Moseley Associates SCG-3T Instruction Manual Download | Manualshive

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Summary of Contents for SCG-3T

Page 1: ...www SteamPoweredRadio Com MODEL SCG 3T STEREOPHONIC GENERATOR ...

Page 2: ...oweredRadio Com I I I I I I I I le I I I I I I I I INSTRUCTION MANUAL MODEL SCG 3T STEREOPHONIC GENERATOR MOSELEY ASSOCIATES INC Santa Barbara Research Park 111 Castilian Drive Goleta California 93017 August 1970 ...

Page 3: ...I TABLE OF CONTENTS I I Page I Introduction l I II Specifications 2 I III Installation 3 IV Principles of Oper ation 4 I V Detailed Circuit Description 5 I VI Adjustment 9 VII Operational Suggestions 11 le I I I I I I I SCG 3T 1 I ...

Page 4: ...signed to greatly exceed the system require ments in every respect Considerable degradation may occur in other portions of the system before performance fails to come up to FCC standards as set forth in Section 73 322 of the R ules Aside from superior electronic operation the SCG 3T also fea tures built in metering of the audio and output signals small size rugged construction and pushbutton mono ...

Page 5: ...lat Less than 0 4 stereo or mono Better than 68 dB below normal output 3 5 volts peak to peak 5 volts maximum 5ooon l 000 picofarads Less than l Hz drift in 6 months 35 dB minimum 45 dB typical 43 dB minimum SO dB typical in cluding the built in 17 kHz low pass program filters 48 dB minimum 55 dB typical with or without modulation Better than 60 dB below normal output Front Panel illuminated pushb...

Page 6: ...dio p r ocessing device several of which are available on the market The remote control lines for selecting stereo or monaural operation should be connected to a pair of pushbuttons single pole single throw normally open Each button returns to ground If a two conductor plus shield can be used as the ground connection These remote buttons can be used fo switch from the stereo mode to mono and back ...

Page 7: ...hat he re creates the original left and right channels It has been deter mined in practice that this scheme is compatible with other services such as simultaneous background music transmission In addition to switching the output signal alternately between the left and right audio channels a pilot tone signal is also trans mitted to enable the receiver to synthesize a switching signal to decode or ...

Page 8: ...l from the electronic or one of the audio channels to the output amplifier 5 A metering system 6 A power supply DETAILED CIRCUIT DESCRIPTION The following description is with reference to the block diagram shown in drawing number 92A l 004 Discussing first the switching signal generation process observe the 76 kHz crystal controlled oscillator using IC 301 in the upper left corner of the block dia...

Page 9: ...hannel has th e variable controls for matching Discussing the left channel first this amplifier has a very large amount of negative feedback applied to it This reduces distor tion and stabilizes the gain and other characteristics More important it allows the use of resistors and capacitors to achieve an accurate pre emphasis characteristic To increase the power handling ability of this amplifier i...

Page 10: ...the Main 11 sum 11 or LtR11 signals These are all one and the same Likewise the difference ster eophonic subcarrier 11 subchannel and L R signals are all one and the same In a similar manner if the left and right channels are fed from the same source but of opposite polarity then the resultant main channel output from the stereo generator must be suppressed by the same amount 40 dB This can be acc...

Page 11: ...d bandwidth to give a good indication not only with monaural operation but also with stereo operation The output stage of this amplifier has the current handling ability to enable the peak detector to respond to very short pulses of signal i e stereo waveforms The am plifier deliveres its signal to the meter located on the power supply module This meter is peak reading and is calibrated in decibel...

Page 12: ...y Description of the various internal controls and their functions will enable the competent engineer to quickly correct minor discrepancies possibly without loss of air time Some tests require momentary removal of program but in any event the unique packaging of the SCG 3T enables fast access to the circuitry from the front of the rack while maintaining a clean front panel appearance The location...

Page 13: ...tion the modu lation percentage is equal This control is adjusted to make the mono agree with the previously adjusted stereo signal level 50 HZ GAIN This control affects the gain of one of the audio channels at low frequencies only It is necessary for the two channels to have identical gain at all frequen cies in order to have minimum cross talk Feeding both channels in phase with a low frequency ...

Page 14: ...fficient at room temperature No other com ponents significantly affect frequency At the right rear of the main stereo board will be noted the output buffer amplifier using IC 307 This is a direct coupled amplifier with a few external components for phase compensation and parasitic suppression There may also be seen a few blank holes in this area These are for the purpose of pre distortion of the s...

Page 15: ... in the stereo receiver when SCA signals are being transmitted on 67 kHz along with the stereophonic progranuning This whistle at a frequency of 10 kHz is generated in the stereo demodulator as a byproduct of the demodulation process The 19 kHz pilot tone itself is demodulated 11 and a large third harmonic component is developed This 57 kHz signal which is not transmitted but which is gener ated i...

