SERVICE MANUAL FOR GENERAL RADIO SERVICE MODEL GRS
Contents
1. Ignition noise exists because each of the spark plugs in the engine is small but potent spark transmitters which are still fondly remembered by old time hams and ship radio operators In addition there is another spark transmitter under the distributor cap A very high potential pulse ranging from 10 000 volts to 20 000 volts is generated every time the distributor points open The points shown in Fig 1 are opened and closed by a cam at a rate determined by the speed of the engine When the points close DC flows from the vehicle s battery through the ignition switch SI distribu tor points and the primary winding of the ignition coil setting up an intense magnetic field which envelopes the ignition coil secondary When the points open the DC flow in the primary winding ceases abruptly causing the magnetic field to collapse and inducing a potential in the secondary winding of the ignition coil The e m f induced in each turn is in series aiding with the e m f in the other turns The high voltage results not only because of the very high turns ratio of the windings in the ignition coil but because of the sharp magnetic kick caused by sudden cessation of current flow through the primary The ignition coil turns ratio ranges from 40 1to 100 1 As a straight transformer CRUE RD Page 11 MODEL GRS 1566 GENERAL RADIO SERVICE EQUIPMENT SUFFR SICN Continued Wach of these gaps looks2. a border around the individual decal for each heading 2 Dip decal in water for a few seconds 3 Slide from backing and into position 4 Remove air bubbles with soft rubber squeegee Allow to dry Page 7 MODEL GRS 1566 GENERAL RADIO SERVICE EQUIPMENT CONVERSION of 12VDC 117AC to 6VDC 117AC Step 1 Disconnect green wire at pin 7 of Pl and connect to Point A Connect yellow wire taken from Point A to Pin 7 of Pl Step 2 Disconnect blue wire at Pin 10 Pl or feedthru C63 and connect to Point B Connect red yellow wire taken from Point B to Pin 10 Pl Step 3 Disconnect black wire at Pin 5 of V1 Point C Note black wire is on Pin 5 of P1 and connect to Pin 9 of VI Point D Ground Pin 5 of V1 Point C by connecting jumper wire to center shield of socket Step 4 Remove shield on VIB socket use jumper wire 16G to connect Pin 2 to Pin 4 Step 5 Remove 12V DC marking at rear of chassis mark at 6V DC Point OPERATING PROCEDURE To place the set in operation rotate the volume control in a clockwise direction and set the channel switch in position A or other channel known to be ready for operation After the set warms up about 30 seconds rotate the squelch control in a counter clockwise direction and the volume control in a clockwise direction until noise or signals are heard Set the squelch control as follows rotate control in a clockwise direction while there are no signals on the air until t
3. adapter and trim to 3 8 Bare 5 8 of conductor Tin exposed centre conductor Screw plug sub assembly part of 83 1SP on adapter Solder braid to shell through solder holes Use enough heat to create bond of braid to shell Solder conductor to contact For final assembly screw coupling ring on plug sub assembly Page 6 MODEL GRS 1566 GENERAL RADIO SERVICE EQUIPMENT HOW TO ASSEMBLE ANTENNA CONNECTOR to coaxial RG8 U lead in cable 6 Thread cable into connector shell at b threaded inner wall of connector shell grips into cable pro viding extra strain relief Cable should be seated on connector shell so that shielding meets vertical inner wall of connector at d Conductor should extend to end of pin contact at f Small tooth 1 Cut end of cable even e seats in slot edge of Coax Receptacle 2 Remove vinyl jacket 1 7 Solder connector shell to shielding through holes 3 Remove 13 16 of metallic shield provided at c Fill pin contact with solder 4 Bare 3 4 of conductor 8 Bring back coupling ring a over connector shell 5 After stripping disassemble connector plug and and screw on for full length of coupling ring inner slide coupling ring a over cable thread INTERNAL ADJUSTMENTS When crystals are installed at the factory the equipment is tuned so that the station licensee may perform installation and initial tuneup without technical supervision When so installed the set will perform satis
