RT-70_serv_user_1950.pdf

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1、INSTRUCTION BOOK FOR RECEIVER-TRANSMITTER /RT-70/GRC A,/i:;,;./ . Tt1 . 1L-:-.21.o . _ D:t:e . - ii.-:1. . . T T FEDERAL TELEPHONE pOl -:-p,o-1 RELAY SUPPLY I I CKT I FILa MIC iiREGULATING FILAMENT I CIRCUIT o-RELAY a - I SUPPLY MIC SUPPLY I I I I I I I - I I PLATE a IREGULATINGr VIBRATOR SCREEN SUP

2、 I CIRCUIT -r- POWER 1- SUPPLY 1 REG FILS SET I REG I OUTPUT I I I .v j COMMON INTERMEDIATE I I - CHANNEL 8 OUTPUT I SET 2. AMPLIFIER AMPL STAGES I -RECEIVER REC OUTPU L _ L _ _ - I BATTERY TO OTHER CONTROL STATIONS .L TM290-3 Figure 4. Application of Receiver-Transmitter RT-70/GRC to Radio Set AN/V

3、RC-7, simplified block diagram. 6.3 volts at 360 rna for fila- ments. 6.3 volts at 160 rna for relay (transmit only). The above voltages obtainable either from dry batteries in Case CY-590/GRC or from vibrator-type Power Supply PP-448/GR, Power Supply PP-281/GRC, or Power Supply PP-282/GRC and 6-, 1

4、2-, or 24-volt stor- age battery, respectively, through AF Amplifier AM- 65/GRC. Antenna requirements . Common whip-type antenna 50-ohm impedance. b. TRANSMITIER CIRCUIT. Power output . 50 mw ( milliwatts). Maximum modulation frequency deviation . 20 kc at 1,000 cps (cycles per second) with .25-volt

5、 input. Carrier frequency generation . Continuously variable 32- to 43.4-mc self-excited oscilla- tor and 2d harmonic of crystal controlled mixer os- cillator. Transmitter mixer oscillator frequency . 7.5 me. Type of operational control . Push-to-talk transmitter nor- mally in stand-by condition. Po

6、wer input requirements: Plate and screen . 90 volts Filament . 6.3 volts Relay . 6.3 volts Transmitting 80 rna. 360 rna. 160 rna. Transmitter audio input . 150 ohms at 1,000 cps. Transmitter audio input level . 25 volts rms (root mean square) at 1,000 cps. c. RECEIVER CIRCUIT. Type of receiver circu

7、it . Double conversion superhet- erodyne. First intermediate frequency 15 me. 5 First mixer oscillator tuning range . 32 to 43.4 me. Second intermediate frequency . 1.4 me. Second mixer oscillator frequency . . . . . 6.8 me. Type of operational control . Receiver normally in stand-by condition and s

8、ilenced by squelch action. Turned on by signals having a mini- mum level determined by setting of SQUELCH con- trol. Sensitivity . 25 db (decibel) signal-to- Bandwidth: noise ratio at 1.0 microvolt -15-kc deviation at 1,000 cps. 6 db down . 80 kc. 20 db down . 120 kc. 40 db drwn . Not over 180 kc Au

9、dio power output . 75 mw maximum for 15-kc deviation at 1,000 cps. Audio power output control . Continuously variable by means of panel -mounted VOLUME control. Audio output impedance . 600 ohms Noise suppression sensitivity (squelch) . Yz microvolt, approximately. Squelch control . Continuously var

10、iable, panel- mounted SQUELCH con- trol adjusts squelch sensi- tivity. OFF position of con- trol disables squelch circuit. Power input requirements: Receive Trammit Plate and screen . 90 volts 80 rna 80 rna. Filament . 6.3 volts 360 rna 390 rna. Relay . 6.3 volts 0 160 rna. d. CALIBRATION. Calibrate

11、 frequencies . At each me from 47 through 58 me. Built-in calibrate oscillator (crystal-controlled) . . . . . . . . 1 me. Built-in oscillator (crystal-controlled) . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 me. Accuracy of calibrate oscillator . 01 percent, approximately. 6. Description of

12、 Receiver-Transmitter RT-70/GRC a. Receiver-Transmitter RT-70/GRC is a combination double-conversion type superheterodyne receiver and f-m transmitter with common antenna circuit. It is designed for the reception and transmission of f-m voice signals within the continuously variable tuning range of

13、47 to 58.4 me. 6 b. A front view of Receiver-Transmitter RT-70/GRC is shown in figure 1. The unit is a compact, lightweight panel- and-chassis assembly with outer cover. All operating con- trols, cable connectOrs, and indicatOrs are mounted on the front panel and are immediately accessible. The pane

14、l is recessed to prevent damage to panel-mounted parts due to impacr. The panel is finished in a wrinkled olive drab lac- quer. Important panel markings are made luminous and a dial light is provided to permit the unit to be operated in the dark. An outer cover is attached to the front panel by mean

