R.L.DRAKE R-4A, Instruction Manual

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Page 2: ...trol Settings Single Sideband or Double Sideband Suppressed Carrier Reception C W Reception AM Reception RTTY Reception Adjusting Dial Calibration Noise Blanker Operation Operation of Notch Control Accessory Frequency Coverage Fixed Frequency Operation 13 13 13 14 14 15 15 16 17 20 V Theory of Operation 21 A R F Amplifier 21 B First Mixer and Premixer System 21 c Second Converter 22 D 50 KC I F Sy...

Page 3: ...7 Notch Curves Fig 8 Block Dia gram Fig 9 Voltage Chart Fig 10 Resistance Chart Fig 11 Top View Fig 12 Bottom View Fig 13 Schematic Diagram 50KC Oscillator Alignment 50KC I F Alignment Crystal Filter and Filter Match Transformer Alignment 5595 KC Oscillator Alignment Antenna RF and Injection Circuit Alignment 100 KC Calibrator Alignment V F O Adjustment Notch Filter Alignment Passband Tuner Alignm...

Page 4: ...s than 100 cycles for 10 line voltage change SENSITIVITY Less than 5 uv for 10 DB signal plus noise to noise on all amateur bands MODES OF OPERATION SSB CW AM RTTY DIAL CALIBRATION Main dial calibrated 0 to 500 KC and 500 to 1000 KC in 5 KC divisions Vernier dial calibrated 0 to 25 KC in 1 KC divisions CALIBRATION ACCURACY Better than 1 KC when calibrated at nearest 100 KC point AVC Amplified dela...

Page 5: ...pply rectifiers Bias rectifier AM detector Noise blanker pulse clippers Noise blanker gate Switching Prod det FRONT PANEL CONTROLS Main tuning AF gain RF gain SSB CW AM with slow AVC fast AVC or AVC off function switch band switch xtal switch passband tuning and selectivity preselector notch and head phone jack REAR AND SIDE JACKS AND CONTROLS S meter zero notch adjust antenna jack speaker jack mu...

Page 6: ...s as well as the 28 5 MC to 29 O MC portion of 10 meters Ten accessory crystal sockets are provided for coverage of other 500 KC frequency ranges between 1 5 and 30 MC such as 160 Meters MARS frequencies WWV short wave broadcast etc These sockets can be programed to give up to 5 MC of continuous coverage for convenient use with V H F converters The R 4A also includes time proven DRAKE AVC with fas...

Page 7: ...EMENTS The R 4A is supplied with a dual primary power transformer and can be operated from 120 or 240 volt 50 60 cycle AC As supplied from the factory it is wired for 120 volt operation If 240 volt operation is desired it will be necessary to remove the black yellow and black green power transformer primary wires from the terminals to which they are now connected and connect them together at the u...

Page 8: ...ther transmitters having voice control capabilities The impedance at this terminal is approximately 5000 ohms If the transmitting equipment requires a lower impedance it may be necessary to attach a matching transformer between the ANTI VOX terminal on the R 4A and the ANTI VOX input terminal of the transmitter or to use the speaker output G MUTING The Mute jack on the rear of the R 4A is connecte...

Page 9: ...eceiver use lower C a b l e ___ ____ __ R 4 A I Speaker Cable Mute Line _ Receiver Antenna Cable ____ _ _____ p J FIG 1 USING THE R 4A WITH THE TR 4 TRANSCEIVER VIEWING ANGLE OPTIONS FE ET REMOVED O P T I O N 2 __ ___ _ _ INVERTED FRONT FEET FEET REMOVED FROM REAR OF REAR BASE STUD 10x24 x 5 8 L O N G SUPPLIED WITH UNIT FIGURE 2 8 ...

Page 10: ... the normal position crystal selection is accomplished by means of the band switch with the exception of the 1 5 setting When this switch is set on any of the other positions 1 through 10 the crystal inserted in the corresponding crystal socket will be inserted in the circuit for accessory band operation The BAND switch must then be set in ac cordance with the information given on the crystal freq...

Page 11: ... the audio output level of the receiver 8 RF GAIN The R F GAIN knob varies the bias applied to the AVC controlled tubes thus controlling the R F gain of the unit 9 NOTCH The NOTCH control tunes a highly selective notch across the receiver s passband for the purpose of eliminating interfering carriers When turned to the OFF position the Notch is moved out side the receiver s pa ssband Rotation of t...

Page 12: ...he INJ jack provides a means of coupling the premixer system of the R 4A to the T4 or T4X transmitters so that transceive operation with these units can be obtained SPEAKER JACK The SPEAKER JACK on the rear of the chassis is for the connection of a 4 ohm speaker such as our MS 4 MUTE JACK The MUTE JACK is for externally muting and unmuting the receiver The receiver is muted when the FUNCTION switc...