4. like a very high impedance until the dielectric air or vapor breaks down and an arc is formed across the gap Then each gap looks like a low impedance and for the very short duration of the spark the current flow is large and a magnetic field is developed around the ignition wires Thus we have a spark transmitter whose resonant frequency is determined by the inductance and capaci tance of the ignition circuitry SUPPRESSORS A high voltage is required to cause a spark to jump across a gap the current can be infinitesimal For this reason we can reduce the current to reduce the noise radiating field without reducing the effective voltage Even if a 1 meg ohm resis tor R1 is connected in series with the spark gap as shown in Fig 3A the source voltage El will be equal to E3 the voltage across the gap There will be no voltage E2 across R1 because there is no current flow before the gap breaks down and is arced across But this ideal gap condition does not exist As shown in Fig 3B there may be leakage resistance across the gap dirty spark plugs This leakage resistance R2 is in series with R1 and the voltage applied to the spark gap E3 is equal to the voltage El minus E2 It is for this reason that the distributor suppressor is usually a 7500 10 000 ohm resistor and each spark plug suppressor has a resistance of about 5000 ohms The total 15 000 ohm resistance in series with the two gaps distributor and one spark plu
5. of S 2A GENERAL RADIO SERVICE EQUIPMENT PART NO 69155 69147 69125 69185 69173 69331 69549 69165 69169 69160 69173 69173 69185 69170 69170 69173 69167 69165 69165 69152 69180 69161 69173 69140 69151 69161 69165 69123 69159 69145 69165 69149 69359 69145 69165 69129 69159 69145 69129 69159 69145 69173 69173 69155 69157 69520 69718 69718 69273 29137 75303 75303 BS Qaror sy U 055 3 555 65 68 Co O pu pe lt lt lt lt lt lt lt lt lt lt lt lt lt lt lt lt e ERTTIT SOT GN lt DESCRIPTION TRANSFORMERS Trans audio output 5500 to 3 2 ohms Trans power Primary 117v AC 5 amp 12v DC 4 5 amp 6 DC 10 amp Secondary Output over joue doubler 270v DC at 100 MA ELECTRON TUBES XMTR osc Noise amp PWR amp Audio driver Squelch RCVR audio output XMTR mod Noise rect Mixer AVC gate Noise limiter Det Squelch rect R F Mixer RCVR osc 18 IF 2nd IF MISCELLANEOUS PARTS 6 amp fuse for 12V DC 15 amp fuse for 6V DC 1 amp fuse for 117V Relay Speaker 3 2 ohm 5 x 3 Meter Vibrator 6 volt PART NO 80031 82101 12AV1 2 12AV7 2 6AQ5 12AX7 2 12AX17 2 6AQ5 6AL5 2 6AL5 2 68 9 68 7 3 68 7 3 6U8 2 6 8 2 6BA6 42112 42113 42114 66002 73100 48001 88100 GNIBHOLM INDUST PORT MO DWG No 37 1566 PROJECT 1566 685 PHONE SCH
6. 0 15678 15214 15214 15215 15215 29136 29137 29129 24400 24405 24402 24403 24404 24409 24109 24408 24405 81215 81215 81215 24405 24400 24406 1N295A 63001 63001 21401 21402 21425 99207 99208 59503 69157 69157 69145 69153 69153 69125 69143 Page 16 MODEL GRS 1566 REPLACEABLE PARTS REF SYMBOL we Q2 O2 5 RO PO 62 PO tO RO RO 62 PO PO PO 2 Ea EE EE Ha P3 CO OO SEO UP OQ IP ODO9o RcRBGO TOUADARGUUUDEACUTUTU OTRAS Se R 33 R 51 R 55 DESCRIPTION RESISTORS Cont d 33K ohms 1 2w 10 See Controls 6 8K ohms 1 2w 10 See Controls Same as R 6 10 meg ohms 1 2w 10 1 meg ohm 1 2w 10 330 ohms 1w 10 10K ohm 2w 10 220K ohm 1 2w 10 470K ohm 1 2w 10 82K ohm 1 2w 10 Same as R 14 Same as R 14 Same as R 13 560K ohm 1 2w 10 Same as R 22 1 Same as R 14 330K ohm 1 2w 10 Same as R 17 Same as R 17 18K ohm 1 2w 10 3 9 meg ohm 1 2w 100K ohm 1 2w 10 Same as R 14 1 8K ohm 1 2w 10 15K ohm 1 2w 10 Same as R 29 Same as R 17 68 ohm 1 2w 10 68K ohm 1 2w 10 Same as 8 3 Same as 8 17 10K ohm 1 2w 10 68K ohm 1w 10 Same as 8 9 Same 85 17 Same as 46 Same as R 36 Same as R 3 220 ohm 1 2w 10 Same as R 36 Same as R 3 Same as R 14 See Controls Same as R 14 Same as R 8 Same as R 1 39 ohm 2w 10 200 ohm 5w 10 wire wound Same as R 55 1 meg ohm 1 2 w 20 0 SWITCHES Part of R 11 Band switch Part
7. 000000000000000000000000000000000 2522020205 565 22 2 6 6 En En 6 En En En 6 4 o RROD CO Co CO 3 CO CO CO RO BO TQ RO TO RO DO RO PO 62 58558855 55 6000000000000000000000 EO Qoo Rm CO 6 uon ve PART DESCRIPTION NO CAPACITORS Ceramic 10 mmf 500v N330 f 5 15130 Ceramic 15 mmf 500v N080 75 15132 Mica 100mmf 500v 5 15417 Ceramic 15 mmf 500v NO80 2 5 15132 Same as C 3 15417 Mica 33 mmf 500v 5 15416 Ceramic 002 mf 100v 10 15176 Ceramic 01 mf 500v Z5U 80 20 15137 Same as C 7 15176 Same as C 7 15176 Air variable 3 14 2 mmf 18112 Ceramic 5 6 mmf 500v NO80 5 16134 Same as C 12 15134 Mica Trimmer 110 580 mmf 18113 Ceramic 2 2 mmf 500v NO80 2 5 15135 Mica 22 mmf 500v 5 15422 Same as C 3 15417 Same as C 22 15419 Same as C 8 15137 Same as C 7 15176 Same as C 7 15176 Mica 47 mmf 500v 2 5 15419 Same as C 8 15137 Same as C 8 15137 Electrolytic 5 mf 50 v 15201 Same as C 27 15109 Ceramic 001 mf 500v Z5U 10 16109 Not used Electrolytic 50 mf 25v 15216 Ceramic 005 mmf 1KV 100 0 15177 Same as C 8 15137 Ceramic 08 mf 100v 80 20 15140 Mica 200 mmf 500v 5 15420 Same as C 3 15417 Same as C 3 15417 Same as C 33 15420 Molded mylar 1 mf 200v 20 15673 Ceramic 22 mmf 500v N080 5 15161 Same as C 6 15416 Same as C 37 15673 Same as C 8 15137 Same as C 8 15137 Same as C 8 15137 Same as C 2 15132 Mi
