DRAKE SPR-4 Spécifications

DRAKEMODEL SPR-4COMMUNICATIONSRECEIVERTECHNICAL MANUAL

The SPR-4 audio amplifier may be used with an external audio sourcesuch as a tuner. The level of the external source must be approximately.08 volts in

a,

3. OPERATIONRefer to Figure 3 for the location of the operating controls.3.1 OPERATING CONTROLS1.2.3.4.5.6.7.8.9.10.TheS-meter indicates the relative

knob from the off position moves the rejection notch across the re-ceiver pass band .11. The accessory switch turns on the S-NB Noise Blanker and the

.;-13-

4. PRINCIPLES OF OPERATION4.1 LOOP AM PLIFIEROn Bands A and B , Q1 amplifies signals from the loop antenna and feedsone gate of the R.F. amplifier Q4,

to one gate of the premixer, Q5 through C26 and R15. The P.T.O. drivesthe other gate of Q5 through R25 and C76. The P.T .O. is tuneable from4955 kHz t

4.9 AVC SYSTEMThe AVC threshold is established by the setting of R111, the R.F. gaincontrol.R111 is normally operated fully clockwise . This applies a

-17-

Table of Contents1. GENERAL DESCRIPTION1.1 Features1.2 Specifications112. INSTALLATION52.1 Unpacking52.2 Location52.3 Power Requirements52.4 Antennas5

-18-

5.ALIGNMENT5.1 REMOVING COVERSRemove the AL-4 Loop Antenna if it is in use.Remove the top three screwson each side of the SPR-4 and remove the top cov

4. An accessory crystal for reception of WWV standard frequency trans-mission that is most reliably received in your area.See Page 33 to determine cry

minal on the R.F. amplifier board at the left top corner, looking intothe bottom of the SPR-4 and front pane1 facing you. This terminalhas coax connec

and mixer trimmers for maximum AVC deflection. Detune T6 by grasp-ing a metal screwdriver shaft and touching it to the rotor contact ofS4R, and tune t

the notch control at 12 o’clock and adjust the main tuning knob for max-imum AVC voltage ( positive going ) .Altemately adjust the notch controland th

6.16.1.16. ACCESSORIESMCDEL SCC-4 CRYSTAL CALIBPATORGENERAL DESCRIPTION6.1.26.1.3The SCC-4 is a 100 kHz crystal controlled oscillator that injects int

puls e. Between noise pulses ,full receiver gain is restored . ReceiverAVC is affected only by the desired signal and not by noise when the5-NB is in

reverse biased and turned “off”. With the series gate “off”, the signalpath through the 5-NB is broken and reception is blanked for the dura-tion of t

6.3.2When the mode switch is in the AM or USB position, shorting the RTTYjack will have no effect.INSTALLATIONThis modification should be made by a co

1.11.21.2.11. GENERAL DESCRIPTIONFEATURESThe SPR-4 is an a11 solid-state communications receiver which can teprogrammed with accessory crystals to cov

6.3.4CIRCUIT DESCRIPTIONThe BF0 is shifted in frequency for RTTY reception by shunting a capacitoracross T17 with an electronic switch .Transistor Q2

pins .Late SPR-4’s have a 12 K 1/2 watt resistor between T-6 and the pre-mixer board . Cut the resistor lead from T-6 and remove the resistor. Routeth

6.4.4 CIRCUIT DESCRIPTIONThe transceive switch on the T-4/T-4B/T-4X/T-4XB Transmitter controlsthe TA-4 by applying a negative or positive D.C. potent

6.5 AVC ALTERATIONSCONTROL OR SWITCHBand or Range switchCrys tal switchFunctionModeAudio GainTransceiveAnti -VoxS idebandPreselectorS PR-4T-4XBD 3.53.

