components is
for Radio Set AN/PRC-74B (FSN 5820-335-0030).
Quantity
1......... Receiver Transmitter, Radio
1......... Bag, Accessory,
1......... Mounting, MT-3613/PRC-74 5820-942-0818
1......... Base, Antenna Support AB-
1......... Antenna, AS-1887A/PRC-74 5820-935-0032
1......... Kit, Wire Antenna MK-
1......... Key, Telegraph KY-562/U 5805-926-0221
1......... Headset, Electrical H-140( )/U 5965-892-1010
1......... Microphone, Dynamic M-80/U 5965-875-1313
1......... Cable, Assembly, Special
Item
RT-794B/PRC-74
CW-863/PRC-74
955/PRC-74
911A/PRC-74
Purpose CX-10239/PRC-74
(used with Keyer KY468/GRA-71) Running
spares (para 1-6.1)
FSN
5820-935-0031
8105-921-6711
5820-942-0500
5820-832-8210
5995-930-7016
TM 11-5820-590-12-1
1......... 110 Volt AC Power Cable W1
1......... 21-31 Volt DC Power Cable W2
1......... 220 Volt AC Power Cable W3
1......... 24 Volt DC Power Cable W4
1......... Battery Charger Cable W5 CX-
d. Battery Box CY-61211PRC-74 (fig. 1-2).
Battery Box CY-6121/PRC-74 (wet battery pack)
(FSN 5820-908-3127) is a self contained unit. The
following items (1) through (3) below are used with
but not part of the wet battery pack and must be
requisitioned separately.
(1) Ten each; Battery, Storage BB-418/U
(FSN 6140-855-7634).
(2) Ten each; intercell connectors (FSN
5940134-0724).
(3) One each; Power Supply PP-4514/PRC74 (FSN 5820-942-0821) or Power Supply
PP4514A/PRC-74 (FSN 5820-177-4581) for
recharging purposes.
e. Battery Box CY-6314( )/PRC-74 (fig. 4-1).
Battery Box CY-6314/PRC-74 (FSN 5820-935-
0382) and Battery Box CY-6314A/PRC-74 (FSN
6135-1563934) (both are called dry battery packs)
are self contained units.
74
5995-945-1936
CX-10296/U
5995-930-9083
CX-10297/U
5995-945-1900
CX-10298/U
5995-945-1882
CX- 10299/U
5995-945-1881
10300/U
Running Spares(para 1-6.1)
b. Radio Set AN/PRC-74C Only. Except for
Receiver Transmitter, Radio RT-794B/PRC-74 (rt
unit) the components and running spares for Radio
Set AN/PRC-74C (FSN 5820-177-1641) are the
same as the AN/PRC-71B (a above). The rt unit
for the AN/PRC-74C is Receiver Transmitter, Radio
RT-794C/PRC-74 (FSN 5820-177-1640).
c. Power Supply PP-4514( )/PRICE-74 (fig.
1-8). Power Supply PP-4514/PRC-74 (FSN 5820-
9420821) and Power Supply PP-4514-A/PRC-74
(FSN 5820-177-4581) contain the following items:
Quantity Item FSN
1......... Power Supply PP-4514/PR-C- 5820-942-0821
Change 8 1-3
1-6.1. Running Spares
a. The following is a list of running spare fuses
for the radio set:
In Use Quantity Item
1
1
B The following is a list of the running spare
fuses and lamps for Power Supply PP-4514/PRC74:
5
5
5 Fuses 1AG, 7.5 amp.
5 Fuses 1AG, 2 amp.
C 2, TM 11-5820-590-12-1
In use Quantity Item
1
1
2
1
2
1-7. Description of Major Components
transistorized receiver-transmitter that can be used
for either point-to-point or netting operation. The
radio set operates on a single frequency for both
transmit and receive functions. The transmitter is
enabled by a push to-talk microphone button, a
telegraph key, or automatic Keyer KY-468/GRA-71
(part of Coder-Burst Transmission Group
AN/GRA71) . Coder-burst Transmission Group AN/
GRA-71 is not supplied as part of the AN/PRC-74B.
The receiver is operative only when the transmitter
is not being used; therefore, communication is only
on a one-way reversible basis.
alternating current (ac) or direct current (dc)
powerlines, or from a 24-volt vehicle battery when
Power Supply PP-4514/PRC-74 is available.
During normal operation, the radio set is mancarried and operated from either Battery Box CY6314/PRC-74 (dry battery pack) or Battery Box CY6121/PRC-74 (wet battery pack) (fig. 1-2). Latches
on two sides of the receiver-transmitter (rt) permit
attachment to either the dry or wet battery pack, or
to Power Supply PP-4514/PRC-74 (external power
supply and battery charger). Retractable legs are
provided on the base of the wet battery pack to
support Receiver-Transmitter Radio RT-794B/PRC74 (rt unit) when it is used in an upright position.
either Whip Antenna AS-1887A/PRC— 74 ( fig. 1-
3) or various configurations of a wire antenna. The
Whip antenna consists of Mounting MT-3613/PRC74 (mounting bracket) which attaches to the radio
set (fig. 1-3), a Base, Antenna Support AB955/PRC-74 which attaches to the mounting
bracket, and the whip antenna which attaches to
the antenna support. Antenna Kit MK-911A/PRC74 (shown in the top half of fig. 1-4) consists of two
reels of antenna wire with the required antenna
3
5
5
6
3
2
Fuses F2A, 32 volts, 15 amp.