8. 43 toground The METER ZERO control R 9 is set to zero reading with no signal with signal the effective cathode screen resistance changes directly as the AVC voltage varies This unbalances the bridge to give a reading which varies approxi mately as the signal varies CIRCUIT DESCRIPTION TRANSMITTER The transmitter is a master oscillator power amplifier circuit with crystal control ofthe operating frequency The oscillator stage uses one triode section of a 12AV T in a Colpitts circuit The oscillator plate tank L 2 C 4 is tuned to the channel frequency while the grid circuit operates at one half the channel frequency The RF developed across the plate tank drives the grid of the power amplifier tube V 2 a type 6AQ5 The plate of V 2 is tuned to the channel frequency by a pi section net work consisting of L 4 antenna loading capacitor C 14 and the power tuning capacitor C 11 The power amplifier operates class C with grid bridge neutraliza tion Rice system Capacitor C 12 is the neutralizing capacitor L 5 and C 17 t gether with a portion of the loading capacitance C 14 act as a second pi network which is fixed tuned to reduce possible radiation of harmonic frequencies above the highest channel The output from the second filter is fed to the antenna through one set of contacts of the antenna transfer relay K 1A The meter rectifier CR 1 rectifies a small portion of the RF voltage developed across the output loading ca
9. D SERVICE MANUAL FOR GENERAL RADIO SERVICE MODEL GRS 1566 D O T Approval No C S A Approval No 137361026 p LR 19921 Frequencies Electrical Ratings Range 27 005 27 225 117v AC 5 amp 60 cycle IF 455 Kc 12v DC 4 5 amp 6v DC 10 amp NOTICE RE PARTS ORDERING In order to assure correct parts shipped please supply the following information 1 Chisholm part number of part 3 Model number of set from Manual 4 Date set was purchased and the 2 Serial number of set colour Your parts guarantee will be effective only when the parts warranty registration card is filled out and mailed to the factory within ten days of original purchase DEALER S NAME ADDRESS 90 DAY PARTS WARRANTY NOTE All general radio service crystals have a different correlation factor Therefore all crystals used in the GRS 1566 set should be CIL crystals purchased from Chisholm Industries Limited TABLE OF CONTENTS Page No Description Power Supply and Control Circuits 2 Circuit Description Receiver 2 Circuit Description Transmitter a Antenna and Antenna Structure Requirements Installation Procedure How to Assemble Connector RG58U and RG8 U Internal Adjustments Tuneup on other Channels Conversion of 12VDC to 6VDC Operating Procedure Service Tuneup Parts Locations and Diagram Suppression Engine Noise 10 11 12 13 14 Parts List 15 16 Schematics 17 ur A
10. E diez m ee ee os Page 13 MODEL GRS 1566 GENERAL RADIO SERVICE EQUIPMENT BONDING AND SHIELDING If all of these measures do not reduce noise adequately try bonding the hood to the firewall and the tail pipe to the car s frame using one half inch wide tinned copper braid It may also be necessary to shield the leads between the regulator and the generator grounding the shield to the generator frame Or existing wires may be replaced by shielded cable with inner conductors of adequate size and insulation for the voltage to be carried Tire static may be eliminated by blowing static powder G C and other brands into the tires using the injector provided with the kit Wheel noise can be eliminated by installing springs under the hub caps to ground the axle to the wheel Such springs are available at radio parts jobbers If all these measures fail to reduce noise to a sufficiently low level a shielded ignition system can be installed Available in kit form from Hallett and others the system includes shielded cables to replace all the ignition wiring plus shields for the ignition coil distributor the spark plugs and the regulator A kit for a typical car is available from those of the larger electronic parts dealers who have industrial departments Such shielded systems are widely used in military and public safety vehicles To determine if your car needs noise suppression or to determine if the elimina tion methods have been effect
11. EMATIC DIAGRAM EI 552587 eine ova Ra NOT SCALE THs Dow VA v2 12AV7 2 SAQS XMTR OSC ce PWR AMP i d 2 L1 cay EE 4 vu on s 83 AW 9 eX E AUDIO DRIVER REVRAUDO a ET MODULATOR c24 L7 2 RN i RI7 C27 26 20 ji loe 812 d CARBON I IC mal TS RIG Ar J yen 4 4 auk PUSH TO TALK l a I es V7 68 6 43 RF ass 1 Lo eT cal 838 R37 lg ca 29 I RCVR OSC RSI A detur 1 4 f L4 gt eis 4 o FU 68373 LIMITER 12 VOLT GAMP 6 VOLT 15AMP wa 1 5 f HOT Fa 124x7 2 ape GND SQUELC H ime VEHICLE 45 7 ra 60cPs art H n ue 7 vec 6BJ7 3 SQUELCH RECT R50 ars BLK T2 _RED age R56 82 4 EN AMP ces les Yn 72 F2 jen Li x GREEN RE 1 nt per czol gt
12. Gar EBLON d P