Page 13: ...very rarely For the proper adjustment see operating instructions XTAL VFO SWITCH This switch located on the left side of the chassis allows the operator to select between normal VFO operation or crystal control using a crystal plugged into the CRYSTAL LOCK SOCKET CRYSTAL LOCK SOCKET The R 4A may be crystal locked to a specific frequency by installing a crystal of the required frequency in this soc...

Page 14: ...e main tuning for pleasing audio characteristics If noise is a problem switch the Function switch to N B see function switch and noise limiter explanation If interference from undesired stations is a problem adjust the PASS BAND selector lever to the 1 2 KC position and readjust the PASSBAND knob to the dot at the second line from the top corresponding to the desired sideband A heterodyne from a n...

Page 15: ... receiver gain with the R F Gain control D AM Reception 1 Set the Passband selector lever to 4 8 KC and set the Passband tuning knob to the middle of the longest line 2 Set the SSB CW AM switch to AM 3 Tune in a signal with the main tuning knob Interfering heterodynes can now be eliminated using the Notch control and noise can be reduced or eliminated by turning the Function switch to N B A detail...

Page 16: ...he desired The noise blanker in the R 4A is an I F device which turns off the receiver during a noise pulse It is equally effective on all modes of operation and greatly attenuates most impulse noise For normal operation under no noise conditions the Function switch should be positioned in other than the N B settinq However if noise becomes a problem simply switch to N B It will be noticed that th...

Page 17: ...nd peak the preselector for maximum S Meter reading Advance the Notch control until some reduction in S meter reading is observed Adjust Notch Adjust located on right side of chassis for further attenuation Alternately adjust Notch and Notch Adjust for minimum S meter reading This is the optimum setting for notching and further ad justment should rarely be necessary In order to eliminate an unwant...

Page 18: ...crystals may be ordered direct from the R L DRAKE COMPANY for 5 00 each When ordering be sure to specify that the crystals you desire are for accessory frequency operation in the R 4A In order for the desired band to be received the X T A L Switch must be turnea to the number corresponding to the crystal socket in which the crystal in question is inserted The lowest frequency of the range made ava...

Page 19: ... 4 0 1 0 5 11 o 2 1 6 1 4 0 1 1 0 1 1 5 2 2 1 1 4 0 1 1 5 12 0 2 2 6 1 4 0 1 2 0 12 5 2 3 1 1 4 0 1 2 5 13 0 2 3 6 1 4 0 1 3 0 13 5 2 4 1 1 4 0 1 3 5 14 0 2 4 6 1 4 0 1 4 0 14 5 25 1 1 4 0 1 4 5 15 0 2 5 6 1 4 0 1 5 0 15 5 2 6 1 1 4 0 1 5 5 16 0 2 6 6 1 4 0 1 6 0 16 5 2 7 1 2 1 0 18 CRYSTAL BAND 1 6 5 1 7 0 2 7 6 2 1 0 1 7 0 1 7 5 28 1 2 1 0 1 7 5 1 8 0 2 8 6 2 1 0 1 8 0 1 8 5 2 9 1 2 1 0 1 8 5 1 ...

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Page 21: ...q 21 145KC 5645KC 26 790KC 2 13 395KC crystal frequency A trimmer capacitor is provided directly below the crystal socket for pulling the crystal slightly in order to get exactly on the desired frequency The PRESELECTOR and BAND switch should be positioned as described under Accessory Frequency Coverage for the desired frequency If a T4X is being used placing the T4X TRANSCEIVE switch on SEP CONT ...

Page 22: ...he premixer V8 and the premixer output circuitry composed of T3 and T4 and their tuning and coupling capacitors The VFO signal is applied to the cathode of the premixer V8 and the output of the crystal oscillator Ql is applied to the grid The crystal frequencies are selected so that the difference frequency output of the premixer is 5645 KC above the frequency of the desired incoming signal For ex...

Page 23: ...put of V4 is applied to the grid of the last 12BA6 IF amplifier V 5 through the passband tuner T9 The passband tuner consists of four LC circuits with high Q Passband tuning is accomplished by ganged permeability tuning of the four coils and variable selectivity is accomplished by changing the coupling between the four tuned circuits E DETECTOR SYSTEMS The amplified signal from V5 is applied to th...