15、s of wing-type spring-loaded Dzus fasteners, making the unit watertight. A hole on the top of the outer cover gives access to the antenna trimmer capacitor. This hole is covered with a watertight cap. Snap catches are provided on the outer cover so that the unit can be mounted on AF Amplifier AM-65/

16、GRC when it is used in a vehicular installation. No carrying handles are provided for portable use since the unit is arranged to fit on Case CY-590/GR which is equipped with carrying facilities. The cover is finished in an olive green lacquer. It may be removed by turning the Dzus fasteners on the f

17、ront panel turn and sliding off the cover from the rear. The dimensions of the entire unit are 12 13 inches x 7 V! inches x 5 V! inches. The weight of the complete unit with outer cover is 1634 pounds. c. Figures 5 through 8 show Receiver-Transmitter RT- 70/GRC removed from the case. The panel-and-c

18、hassis assembly consists of three separable parts, namely: a front panel, an r-f chassis, and an i-f (intermediate-frequency) chassis. The r-f chassis mounts the h-f (high-frequency) components of both the transmitting and receiving circuits. The receiver i-f components and the audio components of b

19、oth the transmitter and receiver are mounted on the i-f chassis. Both chassis are attached to projections at the rear of the front panel by means of screws and are so arranged that all internal tuning adjustment controls, tubes, and other plug-in parts are accessible without further dis- assembly of

20、 the unit. No solder connections are made be- tween the r-f and i-f chassis or between these chassis and the front panel. Multiconnectors establish continuity be- tween the chassis and the panel controls and connectOrs. A rigid assembly is assured by a back plate, which is fastened tO the two chassi

21、s by means of heavy captive screws and by two bracing screws, located coward the middle of the r-f chassis, which effectively clamp the r-f chassis to the i-f chassis. By removing the retaining and bracing screws and the back plate, disconnecting the multiconnectors and the two pin connectors joinin

22、g the r-f and i-f circuits, and loosening the coupling between the dial-drive mechanism on the front panel and the shaft of the tuning capacitor on the r-f chassis, either one or both chassis may be removed for maintenance purposes. An important feature of the assembly is that a complete chassis can

23、 be substituted if either the r-f or i-f chassis of the set is defective. E-101 P-1 TERMINAL BOARD c-27 I-F CHASSIS R-F CHASSIS ALLEN WRENCHES V-1 T -I L-3 V-II T-3 T -10 L-10 TM290-5 Figure 5. Receit,er-Tra11smi1ter RT-70/GRC, case remo11ed1 top view of panel-and-chassis assembly. 7 8 V-1 CIRCUIT L

24、ABEL V-II PART OF C-IOA v - 10 T-9 V-8 MTG. SCREW P-2 RETAINING BOLTS SCREW BACK PLATE TUBE PULLER H-317 V-2 c-4 y -I C- 3 V- 3 OBSERVATION HOLE V- 4 V - 5 c -10 V - 6 MTG SCREW _._ftirii-H-31 3 Figure 6. Receiver-Trammitter RT-70/GRC, case removed, 1 iew of r-f chassis (right side o/ Pmel-anrl-chas

25、sis assembly) . RETA INING BOLTS S-2 0 I -iir:. R-202-1 J-202 -BACK PLATE CAPTIVE BRACING SCREWS S-202 Figure 7. Receiver-Transmitter RT-70/GRC, case removed; view of i-f chassis (left side of panel-and-chassis assembly). 9 V-2 V-3 V-4 E-1 V5 E-2 L-23 P201 J. I 10 R F CHASSIS I-F CHASS IS Figure 8.

26、Recei11er-Transmitter RT-70/ GRC, case remo11ed, bottom view of panel-and-chassis assembly. T-104 T-3 E103 VI04 EI05 T-105 E104 V-105 T-6 C35 T-106 L-16 T-107 E-106 VI06 Y-102 TM290- 8 ( 1) Front panel. The cast-aluminum front panel mounts all operating controls and connectors (fig. 1) and the dial-

27、 drive and detent mechanism (fig. 36). The dial-drive assembly, mounted on the rear of the front panel, couples mechanically to the shaft of the r-f tuning gang capacitor (C. 10) , mounted on the component side of the d chassis. A set of Allen wrenches, provided with the equipment, is mounted in a b

28、racket at the rear of the panel (fig. 36). (2) Rf chassis (figs. 6, 39, 40, and 41). The r-f chassis is located on the right side of the panel-and-chassis assem bly. It mounts the audio and r-f components of the trans- mitter and the h-f portion of the receiver, the variable 32- to 43.4-mc oscillato

29、r, V-2, and calibrate oscillator V-7, in- cluding ganged tuning capacitor (C. 10), crystals, and asso- ciated parts. The slotted plates, shuwn mounted at the rear of the gang capacitor (referenced as Parr of C10A on figure 6) serve for calibrating the section of gang capacitor ClOA which runes the v