13. S 1566 GENERAL RADIO SERVICE EQUIPMENT SERVICE TUNEUP Model GRS 1566 The unit comes factory tuned to one of the channels near the middle of the band see paragraph on internal adjustments Re tuning on specific operating frequencies may improve performance in some cases particularly if the channels used are at one end on the band The transmitter tuneup procedure is as follows 4 Tune L2 for maximum output 2 Adjust power tuning control for maximum meter reading 3 Plate voltage of V2 typical 210 v should be measured by placing service voltmeter between J1 black pin jack located on chassis backplate and chassis ground Then check plate current of V2 by placing the service voltmeter across 1 and J2 reading the voltage drop typical 2 4 v through R6 100 ohms Calculate the plate current flow through R4 The plate power input to the final amplifier can then be calculated P El If plate power input is 5 watts no further internal adjustments are needed in the transmitter section If power input must be changed reset C14 by rotating clockwise or counter clockwise by a small amount and then repeat steps 1 2 and 3 If power input is still not correct reset C14 again and repeat these steps until the correct reading is obtained 2 4 v for 5 watt input For receiver tuneup a simple peaking adjustment of the antenna and RF tuned circuits will usually be all that is necessary To do this use the signal level met
14. ca 68 mmf 500v 5 15421 Same as C 8 15137 Not used Same as C 8 15137 Same as C 8 15137 Same as C 8 15137 Same as C 8 15137 Same as C 8 15137 Same as C 8 15137 Same as C 8 15137 Same as C 8 15137 Same as C 8 15137 Same as C 3 15417 Ceramic 4 7 mmf 500v 1080 75 15131 Same as C 8 15137 Same as C 38 15161 Same as C 8 15137 Same as C 2 15132 Mica 150 mmf 500v 5 15418 GENERAL RADIO SERVICE EQUIPMENT REF SYMBOL 00000000000 1100009000 2 55 55 CR 1 CR 2 CR 3 DESCRIPTION Same as C 8 Same as C 64 Ceramic 001 mf 500v 10 Same as C 8 Molded mylar 47 mf 200v Same as C 32 Molded mylar 12 mf 600v Electrolytic 80 80mf 200v Part of C 69 Electrolytic 30 30 mf 350v Part of C 71 10 20 200v CONTROLS Meter zero control 50K Off on volume control 250 K Squelch Control 10K COILS RF Choke RF Coil slug tumed RF Choke RF Inductor RF Choke RF Choke AF Choke RF Input Same as L 2 IF Trans Same as L 10 Same as L 10 Same as L 2 less slug Same as L 1 Hash choke DIODES Diode Silicone rectifier Same as CR 2 CABLES AND CONNECTORS Pin jack red Pin jack black RF connector Cable W Socket 6v 19v Cable W Socket 117v AC 10 contact plug RESISTORS 47K ohms 1 2w 10 Same as R 1 4 IK ohms 1 2w 10 22K ohms 1 2w 10 Same as R 4 100 ohms 1 2w 10 3 3K ohms 1 2w 10 Page 15 PART NO 15137 15136 15136 15137 15675 1514
15. cts for AVC voltage but prevents the oscillator injection voltage from feeding back into the AVC line The IF is amplified by two IF stages V 9 and V 10 which differ only in that the gain of V 9 is AVC controlled and the gain of V 10 is fixed by the cathode resistor R 46 The detector V 6B supplies audio to the audio driver V 3A through a series gate noise limiter circuit This consists of the gating diode V 6A capacitors C 32 and C 34 and resistors R 22 1 R 22 2 R 25 and R 26 Due to the RC time constants V 6A is biased to conduct and pass audio signals for normal voice signals but stops conducting for high amplitude noise pulses of short duration The second detector also supplies AVC voltage a noise controlling voltage to modify the AVC voltage and squelch voltage The AVC system consists of R 49 and C 39 1 an RC filter with carrier signal taken from Page 3 MODEL GRS 1566 GENERAL RADIO SERVICE EQUIPMENT CIRCUIT DESCRIPTION RECEIVER Continued the secondary of L 12 Another RC filter from this point C 36 R 27 responds to short duration noise pulses only these are passed through C 35 to drive the noise amplifier V1 B The amplified noise is then rectified by V 5A and applied as a positive bias to the AVC line This arrangement keeps the receiver gain high in the presence of noise thus making it possible to receive weak signals through noise Without this arrangement such weak signals would otherwise be lost The squelc
16. erand tune L9 and L8 for maximum while receiving a weak signal The receiver IF trans former should be left alone unless there is definite evidence that the tuning is required If this is the case apply a 455 kc crystal controlled 001 signal to the mixer grid and tune L10 L11 and L12 for maximum meter reading as in con ventional receiver alignment techniques The frequency should be exactly 455 kc to avoid possible loss of some stations which may be operating near the limits of channel frequency tolerance Local broadcast stations can be used to establish check points to confirm signal generator calibration at 455 kc PARTS LOCATIONS The following is a bottom and top view photograph of the GRS 1566 The location of individual circuit components is clearly illustrated To locate a part refer first to the schematic diagram if the part in question is connected directly to a tube socket terminal it may not be identified on the photograph A detailed description of each part is listed at the end of this manual MODEL GRS 1566 V4 GAQ5 12A X7 V3 7025 KI u2 V10 6BAG u l PONT x l 3 LEA che 11 v5 Le L5 5 Page 9 VOLUME V2 6AQ5 Page 10 MODEL GRS 1566 GENERAL RADIO SERVICE EQUIPMENT SUPPRESSION REDUCING IGNITION NOISE Ignition noise is one of the prime factors limit
