Racal Instruments RA-117 User Manual Download

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Racal RA-117

Radio Receiver

Summary of Contents for RA-117

Page 1: ...Racal RA 117 Radio Receiver...

Page 2: ...25 10 Spurious Responses 26 11 Fault Diagnosis 28 12 Representative Test Data 30 13 General Servicing and Aligment Procedures 32 13 1 General Servicing 33 13 2 Receiver Tests 33 14 Alignment Procedure...

Page 3: ...er 8 First V F O top view 9 First V F O underside 10 Second V F O 11 1 7 Mc s Oscillator Amplifier and Mixer Unit 12 B F O Unit 13 Crystal Calibrator Unit 14 Key to Under chassis Layout 15 R F Attenua...

Page 4: ...A2 reception 30 modulated bandwidth 3 Kc s 3 V for 18dB signal to noise ratio Intermodulation More than 100dB down for interfering signals at least 10 removed from the wanted signal Cross modulation...

Page 5: ...eases the A F output by less than 7dB A V C Time Constants Short Charge 25 milliseconds Discharge 200 milliseconds Long Charge 200 milliseconds Discharge 1 second A F Response With 13 kc s bandwidth r...

Page 6: ...n 6 Dimensions Height Width Depth For rack mounting 10 5in 19in 20 125in fitted dust cover 26 7cm 48 25cm 51cm Fitted cabinet 12in 20 5in 21 875in 30 5 cm 52cm 55 6cm Weight Rack mounted 62 lb 28 kg I...

Page 7: ...igned for both bench table and rack mounting The front panel is painted Light Battleship Grey British Standard Specification 381C colour 697 and has been carefully designed to minimize operator fatigu...

Page 8: ...he receiver can bee provided with alternative sleeves to enable it to be used with a type UR 18 or UR 70 cable or similar cables of nominal diameter 1 2 in or 1 4 in respectively AUDIO OUTPUTS 5 A num...

Page 9: ...con nect T adaptor to socket SKT2 Connect plugs PL12 and PL2 to the T adaptor 2nd V F O input Connect the free plug PL302 to SKT302 2nd V F O output Connect the free plug PL303A to SKT304 1 7 Mc s inp...

Page 10: ...his is indicated by a reduction of signal or noise on either side of the correct setting SYSTEM This switch provides facilities for STANDBY MANUAL A V C CALIBRATION and CHECK B F O BANDWIDTH The two c...

Page 11: ...ble some during the quiet intervals A V C The choice of time constant depends upon conditions The LONG time constant 1 second should be employed with the choice sig nals the SHORT time constant may be...

Page 12: ...a zero beat note is obtained Move the milled cursor slide on the dial escutheon so that the pointer coincides exactly with the selected 100 kc s division 4 Restore all other controls to the prelimina...

Page 13: ...w or voice reception switch B F O off 17 Set the SYSTEM switch to A V C if required 18 Set BANDWIDTH for optimum reception S METER 8 The S meter should be correctly set to zero 9 With no antenna conn...

Page 14: ...circuit These restrict the possible settings to position 1 Mc s apart e g 41 5 42 5 43 5 Mc s etc HARMONIC GENERATOR AND MIXER 5 The output from a 1 Mc s crystal oscillator is connected to a harmonic...

Page 15: ...n the fourth mixer M4 with the 1 7 Mc s output from the 1 7 Mc s oscillator amplifier to provide the fourth and final intermediate frequency of 100 kc s FOURTH I F STAGE 12 The final I F stages are pr...

Page 16: ...llations occurring 30 MC S LOW PASS FILTER 4 The amplified signal is passed to a 30 Mc s low pass filter which has a substantially flat responseover the frequency range L27 C47 and R28 constitute the...

Page 17: ...lifier 9 The output from V1 is capacitance coupled to the harmonic generator V2 and via SK2 to a T adptor for feeding a 1 Mc s input into the L F converter and also the control grid of the mixer valve...

Page 18: ...hassis C107 and the input capacitor of V9 NOTE The anode load of V10 is adjusted to 37 5 Mc s by adjusting the dust iron core in L50 The balancing circuit will be affected if V9 or V10 is changed SECO...

Page 19: ...STAL OSCILLATOR AMPLIFIER 23 The frequency from the crystal oscillator C27 may be set precisely to 1 7 Mc s by adjusting the trimming capacitor C337 The crystal XL300 which is connected between the co...