30、ariable 32- to 43.4-mc common oscillator, V-2. A tube puller and a circuit label are provided on the r-f chassis. The tuning coils for the r-f circuits are grouped in two compartments, mounted on the wiring side of the r-f chassis. These compartments (fig. 40) are identi ANT ADJ MCS fied as T-3 and

31、T-4 through T-8, respectively. Partitions on the r-f coil compartment cover (fig. 41) separate the larger of the two compartments into a number of sections identi fied as T-4 through T-8. Tuning a justment controls for the coils in these compartments are accessible from the top (fig. 5) and bottom (

32、fig. 8) of the panel-and-chassis assembly. (3) J.f chassis. The i-f chassis (figs. 7, 37, and 38) mounts the components of the receiver i-f amplifier, squelch and audio circuits. The receiver-transmitter control relay and TANK-VEH-FIELD switch (S-101) are also mounted on the i-f chassis. 7. Controls

33、, Instruments, and Connectors (fig. 9) All operating controls and external connectors appear on the front panel of the receiver-transmitter. The antenna tuning adjustment capacitor C-41 (fig. 5) is accessible from the top of the ourer cover when the cap is removed. The location of panel controls and

34、 connectors is shown in figure 9. The following table lists the controls and con- nectors and indicates tr.e function of each. ANT n LOCK LOCK VOLUME I SQUELCH I pi1H0Mo.Q / OFF-! AUDIO POWER TM290-9 Figure 9. Receiver-Transmitter RT-70/GRC, panel controls and connectors. 11 12 Control or connector

35、TENTHS-MCS tuning knob MCS dial LOCK detent levers LAMP (E-201) SQUELCH control (R-202 and S-201) Function Calibrated m tenths of an me. One complete rotation tunes the receiver- transmitter over one me. Calibra- tion marker above knob constitutes a reference point when the knob is reset to zero adj

36、ustment. Zero adjust- ment is accomplished by holding the knob in fixed position and rotating plate under knob until zero on plate lines up with calibration marker on panel, when the set IS tuned to a signal on an integral megacycle. Calibrated 1n me from 47 through 58. One complete rotation of tuni

37、ng knob changes dial setting by one me. Frequency indication between me markings obtainable from setting of TENTHS-MCS tuning knob. Tuning frequency of set is sum of nearest lower dial number plus calibration marking on knob. Two levers, one on each side of the dial lamp. Each serves (independently

38、of the ocher) to actuate a detent mech- anism to detent or preset the dial- drive mechanism at any posicion within the tuning range. The detent mechanism is spring pre- loaded so that the dial drive may be forced to rotate past the detaining point. However, the next time around, the increased pressu

39、re required to drive the dial past the particular point serves as indication that desired frequency setting has been reached. A plastic marker (PRESET 1 and PRESET 2) associated with each de- tent lever permits recording the fre- quency to which the particular detent has been set. A pilot light, in

40、holder with screw-on cover immediately above tuning knob illuminates calibration markings of knob and dial. Two lucite windows in holder distribute light to dial and knob. Light turned on when switch ( S-202) is in any one of three test positions. Lamp extinguished when switch is 1n DIAL LIGHT OFF p

41、osition. (See function of ANT ADJ-DIAL LIGHT (ON-OFF)-CAL switch.) This switch and potentiometer assembly serves to adjust the degree of the receiver squelch or noise quieting. In the maximum counterclockwise direc- tion of rotation of the knob the switch is turned OFF and the squelch Control or con

42、nector VOLUME (R-204) ANT AD-DIAL LIGHT (ON- OFF) -CAL (S-202) Function (or receiver noise quieting circuit) is disabled, providing no receiver quiet- ing. In the clockwise direction of rotation, increasingly scrongr signals are required to disable the squelch and restore the receiver audio ampli- f

43、ier circuits to normal operation. For any setting of the potentiometer, a particular signal-plus-noise-co-noise ratio is determined below which the receiver audio circuits are inoperative and above which signals may be heard. This potentiometer serves co adjust the audio output of the receiver. This

44、 four-position, wafer type switch has the functions tabulated below: PoJition ANT AD DIAL LIGHT- ON Ftmction Turns on calibrate oscil- lator V-7, provided the receiver-transmitter is in the receiving condition. The calibrate oscillator cannot be turned on when the receiver-trans- mitter is m the tra

45、ns- mitting condition. The calibrator oscillator feeds into the receiver r-f stage, a .crystal-con- trolled source of r-f test signal for alining the receiver-transmitter an- tenna circuit. Turns on dial illuminating LAMP ( E-20 1) on the front panel. Turns on the dial illumi- nating LAMP (E-201). D

46、IAL Turns off the dial illumi- LIGHT-nating LAMP. (A load OFF equalizing resistor is substituted for the lamp when the inter- nal TANK-VEH-FIELD switch (S-101) IS in the TANK or VEH position.) CAL Turns on the calibrate os- cillator ( V -7) and 1.4- mc beat oscillator, (part of V-106), to provide a standard test frequency Control or connector ANT connector J-201 ANTENNA TUNING ADJUSTMENT ( C-41) Position J.unction Ftmction a