17. factorily without further adjustments However it is strongly recommended that a qualified service technician be called in to check the installation This will ensure optimum performance of the equipment At the same time the set can be activated on other General Radio Service channels as described in the paragraph following providing always that only crystals supplied by Chisholm Industries Limited CIL are used TUNEUP ON OTHER CHANNELS The General Radio Service is divided into 19 channels as follows Channel Frequency Channel Frequency Channel Frequency Channel Frequency 4 27 005 9 27 065 14 27 155 19 21 185 5 21 015 10 21 075 15 21 135 20 21 205 6 21 025 31 27 085 16 21 155 21 21 215 1 21 035 12 87 105 17 21 165 22 21 225 8 21 055 13 Emg 27 115 18 21 175 When one set of crystals is installed at the factory operation will occur with the channel selector switch in the position marked A Additional pairs of crystals if ordered are installed in the B C D and E positions The set will operate only on the channel or channels for which crystals are supplied Only a qualified service technician should be permitted to set up additional channels or t change channels When he installs the crystals he will check transmit fre quency and loading and make appropriate internal adjustments as required CHISHOLM GRS CHANNEL IDENTIFICATION TRANSFER 1 Select the applicable GRS channel number on the sheet Cut allowing
18. g has negligible effect except when spark plugs are badly fouled It is the general consensus that the use of spark plug and distributor suppressors does not interfere with engine performance nor increase fuel consumption To reduce the direct radiation of ignition interference suppressors can be installed on each spark plug and at the distributor These suppressors consist of a resistor encased in a tubular insulating housing with terminals on each end to fit the spark plugs or distributor to the ignition cables Instead of suppressors spark plugs which have built in resistors can be substituted or alternatively special ignition cables with built in resistance provided in many new cars can be used Series resistance in the ignition circuits has two effects It reduces the radiated field by limiting current and broadens the resonance lowers the Q of the wiring ADDITIONAL REMEDIES In addition to the high voltage ignition system electrical noise is caused by the vibrating contacts within the current voltage regulator the brushes and commutator of the generator the opening and closing of the distributor points and the charging and discharging of the distributor capacitor Cl in Fig 1 For an ordinary auto radio generator whine is adequately suppressed by installa tion of a 0 1 to 0 25 mf 100 v capacitor between the frame of the generator and the output terminal of the generator which is connected internally to a brush that co
19. h system biases off the audio driver stage V 3A whenever the received carrier amp litude is less thana given value as determined by the setting of the squelch control R 50 The squelch rectifier tube V 6C rectifies the carrier to develop a negative voltage which opposes the positive voltage from the squelch control R 50 For normal reception the total voltage is negative to ground by an amount great enough to keep the squelch control tube V 3B from conducting The audio driver tube V 3A now acts as a regular class A RC coupled amplifier with bias due to contact poten tial current through R 13 When the receiver signal is removed or the level drops below the value selected for squelching the bias for V 3B goes more positive and V 3B conducts The plate current of V 3B flows through R 14 and R 33 to B the resulting voltage drop across R 14 biases V 3A beyond cut off and the audio is removed squelched The noise amplifier rectifier system V 1B V 5A adds a positive bias to the grid of V 3B through resistor R 23 during squelched conditions causing the squelch to hold steadily under noisy conditions The audio output stage is a class A audio power amplifier with transformer coupling to the 3 2 ohm speaker For receiving the signal level meter is connected to a bridge circuit One side of the bridge consists of R 8 R 9 and R 10 The other side consists of resistors R 44 R 45 to B and the effective cathode to screen resistance of V 9 and R
