BC-375C_serv_user_1939.pdf
I INSTRUCTION BOOK FOR RADIO TRANSMITTER BC-375-C ORDER NO. 51-NY-40 AND ASSOCIATED EQUIPMENT MANUFACTURED BY GENERAL ELECTRIC COMPANY U.S.A. RESTRICTED PUBLISHED BY AUTHORITY OF THE CHIEF SIGNAL OFFICER DATE 8339 INSTRUCTION BOOK FOR RADIO TRANSMITTER BC-375-C AND ASSOCIATED EQUIPMENT MANUFACTURED BY GENERAL ELECTRIC COMPANY U.S. A. RESTRICTED Notice:-This document contains information affecting the national defense of the United States within the meaning of the Espionage Act (U.S.C. 50:31, 32). The trans- mission of this document or the revelation of its contents in any manner to any un- authorized person is prohibited. The information contained in documents marked RESTRICTED will not be communicated to the public or to the press, but it may be communicated to any person known to be in the service of the United States and to persons of undoubted loyalty and discretion who are co-operating in governmental work. (AR-380-5). ORDER NO. 51-NY-40 2-41 (1620) PUBLISHED BY AUTHORITY OF THE CHIEF SIGNAL OFFICER (GEI-12358A) DATE 8-339 SAFETY TO HUMAN LIFE OPERATION OF THIS EQUIPMENT INVOLVES THE USE OF HIGH VOLTAGES WHICH ARE DAN- GEROUS TO LIFE. OPERATING PERSONNEL MUST AT ALL TIMES OBSERVE ALL SAFETY REGULA- TIONS. DO NOT CHANGE TUBES OR MAKE ADJUST- MENTS INSIDE EQUIPMENT WITH HIGH-VOLTAGE SUPPLY ON. DO NOT COMPLETE OR MAINTAIN ANY CONNECTION BETWEEN TRANSMITTER AND DYNAMOTOR UNIT UNLESS ALL UNUSED SOCKETS ON THE TRANSMITTER ARE COVERED BY SOCKET CAPS WITH CATCHES PROPERLY SNAPPED IN PLACE. KEEP AWAY FROM LIVE CIRCUITS 1. Under no circumstances should any person be per- mitted to operate the dynamotor with relay-fuse box cover or end bells removed; or to replace fuses with power on; or to remove, place, or handle removed plugs with the dynamotor running. 2. Under no circumstances adjust circuits or service the equipment when the carrier is keyed off only. The transmitter uses a grid-bias keying circuit, which does not remove high voltage when the key is open. DO NOT OPERATE THE EQUIPMENT WITH SHIELDS REMOVED lll LIST OF ILLUSTRATIONS Page Fig. 1. Radio Transmitter BC-375-C and Associated Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vm Fig. 2. Antenna Tuning Unit BC-306-A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Fig. 3. Case CS-48 and Rear View of a Transmitter Tuning Unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Fig. 4. Dynamotor Unit PE-73-B. . . . . . . . 3 Fig. 5. Radio Transmitter BC-375-C, with Transmitter Tuning Unit TU-22-A in Place. . . . . . . . . . . . . . . 4 Fig. G. Typical Front View of a Transmitter Tuning Unit without a Band Change Switch. . . . . . . . 5 Fig. 7. Mounting FT-115-B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Fig. 8. Radio Transmitter BC-375-C, with Tube Compartment Shield Removed and Transmitter Tuning Unit TU-22-A Being Inserted. . . . . . . . . . . . . . 9 Fig. 9. Radio Transmitter BC-375-C, Filament Resistor and Terminal Board. . . . . . . . . . . . . . . . . . . . . . 10 Fig. 10. Antenna Reactance Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Fig. 11. Radio Transmitter BC-375-C, Functional Diagram of Radio-Frequency and High-Voltage Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Fig. 12. Radio Transmitter BC-375-C, Functional Diagram of Antenna Tuning Circuits. . . . . . . . . . . . . . 19 Fig. 13. Radio Transmitter BC-375-C, Functional Diagram of Audio-Frequency Circuits-Tone Opera- tion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Fig. 14. Radio Transmitter BC-375-C, Functional Diagram of Audio-Frequency Circuits- CW Operation (Side Tone). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Fig. 15. Radio Transmitter BC-375-C, Functional Diagram of Audio-Frequency Circuits- Voice Opera- tion . . . . . . 21 Fig. Hi. Radio Transmitter BC-375-C, Functional Diagram of Low-Voltage and Control Circuits. . 22 Fig. 17. Tube VT -4-C, Characteristic Curves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Fig. 18. Tube VT-25, Characteristic Curves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Fig. 19. Antenna Tuning Unit BC-306-A, Schematic Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Fig. 20. Dynamotor Unit PE-73-B, Schematic Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Fig. 21. Antenna Tuning Unit BC-306-A, Interior View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Fig. 22. Dynamotor Unit PE-73-B; Mounting FT-107 and Low-Voltage End Bell Removed. . . . 