Fuses F2A, 250 volts, 2 amp.
Fuses F2A, 250 volts, 4 amp.
Fuses F3A, 250 volts, 6 amp.
Fuses F3A, 250 volts, 8 amp.
Lamps, MS-25237-327.
a. The radio set is a low-powered, fully
b. The radio set may be operated from
c.The radio set can be operated with the use of
which plugs and weights, two reels of Dacron cord,
and a dipole fixture. The components of the wire
antenna kit can be arranged in any of the
configurations described in paragraph 2-5.
d. Accessory equipment (fig. 1-5) includes
Headset H-140/U, Key, Telegraph KY-562/U, and
Microphone M-80/U. Bag, Accessories CW863/PRC-74 (fig. 1-6) is provided to store the
antennas and accessory equipment when they are
not in use. Cable Assembly, Special Purpose,
Electrical CX-10239/PRC-77 (fig. 1-7) permits the
use of the radio set with automatic Keyer KY468/GRA-71 (part of Coder-Burst Transmission
Group AN/GRA-71).
e. Battery Box CY-6314A/PRC-74 (fig. 12)
consists of two 15-volt battery blocks connected in
parallel to provide an open circuit terminal voltage
of + 15 volts. Battery capacity is 14-ampere hours
with life expectancy of 24 hours (9-minutes receive,
1-minute transmit duty cycle). The radio set will
operate on one battery block for a reduced time
period A battery terminal voltage of less than 11
volts, measured during transmission, indicates low
batteries which will result in a reduced radio
frequency (RF) power output from the radio set.
f. The wet cell battery (fig. 1-2) consists of 10
nickel-cadmium cells, connected in series, to
provide a nominal voltage of 12.0 volts. The open
circuit voltage of a discharged battery is 12.5 volts
or less, and that of a full' charged battery will be 13
volts or more. Unless otherwise indicated by a
warning tag or the battery, the wet cell battery is
always shipped in a discharged state.
1-8. Description of Power Supply PP—
451 4/PRC-74
(fig. 1-8)
This power supply is used with the AN/PRC-74B
when the radio set is installed in a vehicle or is
used in a semi-permanent location. This permits
the radio set to be operated from 110 or 220 volts
ac or 21 to 31 volts dc. Five power cables are
provided with the power supply
1-4
C 2, TM 11-5820-590-12-1
and are used to connect power from the available
voltage source to the power supply. The power
supply consists of a battery charger subassembly
and power supply subassembly The battery
charger subassembly contains a control for
adjusting the charging current from 0 to 5 amperes.
The power supply subassembly provides controls
and indicators to establish and monitor the charging
rate of the battery charger, the actual charge stored
in the wet cell battery, or the voltage supplied to the
radio set from the external power source.
1-4.1
C 2, TM 11-5820-590-12-1
Figure 1-2 Wet and dry battery carrier assemblies, covers removed.
1-4.2
TM 11-5820-590-12-1
Figure 1-3. Receiver -Transmitter Radio RT-794B/PRC-74 with whip antenna.
1-5
TM 11-5820-590-12-1
Figure 1-4. Whip antenna, antenna kit, and mounting hardware.
1-6
TM 11-5820-590-12-1
Figure 1-5. Headset, telegraph key, and microphone.
Figure 1-6, Bag, Accessories CW-863/PRC-74.
TM5820-590-12-1-18
TM5820-590-12-1-5
1-7
TM 11-5820-590-12-1
Figure 1-7. Cable Assembly, Special Purpose, Electrical CX-10239/PRC-74 (adapter cable for
automatic Keyer KY-468/GRA-71)
1-8
1-9. Differences in Models
Radio Set AN/PRC-74C differs from Radio Set
AN/PRC-74B in the following details:
a. The front panel assembly is marked in
Hertz ( Hz ) instead of cycles ( C ) and has molded
handles (fig. 3-1, 3-1.1).
b. The receiver-transmitter case has
ruggedized latches (fig. 1-1.1).
c. The frequency synthesizer relocates
calibrate crystal Y47 secures switch assemblies A1
and A4 with brackets and changes value of several
components .C 2, TM 11-5820-590-12-1.
d. The RF module has different chassis
plates.
C 2, TM 11-5820-590-12-1
e. The IF audio module has added capacitor.
f. The power supply module relocates several
components.
g. The frequency generator has added spring
clips.
h. All modules have components subject to
shifting, secured with sealant.
i. Battery Box CY-6314/PRC-74 differs from
Battery Box CY-6314A/PRC-74 in the way in which
batteries are mounted (para 4-7).
1-9
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