20. he noise stops Rotate control slightly beyond the point where the noise drops out at this point any signals even weak ones will cause the sound to come back on again Note Very weak signals can best be received by adjusting the squelch control in a more counter clockwise direction Key transmitter by pressing microphone button Turn the power tuning control to the point where the meter reads maximum for most sets this will be between 4 and 6 on the scale Give call sign and observe all other operating procedures which are required by the Department of Transport Follow the same procedure when selecting another channel that is the squelch volume and power tuning controls may have to be reset after switching from one channel to another NOTICE TO GENERAL RADIO SERVICE BAND LICENSEES Your attention is drawn to the fact that the FULL call sign of the station must be used when calling and on sign off The call sign is shown at the top right hand corner of the licence and consists of the letters XM followed by a number The letters XM are part of the call sign and must be transmitted as such Each exchange of communications between licensed stations shall not exceed five consecutive minutes duration and upon the termination of an exchange of communi cations no further transmission shall be made until the lapse of two minutes or until interference will not be caused to other stations using the same frequency Page 8 MODEL GR
21. inder The protruding wire is for connection to the hot side of a circuit and the mounting lug of the capacitor enclosure is fastened to the generator or the regulator cover firewall or other grounded surface To be effective the lug must make firm contact with clean metal paint or grease removed or to the mounting bolt Suppressor capacitors with two leads one to ground do not have to be mounted rigidly Although these standard auto radio noise suppressors are adequate for AM broad cast band reception they may not be adequate for GRS reception This is due to the fact that standard paper capacitors possess inductance as well as capacitance This inductance has no significant effect at relatively low frequencies but may be so great at 27mc as to offset the bypassing effect of the capacitor Sufficient by passing at both broadcast band frequencies and at 27 mc can often be achieved by shunting ordinary capacitor suppressors with a 0 001 mf ceramic unit which has very low inductance An even better arrangement is to use coaxial capacitors Instead of conventional suppressor capacitors C2 of Fig 1 and C3 and C4 in Fig 2 coaxial types may be substituted A coaxial capacitor is a feedthrough type The lead to the hot primary terminal of the ignition coil for example is removed and connected to one end of the capacitor The other end is connected to the ignition coil The rase dr Sici SACRA ete te Ue 22919 Ro te
22. ing the range of GRS mobile installa tions The range would be considerably greater if the full sensitivity of receivers could be utilized but what use is it to have a receiver with one microvolt or better sensitivity if the ignition noise level is several microvolts Unfortunately the automobile ignition systems create and radiate radio frequency energy whose level is maximum at frequencies close to the 27 mc band This is bad for the GRS operator You can do something about suppressing noise generated by your own car but there is nothing you can do about stopping the noise generated by other cars You will however experience less noise from other cars if your receiver incorporates a noise limiter Sometimes the noise suppression procedures that are followed when a standard AM broadcast band auto radio is installed will suffice but not always It is common to install spark plug suppressors in all of the plugs and a suppressor in the distribu tor rotor ignition coil lead in order to reduce ignition noise Also a filter capacitor is usually installed across the armature terminal of the car s generator to reduce generator produced noise If these measures do not stop the noise coax or conven tional capacitors are also installed at the hot battery primary lead of the ignition coil the ammeter dome light and dashboard instruments to bypass to ground the ignition noise signals picked up and re radiated by the vehicle s low voltage wiring