Page 20: ...at this point by R102 and C173 The screen potential is derived from a potential divider formed by R93 R97 and RV4 This stage is coupled to the second I F amplifier and the I F output stage by a double...

Page 21: ...falls the capacitors C182 and C173 discharge through R118 R127 and L81 into the diode load resistor R116 The A V C potential is brought out via R123 to the tag strip at the rear of the receiver for e...

Page 22: ...the V F O switch S300 is set to the INT position 42 The 1 Mc s signal fed through SK2 is connected through PL2 and the grid stopper R83 to the first grid of the mixer valve V13 The anode load consists...

Page 23: ...nnected to the R F I F GAIN control RV1 by S5E 3 a 2 a and 2 b are applicable b S5D connects the A V C line to the A V C diode 4 a H T is applied via S5A S5B and S5F to all stages except The R F ampli...

Page 24: ...Detailed Circuit Description 24 at maximum is the correct calibration maintained...

Page 25: ...manual 1 Valve voltmeter reading up to 10V at frequecies up to 70 Mc s 2 Signal generator capable of operating on fundamental frequencies up to 40 Mc s 3 Digital frequency meter measuring frequencies...

Page 26: ...eak through CHECKS FOR SPURIOUS RESPONSES 3 Spurious responses are measured relative to receiver noise in the following manner When response is located the receiver is de tuned from it just sufficient...

Page 27: ...onses may occur at 4 5 5 5 and or 17 5 Mc s if C42A and or C194A are open circuit These responses are caused by the harmonics of the first v f o breaking through to the second mixer stage and beating...

Page 28: ...ixed capacitor can be selected the input capacitance of the valve voltmeter must be know If the trimmer is used this should be connected across a capacitance bridge and set to the required value FAULT...

Page 29: ...the gen eratorto socket SKT11 and set generator to a frequency of 2 5 Mc s approximately and tune for maximum deflection on the meter The sensitivity should be better than 250 V for 100 A 11 Set the...

Page 30: ...xer level crystals TP3 2 5 Mc s c w 25 V 100 A R F re inserted level V F O switch set 2 9 Mc s c w 25 V level 100 A R F to INT Image response i e receiver frequency plus 200 kc s should be at least 60...

Page 31: ...Representative Test Data 31 2 volts h The level of the 37 5 Mc s drive at TP3 should be between 2 and 10 volts at any MEGACYCLES setting...

Page 32: ...32...

Page 33: ...er meter 3 Signal generator 4 Multimeter 13 2 Receiver Tests RECEIVER OVERALL GAIN TESTS C W 6 Perform a sensitivity test as follows 1 Set the controls on the receiver as follows R F RANGE 2 4 Mc s ME...

Page 34: ...enna input socket 4 Tune the receiver to the output frequency of the signal generator and adjust the R F I F GAIN control a reading of 50mW on the output meter 5 Switch off the input signal and check...

Page 35: ...t the A F LEVEL control until the meter reads exactly 10mW Check that the external output meter reads within 1dB of 10mW NOTE It is important that the A F LEVEL control is not turned towards its maxim...

Page 36: ...ator output level control until a reading of 20mW is ob tained on the output meter 9 The noise factor of the receiver is given by the noise generator meter reading for the range in use 10 Perform nois...

Page 37: ...cross L73 Adjust C171 for maximum indication Remove the 4 7 kilohms resistor The signal generator output required to produce a 100 A deflection should be approximately 800 V Tune the signal generator...

Page 38: ...ncy is not greater than 100 900 c s Tune through the passband adjusting the signal generator output as necessary to avoid meter damage Note the highest frequency at which a signal generator output equ...

Page 39: ...e 1000 kc s position 8 Lock the drive sprocket 9 Adjust the position of the film scale to produce a correct calibration NOTE When moving film scale relative to the sprockets grip both sides of the fil...

Page 40: ...that order several times to obtain maximum output The input required to produce 1V should be approximately 2 5mV The 6dB bandwidth of the 37 5 Mc s chain should lie between 229 300 kc s The bandwidth...

Page 41: ...N MAX 37 Remove the screening cover from around C18A B and connect a 1 kilohm resistor across the secondary section C18B rear section Set the R F TUNE control approx imately 7 8ths of its travel in a...