52 Fig. 23. Dynamotor Unit PE-73-B; Mounting FT-107 and High-Voltage End Bell Removed. 53 Fig. 24. Dynamotor Unit PE-73-B, Top View; with Mounting FT-107 and Relay-Fuse Box Cover Removed. . . . . . . . . . 54 Fig. 2.). Radio Transmitter BC-375-C, Tube Compartment Shield and Top. Cover Off and Transmitter Tuning Unit in Place. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Fig. 26. Radio Transmitter BC-375-C, Rear View; Mounting FT-151-A and Shields Removed . . . . . 56 Fig. 27. Radio Transmitter BC-375-C, Rear View; Mounting FT-151-A and Shields Removed. . . 57 Fig. 28. Radio Transmitter BC-375-C, Bottom View; Mounting FT-151-A and Shields Removed. 58 Fig. 29. Transmitter Tuning Unit TU -5-A, Top View, Cover Removed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Fig. 30. Transmitter Tuning Unit TU-5-A, Bottom View, Cover Removed . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Fig. 31. Transmitter Tuning Unit TU-6-A, Top View, Cover Removed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Fig. 32. Transmitter Tuning Unit TU-6-A, Bottom View, Cover Removed . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Fig. 33. Transmitter Tuning Unit TU 7-A, Top View. Cover Removed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Fig. 34. Transmitter Tuning Unit TU-7-A, Bottom View, Cover Removed. . . . . . . . . . . . . . . . . . . . . . . . . . 61 Fig. 35. Transmitter Tuning Unit TU-8-A. Top View, Cover Removed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Fig. 36. Transmitter Tuning Unit TU-8-A, Bottom View, Cover Removed . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Fig. 37. Transmitter Tuning Unit TU-9-A, Top View, Cover Removed. . . . . . . . 63 Fig. 38. Transmitter Tuning Unit TU-9-A, Bottom View, Cover Removed . . . . . 63 Fig. 39. Transmitter Tuning Unit TU-10-A, Top View, Cover Removed . . 64 Fig. 40. Transmitter Tuning Unit TU-10-A, Bottom View, Cover Removed . . . . . . . . . . . . . . . . . . . . . . . . . 64 Fig. 41. Transmitter Tuning Unit TU-22-A, Top View, Cover Removed. . . . . 65 Fig. 42. Transmitter Tuning Unit TU-22-A, Bottom View, Cover Removed . . . . . . . . . . . . . . . . . . . . . . . . . 65 Fig. 43. Antenna Tuning Unit BC-306-A, Connection Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Fig. 44. Antenna Tuning Unit BC-306-A, Dimensions and Weight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 Fig. 45. Case CS-48, Dimensions and Weight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Fig. 46. Dynamotor Unit PE-73-B, Connection Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Vl LIST OF ILLUSTRATIONS (Contd) Page Fig. 47. Dynamotor Unit PE-73-B, Dimensions and Weight. . 71 Fig. 48. Mounting FT-115-B, Dimensions and Weight. . . 72 Fig. 49. Radio Transmitter BC-375-C, Schematic Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Fig. 50. Radio Transmitter BC-375-C, Connection Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Fig. 51. Radio Transmitter BC-375-C, Dimensions and Weight. 75 Fig. 52. Transmitter Tuning Units, Schematic Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Fig. 53. Transmitter Tuning Unit TU-5-A, Connection Diagram . _. 77 Fig. 54. Transmitter Tuning Unit TU-6-A, Connection Diagram . . . . _ . _ . . . . . . . . . . 78 Fig. 55. Transmitter Tuning Unit TU-7-A, Connection Diagram . _. _ . _ . _. . . . . . . . . . . . . . . . . . . . . . . 79 Fig. 56. Transmitter Tuning Unit TU-8-A, Connection Diagram . _. _ . _ . . . . . . . . . . . . . . . . . . 80 Fig. 57. Transmitter Tuning Unit TU-9-A, Connection Diagram . _ . _. _. . . . . . . . . . . . . . . . 81 Fig. 58. Transmitter Tuning Unit TU-10-A, Connection Diagram . _. _. . . . . . . . . . . . . . . . . . . . . . . 82 Fig. 59. Transmitter Tuning Unit TU-22-A, Connection Diagram_ . . _. . . . . . . . . . . . . . . . . . . . . 83 Fig. 60. Radio Set SCR-287-A, Cording Diagram . _. . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Vll Dynamotor Unit PE-73-B Mounting FT-115-B Maintenance Parts Radio Transmittttr BC-375-C with its asso- ciated equipment is designed for aircraft and other applications requiring a medium power equipment with the characteristics of strength, light weight, flexibility, and portability. The equipment is designed to provide communication by voice, tone, or con- tinuous-wave telegraphy over the frequency range of 150 to 12,500 kilocycles. However, only the fre- quencies covere.d by the Transmitter Tuning Units listed in paragraph 15 are available for use with this equipment. Suitable tuning equipment is provided in the radio transmitter to permit operation into a wide range of antennas over most of the frequency range. Antenna Tuning Unit BC-306-A may be used to extend the range of antenna tuning for frequencies between 150 and 800 kilocycles. ? Dynamotor Unit PE-73-B furnishes the power required by the radio transmitter and operates from Ant<zn na -1-1 Ground a 24/28 volt storage battery or other direct-current source used in aircraft. The input power when operating on continuous-wave telegraph will be approximately 600 watts. The fully modulated voice transmission will require 840 watts. input power. 3. Because of the flexibility with which it can be adapted to fit different requirements and conditions of operation, Radio Transmitter BC-375-C may be used as an item of a number of different radio sets. The other items, such as tuning units, cords, etc., wil1 be listed in the Parts List of each set. ANTENNA TUNING UNIT BC-306-A (INCLUDES MOUNTING FT-142) 4. This unit consists of a painted duralumin case which houses a variometer 1502, control F; and a switch 1501, control E. Sufficient inductive reactance is provided in this unit, in addition to the reactance provided in the transmitter and transmitter tuning Mounting FT-142 FrG. 2. ANTENNA TUNING UNIT BC-306-A v Pars. 4-7 units, to resonate antennas whose effective capacitance varies as indicated below: Frequency Range 150-350 kc 350-800 kc Effective Capacitance Range 1000-1500 mmfds. 350-800 mmfds. 5. The controls permit a continuous variation of the inductive reactance. Suitably insulated binding posts are located on the top shield. Four snap-slide catches are used to attach the unit to Mounting FT-142. 6. The terminals at the top of the antenna tuning unit are for interconnection between the loading terminals of the radio transmitter when operatmg on frequencies above 400 kilocycles. For operation on frequencies below 400 kilocycles, the antenna tuning unit is connected in the antenna circuit and the two loading terminals are connected together as de- scribed in section II, EMPLOYMENT. CASE CS-48 7. This case consists of an individual metal co tainer into which any one of the transmitter tuning units may be inserted and mounted or carried. The tuning unit is secured in the case by the same four snap-slide catches that are used to secure the unit in the radio transmitter. FIG. 3. CASE CS-48 AND REAR VIEW OF A TRANSMITTER TUNING UNIT 2 Pars. 8-ll DYNAMOTOR UNIT PE-73-B (INCLUDES MOUNTING FT-107) 8. Dynamotor Unit PE-73-B consists of a dyna- motor upon which is mounted a box containing the relay, fuses, sockets, capacitor, etc. The dynamotor proper is a two-pole, totally-enclosed, ball-bearing, d-e to d-e rotating machine. It is rated at 28 volts, 20 amperes input; 1000 volts, 0.35 amperes output, at 5000 rpm, with 55 deg. Centigrade rise for 72 hour intermittent duty. It has been designed to give efficient, reliable service over long periods of time with a minimum of attention. Skeleton type bearing brackets on each end afford maximum accessibility of the commutators and brushes. The portion of the armature winding between each commutator and armature core is securely bound with cord and thoroughly impregnated, thus affording a mechanical protection for the armature winding against injury from moisture, dirt, and abrasion. The external leads of the dynamotor go directly into the relay-fuse box through two bushings in the top of the magnet frame. 9. A totally-enclosed, solenoid-type starting relay, particularly designed to withstand vibration, sudden shock and acceleration as encountered in aircraft installation is used. The double-break contacts are sufficiently large to carry the heavy starting current of the dynamotor. 10. The input binding posts and fuse clips are mounted on and securely pinned to a molded terminal board. In addition, all fuse clips and terminals are soldered to their mounting screws so as to insure a tight, low resistance, electrical contact. 11. Four snap-slide catches are employed to fasten the cover to the relay-fuse box. A spare H.V. fuse, spare fuse links, and a socket wrench are carried in clips inside of this cover. In one end of