23. ive turn on the GRS set unsquelched and listen to the noise with the engine on and the car moving Then stop the car and turn off the engine and note the difference in background noise level The most effective test is run when receiving a very weak radio signal Although effective noise suppression may take some time and trouble the results are worth the effort Page 14 MODEL GRS 1566 E 8687880158 Cl 1 25 mf 100v condensor g o C2 Part of Distributor in car d cis R1 R 8 Resistor type plugs or a n H IGNITION POINTS wire uh R9 Suppressor or radio resistor 9 amp wire ul 51 Ignition switch S 1 1 IGNITION SYSTEM CIRCUIT FOR 8 CYLINDER CAR FIG 1 REGULATOR way IR EUN RI I T 82 a Cl 1 25 mfd 100v condensor C2 Same as Cl C3 1 25 mfd 100v coax 3 Be RES condensor GENERATOR RE Ge Same ae C3 H C5 3 35 mmf compression ex R3 trimer condensor C6 Ceramic 200 mmf 400 v c2 c condensor R3 3 9 6 8 ohm 1 2 watt 20 Ll 8 terns of 10 enameled wire FIG 2 REGULATOR AND GENERATOR CIRCUIT wound on a 1 diameter form RI E2 SPARK E3 GAP 1 FIG 3 FIG 3B MODEL GRS 1566 REPLACEABLE PARTS REF SYMBOL 1 D 00 3 5 A co Ro ra agua papa papa paa 5355502022 00000000
24. n tacts the armature In Fig 2 this capacitor is shown as Cl Page 12 MODEL GRS 1566 GENERAL RADIO SERVICE EQUIPMENT ADDITIONAL REMEDIES Continued However for GRS reception this may not be adequate A parallel resonant wave trap L1 and C5 may be connected in series with the generator output lead as shown in Fig 2 With the engine running and the receiver on unsquelched C5 is adjusted for the minimum generator whine When tuned correctly L1 C5 serve as a very high impedance at the GRS operating frequency The trap is used in conjunction with Cl to cut out generator whine when using the regular auto radio The noise caused by the vibrating contacts of relays RL1 RL2 and RL3 Fig 2 of the regulator may be minimized by connecting a 0 1 to 0 25 mf 100 v capacitor C3 between the grounded cover of the regulator and its battery terminal and another capacitor C4 between the cover and the generator terminal of the regulator Filters are usually not connected to the field terminal of the generator or regulator because of possible damage to the regulator relay contacts But a circuit that is sometimes recommended for connection here is a resistor R3 with a value of 3 9 to 6 8 ohms and a series mica or ceramic capacitor C6 of around 200mmf as shown in Fig 2 between the regulator cover and its field terminal FILTER CAPACITORS Ordinarily capacitors used for noise suppression are paper types enclosed ina metal cyl
25. n three and six miles from the centre of either a land or water aerodrome i Where the antenna is to be erected on an existing structure and will not exceed 20 feet in height above that structure completion of 2022A forms will not be required ii Where the antenna structure is to be self supporting completion of 2022A forms by the applicant will be required however where such antenna structure will not exceed 75 feet in height above ground level and will not exceed 20 feet in height above any terrain features or existing structures within a radius of 1 000 feet forms 2022A will not be required c Beyond six miles from the centre of a land or water aerodrome i Where the antenna is to be erected on an existing structure and will not exceed 30 feet in height above that structure 2022A forms will not be required ii Where the antenna structure is to be self supporting completion of 2022A forms by the applicant will be required except where such antenna structure will not exceed 75 feet in height above ground level and will not exceed 30 feet in height above any terrain features or existing structure within a radius of 1 000 feet forms 2022A will not be required Page 5 MODEL GRS 1566 GENERAL RADIO SERVICE EQUIPMENT INSTALLATION PROCEDURE When the crystals are installed the unit is pre tuned and ready to operate when ground antenna and power connections are made BASE STATION 1 Connect ground terminal to wa
26. nd through the push to talk switch on the micro phone When receiving the microphone switch is up permitting the relay contacts to energize the receiver as follows K 1A connects the antenna to the receiver K 1C applies DC to all stages of the receiver and K 1B grounds the speaker to place it in operation The audio driver and the output stages are supplied with DC con tinuously since they are used for both transmitting and receiving When the microphone push to talk switch is pressed K 1 closes and its contacts place the transmitter on the air as follows K 1A transfers the antenna to the transmitter output K 1C applies DC to the transmitter oscillator V 1A K 1B grounds the cathodes of both the oscillator and power amplifier and K 1D applies modulated DC to the power amplifier to place the transmitter carrier on the air CIRCUIT DESCRIPTION RECEIVER The receiver is a XTAL controlled superheterodyne with squelch automatic noise limiting and noise controlled AVC circuits all included to give superior reception properties The incoming signal is amplified by V 7 the RF amplifier and applied to the mixer grid V 8A A signal 455 kc higher than the channel frequency is coupled to the grid from oscillator section V 8B an independent triode in the same envelope The oscillator is a Colpitts circuit with frequency doubling in the plate circuit The mixer grid is AVC controlled through V 5B the mixer AVC gate diode This diode condu