Page 42: ...major fault be suspected or if L70 or L75 have been inad vertently mis aligned it will be necessary to remove the unit and make up an extension cable so that the unit may be operated outside the recei...

Page 43: ...F transformer and cores L313 L314 in the second I F transformer for a maximum reading on the valve voltmeter 52 Check the gain of the I F amplifier as follows 1 Connect the signal generator to SKT301...

Page 44: ...18 f Detector and noise limiter V21 g 100 kc s output V17 5 Crystal Calibrator V13 and V15 6 Main Chassis a Aerial antenna attenuator b Crystal oscillator amplifier V1 c Harmonic generator V2 d 30 and...

Page 45: ...5 Key to Under chassis Layout 3 Remove the front panel see para 2 above 4 Withdraw the Crystal Calibrator Unit by slackening the two knurled nuts dis connecting the coaxial cable and unplugging the un...

Page 46: ...der very light tension onto the bobbin until the sprocket holders in the film engage with the tuning drive sprocket 3 Maintain the STOP marking approximately in the centre of the escutcheon win dow an...

Page 47: ...unit 4 Remove the six screws securing this unit to the main chassis NOTE Removal of the R F I F GAIN control on the B F O assembly is necessary in order to obtain acces to one of the six securing scr...

Page 48: ...hree screws securing this unit to the main chassis 5 Re assemble in the reverse order Valve Replacement 12 With the exception of V5 replacement of valves will not affect receiver alignment When V5 is...

Page 49: ...0 R13 33Kohm carbon 1 4W 10 R14 150ohm carbon 1 4W 10 R15 100ohm carbon 1 4W 10 R15A 75ohm carbon 1 4W 10 R15B 2 2Kohm carbon 1 4W 10 R16 680ohm carbon 1 4W 10 R17 1Kohm carbon 1 2W 10 R18 470ohm carb...

Page 50: ...0 R48 10ohm carbon 1 4W 10 R49 68ohm carbon 1 4W 10 R50 2 2Kohm carbon 1 4W 10 R51 1Kohm carbon 1 4W 10 R52 15Kohm carbon 1 4W 10 R53 470ohm carbon 1 4W 10 R54 100ohm carbon 1 2W 10 R55 1Kohm carbon 1...

Page 51: ...n 1 4W 10 R88 330ohm carbon 1 4W 10 R89 2 2Kohm carbon 1 2W 10 R90 4 7Kohm carbon 1 2W 10 R91 4 7Kohm carbon 1 2W 10 R91A 470Kohm carbon 1 4W 10 R92 270Kohm carbon 1 4W 10 R93 33Kohm carbon 1 2W 10 R9...

Page 52: ...R125 47Kohm carbon 1 4W 10 R126 100ohm carbon 1 4W 10 R127 82Kohm carbon 1 4W 10 R128 18Kohm carbon 1 4W 10 R129 18Kohm carbon 1 4W 10 R130 82Kohm carbon 1 4W 10 R131 4 7Kohm carbon 1 4W 10 R132 1Koh...

Page 53: ...bon 1 4W 10 R313 100ohm carbon 1 4W 10 R314 56ohm carbon 1 4W 10 R315 470Kohm carbon 1 4W 10 R316 100ohm carbon 1 4W 10 R317 2 2Kohm carbon 1 4W 10 R318 220ohm carbon 1 4W 10 R319 10Kohm carbon 1 4W 1...

Page 54: ...er Mica 350V 10 C11 0 005 F Paper 400V 20 C11A 47pF Silver Mica 350V 5 C12 14 7pF Ceramic 750V 10 C13 14 7pF Ceramic 750V 10 C14 0 01 F Paper 500V 20 C15 10pF Ceramic 750V 5 C16 0 01 F Paper 500V 20 C...

Page 55: ...r 150V 25 C42 220pF Silver Mica 350V 5 C42A 0 001 F Ceramic 350V C43 16pF Trimmer 1000V with acetate case C44 39pF Silver Mica 350V 5 C45 16pF Trimmer 1000V with acetate case C46 33pF Silver Mica 350V...

Page 56: ...Trimmer 1000V with acetate case C71 39pF Silver Mica 350V 5 C72 16pF Trimmer with acetate case C73 33pF Silver Mica 350V 5 C74 220pF Silver Mica 350V 5 C75 220pF Silver Mica 350V 10 C76 100pF Variabl...