6.5.3 AVC OFF ALTERATIONThe AVC may be remotely turned off in SPR-4’s with serial numbers above1,000. This is obtained by altering connections to two

SPR-4 ACCESSORY CRYSTAL CHARTOPERATING FREQ. CRYSTAL FREQ . OPERATING FREQ. CRYSTAL FREQ.in MHz. in MHz. in MHz. in MHz..15 .5*None Required-26.09-. 1

6.6 SERVICE DATA FOR SPR-4 ACCESSORIESSCC-4 D.C. and R.F. VOLTAGE CHARTTransistor Drain Collectr Source Emitter Gate BaseQ1 3.3(3 v) 3.0.8Q2 6.2(670mV

Note:All componentson this board arenot shown.-JUMPER TO THIS LEAD“SEE TEXT”,‘^...0-” ,!RY-4 CALIBRATION CONNECTION TO SPR-4Figure 8+3 220* ‘“‘“-L“”c4

5-NB D.C. AND R.F. VOLTAGE CHARTTransistorQlQ3Q4Q6Q8Q10Q11Q12Q13Q14Q15Q16Drain Collector12.1 (31) 2.7Q2 2.6 2.48.5(3.4V) 3.43.1(9.4) 1.8 (

1.2.21.2.31.2.4Audio Output Power: 3 watts into 4 ohm load (less into higher imped-ance loads ).Hum and Noise: More than 60 dB below rated output.Cali

L-

TransistorCollectorEmitter BaseQ1,CW -1.4 8.8 8.7Ql, LSB -1.1 8.8 8.7Q2,,CW 29 2.2 -. 3Q2,LSB 30 2.2 -. 3Q3,,CW 33 2.2 -. 5Q3,LSB 33 2.2 -. 5MEASURE

S\4R Q1-\tA---R3TO EMITTER Q27R4 C3.l+AQ3Figure 15 RY-4 Schematic Diagram-41-

INJECTIONANTI-VOXTA4 CIRCUIT BOARD INSTALLATION DIAGRAMFigure 16PWR SUPPLY AND AGC~- ~~TA-4 PICTORAL WIRING DIAGRAMFigure 17- 42 -

TA-4 D.C. VOLTAGE CHARTTransistor Transceive ModeCollectorEmitter BaseQ1 Separate ----- 0.0 0.7Q1 Transmitter -----0.0 0.7Q2 Separate 0.050.0 0.6Q2 Tr

2Ni394-TA-4 CIRCUIT BOARDFigure 18- 44 -

YELLOW TO CENTER TAP T-6rTA4 SCHEMATICFigure 19- 45 -

SPR-4 D.C.VOLTAGE CHARTTransistor Drain CollectorSource Emitter Gate 1 Base Gate 2Q17.3Q29.0Q3PT0Q49.7Q59.8Q6PT0Q710.2Q810.2Q917.0Ql011.8Qll6.3Ql212.2

SymbolCRlCR2CR3CR4CRSCR6CR7CR8CR9CRl0CRllCR12CR13CR14CR15CR16CR17CR18CR19CR20CR21TypelN270lN4148lN4148lN714B5G5B5G5B5G5Z13BlN714lN4148lN270lN4148lN414

SPR-4 R.F.VOLTAGE CHARTTrans is torQ1Q4Q7, Q8Q10Q23Q24Q5Q11Q17Q21Q27FunctionLoop AmpRF Amp1st Mixer2nd Mixer1st IF Amp2nd IF AmpRange Xtal Osc.Premixe

2N 3394 MFE 3007*SFC4982@tg*2N 5949TIS889*2N 5950*2N 52458 5030*2N 52462N 4125 2N 3566CA 3053* SERIAL NO'S ABOVE 1000TRANSISTOR LEAD CONFIGURATIO

TERMINAL(PC SIDE)LOOP ANTENNA CIRCUIT BOARDFigure 22- 50 -

- 51 -

a- 53 -

- 54 -

VIEWING ANGLE OPTIONSFigure 1.- 4 -

!..

R5720K POT

Cl41c?.o*82

RW

--62--

2. INSTALLATION2.1 UNPACKINGCarefully remove the receiver from the shipping carton, and examine itfor evidence of damage. If any damage is discovered,

50 to 100 feet long will give good results .An antenna kit (Mode1 AN-S)is available.For best single band performance,a half wave dipole or other reson

2.8.1 POWERThe power connector mates with both the AC and DC power cords .See“2 . 3 ”2.8.2 FUSEThe fuse holder must have the proper fuse installed for