27. pacitor and the signal level meter reads the rectified voltage The modulating signal for the transmitter is obtained through V 3A and V 4 These stages serve as the audio driver and the modulator stages respectively while transmitting Page 4 MODEL GRS 1566 GENERAL RADIO SERVICE EQUIPMENT CIRCUIT DESCRIPTION TRANSMITTER Continued The audio from the microphone is fed through the cold end of the volume control amplified by V 3A a class A resistance coupled audio voltage amplifier and again by V 4 a class A audio power amplifier The speaker is disconnected while trans mitting due to K 1B The primary of T 1 acts as a choke across which the audio modulating voltage is developed This in turn modulates the plate and screen voltage of the RF power amplifier stage in what is commonly referred to as a choke coupled or Heising modulation system ANTENNA The GRS 1566 Radiophone is designed and tuned for operation into a 52 ohm antenna The following information is reprinted from Radio Standards Specification 136 Issue 1 ANTENNA STRUCTURE REQUIREMENTS FOR LAND STATIONS IN THE GENERAL RADIO SERVICE Where a land station antenna structure is to be erected such structure shall be sub ject to prior Department of Transport approval on the following basis a When within three miles of the centre of either a land or water aerodrome Department of Transport form 2022A shall be completed by the applicant b When betwee
28. ter pipe or other good ground 2 Install antenna according to instructions furnished In general the antenna should be located in the clear and as high as possible 3 Plug in antenna and AC power cord the set is now ready for operation VEHICULAR INSTALLATION 1 Install mounting hood under the dash or other convenient location Note that DC primary cable supplied with the set may have to be lengthened if the unit is mounted elsewhere 2 Connect the ground side of the DC primary cable to a cleaned metal spot on vehicle chassis Bolt securely 3 Connect hot side of primary cable wire with in line fuse to ignition switch or accessory binding post in vehicle For normal installation this should be a post which is switched on and off by the ignition key 4 Install antenna according to instructions furnished 5 Install set on mounting hood and tighten in place Insert antenna and power cord plugs the set is now ready for operation With the radiophone in operation start up the vehicle engine and listen for ignition noise Excessive ignition noise will seriously impair weak signal reception Refer to Ignition Suppression Section HOW TO ASSEMBLE ANTENNA CONNECTOR to coaxial RG58 U lead in cable Cut end of cable even Remove vinyl jacket 3 4 Slide coupling ring part of 83 1SP adapter 83 185 on cable Fan braid slightly and fold back as shown Position adapter to dimension shown Press braid down over body of
29. w OONN 1 Part No 74072 Printed in Canada Page 2 CHISHOLM INDUSTRIES LIMITED MODEL GRS 1566 GENERAL RADIO SERVICE EQUIPMENT DESCRIPTION POWER SUPPLY AND CONTROL CIRCUITS Power input can be 117 volts AC 12 volts DC or with a minor circuit modification 6 volts DC For 117 volt AC operation the AC cable is connected to the power re ceptacle for 6 or 12 volt DC operation the DC cable is plugged into the power receptacle When operating on 117 volts AC the line voltage is stepped up by one winding of transformer T 2 and converted to DC Another winding of T 2 steps down the 117 volts to a value suitable for use by the heaters of all tubes When operating with 6 or 12 volts DC the DC cable automatically switches the unit to DC operation and the appropriate voltage is applied to the heaters of all tubes Vibrator VIB 1 converts the steady state DC to a pulsating DC The pulsating DC is applied to a winding on transformer T 2 and the stepped up voltage appearing at the secon dary winding of T 2 is converted to DC by the rectifiers CR 2 and CR 3 and capacitors 5 69 and C 70 forming a voltage doubler circuit Resistors R 55 R 56 and capacitors C 71 C 72 filter the varying DC output of the voltage doubler The DC output is applied directly to the audio driver and output stages V 3 and V 4 and via resistor R 16 to the coil of the keying relay 6 1 The coil of the keying relay is actuated by grounding the low e
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