Page 57: ...1 0 05 F Paper 350V 25 C102 0 001 F Ceramic 350V C103 0 1 F Paper 150V 25 C104 0 001 F Ceramic 350V C104A 0 25 F Paper 150V 25 C105 0 01 F Paper 500V 20 C106 0 001 F Ceramic 350V C107 220pF Silver Mic...

Page 58: ...r 350V 25 C142 DELETED C143 DELETED C144 DELETED C145 6800pF Silver Mica 350V 5 C146 270pF Silver Mica 350V 2 C146A 100pF Ceramic 350V 2 C147 70pF Trimmer 12 vane with acetate case C148 70pF Trimmer 1...

Page 59: ...0V 5 C170A 33pF Silver Mica 350V 5 C171 70pF Trimmer 12 vane with acetate case C172 120pF Silver Mica 350V 5 C173 0 1 F Paper 150V 25 C174 0 05 F Paper 350V 20 C175 33pF Ceramic 750V 5 C176 0 1 F Pape...

Page 60: ...2 39pF Silver Mica 350V 2pF C203 22pF Ceramic 750V 5 C204 0 1 F Paper 150V 20 C205 0 001 F Ceramic 350V C206 32 32 F Electrolytic 350V C207 0 05 F Paper 350V 20 C208 0 05 F Paper 350V 20 C208A 0 01 F...

Page 61: ...immer C236 22pF Trimmer C237 22pF Trimmer C300 4 7pF Ceramic 750V 1 2 C301 220pF Silver Mica 350V 5 C302 0 01 F Paper 500V 20 C302A 0 01 F Paper 500V 20 C303 15pF Ceramic 750V 5 C304 0 01 F Paper 500V...

Page 62: ...0V 5 C328 53pF Silver Mica 350V 2 C329 0 005 F Paper 250V 20 C330 0 001 F Silver Mica 350V 5 C331 155pF Silver Mica 350V 2 C332 100pF Silver Mica 350V 5 C333 DELETED C334 100pF Silver Mica 350V 5 C335...

Page 63: ...Pentode CV4009 6BA6 V17 Pentode CV4009 6BA6 V18 Double Diode CV4007 6AL5 V19 Pentode CV4010 6AK5W V20 DELETED V21 Double Diode CV4007 6AL5 V22 Output Tetrode CV4019 6AQ5 V23 Double Triode CV4024 12AT7...

Page 64: ...p anode L28 Coil assembly 37 Mc s mixer anode L29 40 Mc s filter L30 37 5 Mc s filter L31 40 Mc s filter L32 37 5 Mc s filter L33 Coil Assy 37 Mc s Amp Anode L34 40 Mc s filter L35 37 5 Mc s filter L3...

Page 65: ...age L72 L73 100 kc s I F first stage L74 L75 0 9 Mc s anode coil L76 I F output Transformer assy L77 L78 100 kc s final stage L79 L80 Smoothing choke L81 150mH choke L82 B F O coil L83 Filter coil Ant...

Page 66: ...ectifier MR5 Rectifier MR6 Rectifier MR7 Rectifier Loudspeakers LS 2 1 4 inch square 3 ohm Meter M1 200 micro amp Crystals XL1 1 Mc s 0 005 XL2 99 964 c s 0 005 XL3 99 890 c s 0 005 XL4 DELETED XL5 10...

Page 67: ...hode Anode2 Grid1 Cathode1 Grid1 2 Cathode Grid2 Cathode Grid3 Grid1 Grid2 Cathode Anode2 Cathode Grid3 Grid5 Grid3 3 Heater Cathode2 Heater Heater Cathode Cathode2 Heater Heater Heater 4 Heater Heate...

Page 68: ...F amplifier V15 220 5 110 6 6 5 7 6BA6 EF93 Calibrator V16 180 5 88 6 1 46 7 6BA6 EF93 Second I F amplifier V17 150 5 92 6 1 36 7 6BA6 EF93 I F output V18 27 0 1 6AL5 EB91 A V C and T C V19 155 5 110...

Page 69: ...ier and Mixer Unit 12 B F O Unit 13 Crystal Calibrator Unit 14 Key to Under chassis Layout 15 R F Attenuator 16 Supply Filters 17 Crystal Oscillator Amplifier and Harmonic Filter System 18 Second Mixe...

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Racal Instruments RA-117, User Manual

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