Page 24: ...ENCY KILOCYCLES BFO 8 6 4 2 0 2 4 6 8 IO NOTE PASSBANDS A R E CONTINUOUSLY MOVABLE ABOVE AND BELOW EIFO FREQUENCY FIGURE X 6 SELECTIVITY CURVES KILOCYCLES 6 FO 2 I 0 I 2 3 4 5 6 6 0 FIGURE 7 EFFECT OF NOTCH ON 2 4 KC SELECTIVITY CURVE 23 ...

Page 25: ...conds on fa st AVC When the switch is in the AVC off position the load resistor R83 is shorted thus preventing AVC voltage from being developed AVC voltage is applied to the grid of Vl V4 V5 and Noise Blanker IF amplifier V9 Rotating the RF Gain control counter clockwise applies increasingly more negative bias to the AVC controlled tubes thus limiting their gain Adjustment of the receiver sensitiv...

Page 26: ...d a negative pulse causes a large positive pulse to appear at the plate This pulse is applied to the grid of the pulse amplifier Vl0B The 18 K resistor R66 and the 100 K resistor R65 form a voltage divider which applies positive cathode bias to Vl0B and diode D3 preventing both from conducting When a positive pulse is applied to the grid of Vl0B the bias is overcome causing both Vl0B and D3 to con...

Page 27: ...des 10 volts regulated for the VFO and H F oscillator The power transformer has a dual primary As supplied it is connected in parallel for 120 volt operation To operate at 240 volts it will be necessary to remove the GRN BLACK and YEL BLACK wires from their present terminals and connect them together at the remaining terminal of the terminal strip This places the windings in series It will also be...

Page 28: ...est method of finding defective tubes is direct substitution It is best not to rely too heavily on a tube checker D Troubleshooting Careful consideration has been given in the design of the R 4A to keep maintenance problems to a minimum However it is quite possible that some problem will arise which cannot be cured by tube substitution If this occurs we suggest that you either return the unit to y...

Page 29: ...N C Vll OB2 110 N C N C N C 110 N C 7 v12 12BA6 44 0 0 12 6 44 45 l 7 Notes 1 Indicates AC voltage 2 Function switch is in NB position except for V12 measurements where CAL position is used 3 R F and A F gain controls are fully clockwise Side controls are set for normal operation SSB CW AM switch is in Slow AVC position 4 Band switch is on 3 5 and Preselector is peaked on 80 meter noise with ant d...

Page 30: ... 228K 6 5K 9K 12K 16 1K 25K 8 3K 4 5K INF 125K 7 0 2 2K 0 330 0 7 2K 500 0 3 2M 9 1K 8 20K 1 This resistance will vary greatly on various Ohm meter ranges due to the characteristics of diode D3 2 Function switch is in NB position for all but V12 where CAL position is used 3 SSB CW AM switch is on slow AVC and AF and RF Gain controls are fully clockwise 4 All side controls are in their normal opera...

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Page 33: ...ch to CAL 3 Connect a 6 lead to your alignment load and connect it from pin 5 of the 12BA6 V5 to pin 5 of the crystal calibrator V12 4 Advance A F gain control so that an audio beat note can easily be heard 5 Adjust Tll for zero beat Note Do not be concerned that 100 KC calibrator has not yet been set It cannot be pulled far enough off frequency to be of any consequence for this purpose 6 Remove a...

Page 34: ...es wrapped around pins on the base of the crystal filter can T6 Unwrap one of these wires until minimum signal strength is obtained Note Unwrapping the wrong wire will result in an increase rather than a decrease in this signal If much adjustment is necessary here steps 1 through 6 should be repeated D 5 59 5 KC 0 scilla tor Aliqnment 1 2 3 4 5 6 Return Passband selector lever to 4 8 KC and Passba...

Page 35: ... adjust the slugs to this setting This was done at the factory and should be correct Check measurements carefully before altering the position of any of the se slugs Turn on receiver and tune in the crystal calibrator signal at 28 5 mc Set the PRESELECTOR knob so that the slugs are 15 32 above the white sleeves Adjust all four trimmers marked 28 0 for maximum S meter reading If the S meter reading...

Page 36: ...nt If the VFO does not appear to track from one end of the range to the other it should be returned to our plant for alignment Maximum calibration error is 1 KC when calibrated at nearest 100 KC point If you notice the same error from one end of the band to the other and you cannot correct it with the movable dial index the main dial may be slipped on its shaft enough to bring the calibration back...

Page 37: ...ol travel Pointer pointing horizontally to the left and to the right Set the Passband selector lever to the 2 4 KC position and observe the pitch of the noise at the dots at the ends of the second line from the bottom The pitch should be the same at either dot If it is not turn the knob to the left dot and observe the pitch Then rotate the control to the right until the pitch is the same Loosen th...

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