Page 16: ...adjustments made to it to give correct readings Generally speaking such adjustments can be confirmed as being erroneous by carefully running through the entire setup procedure for the stereo generator Sume moni tors can be checked out in the field without external equipment while some require more test equipment The most valuable single piece of equipment the broadcaster c an use to visually check...

Page 17: ...__ Pilot Injection 9 0 Signal to Noise Ratio D emodulated Left 68 db Demodulated Right 68 db Input Level for 100 Mod 100 Hz 10 5 dbm Separation Hz L into R R into L 50 45 42 400 48 42 1000 46 43 5000 44 41 10000 42 40 15000 36 36 COMMENTS 7 70 Moseley Associates Inc ml 38 kHz Carrier Suppression 63 db with no mod 60 db with 100 10 kHz Distortion 400 Hz O 18 Mono Left 0 20 Stereo L 0 21 Stereo R Cr...

Page 18: ...A I Gl 4T 3 lii QUAL LEr T 2 4 L R O F I o 5 OPPOS ITE L A NOT S MOSELEY A880CIATE8 INO u INTEANAL I MPEDANCE OF AUDIO 0SC SHOULD BEL 600 St 2 LOAD IMPEDANCE SHOULD BE 600 n RESISTIVE 3 600 n RESISTORS 270 330 1 BRIDGED 4 45 MH INDUCTOR MAY BE U TC A DuUSTABLE TOROID SANTA BARBARA CALI FO RN IA SCHEMAT C STEREO TEST FIXT URE TOL F I 32 XX 030 XXX 0 0 OWN JAG 8 69 SCALE CHI ENG 9 lA 6372 ...

Page 19: ...K L n A DJUSTMENT S A UDI O I ll J C305 f AM I I o I l J V _ I PO W ER 5U P PLY QIOl Q I 02 1 15V sv L K 1 l i V J P A S F l L R blJ Lr Q 305 N Pl 5 t I _ _I c 1e Ft l Q TOTAL R METER SWITCH METER I N C I Ill AMP t1UF F I h 6 r U f i 4 DIODE 5WIT C H CR C _ 4 CH 3 t 5 C R i G 51 ERl O MON O CARA I E R E A Ne SEPARATION BU l F E R I C 30 o f ll NE LOW PA SS F I LT ER STE R E O 516 N AL JX M NO B U ...

Page 20: ...ET ER i BO 51 55 13 0 2C B 20 3 Lt FT YEL ISE PA 6 Q35 7RAT I O R3 59 I s r Nob A 3 o0 CARil ER BALA MC ED i l6H T O R6 BUff R tNPUT nLU v o 7 K IZ V El 5WITCH C RN 3 8 G N 3t KHz Rill 6 RN RECT OUT Rc O b CR6 ll l 1P IN R 2O7 R2 0 YEL R226 AMP OUT UNFILTl REd STER EO P 3 31 P I LCT b L EVE L L3 0 1 PILOT PHASE I S Kl lZ 8 L U g l 1v1 i r MOSELEY ASSO CIATE S INC SANTA BARBARA C ALIFORN IA lu s CO...

Page 21: ...R 51 B51 2 9 VNL 5S OTHERWISE PEC ll IED R Sl TOR VALU 5 ARE IN OHMS 1 2 W o C APAC lrOR VALUES AR I IN MICRO F ARADS c J DENOTli S IN 15 4 DIODE T ST POINT JOHN50N 105 850 SRN 0 c 3 9 rlM f ov 00 I ll _ rJ 10 s 7 8 1 I ij C30S I 0 7 Ril 3 2200 R357 IOO I _______ R359 II R360 I L K ___ __ B V 0 0 i 0 if 0 0 I R323 IK 0 0 V L30 I OAI ff NOA t n e 1 MOSELEY ASSOCIATES INC SANTA aAR8ARA CAL IP ORNIA ...

Page 22: ... AR IN MlC RO ARAO 3 DE NOTE 5 TEST POINT JOW SON it lOS 850 s HEMATIC IC 271 Nl XT A 5EMSLY 21C 150 0 0 0 0 0 0 0 0 O O 0 0 CR203 0 2 0 0 0 0 O O O O 0 GRN Q 1 11 _7_ _ 0 O_v_ f ORG ij ID 0 0 O O 0 0 0 R208 B IOI _____ R2 07 L ___IO ____ J ___ Jg R t O 6 g IO K ______ COM PON ENT LAYOUT METERlt J BD 51B5130 G 3T TOL FRACT 1 32 XX 030 XXX 010 OWN F XY 7 8 SCALE FULL CHK ENG 2 0 B 2083 A ...

Page 23: ...V _____ 9 ____ _ _y _ I C R THRU C Rie RI ZOO OR MORe P l V 500 MA OR MORE 2 T IA PL T PRIMARY FOR 117 240 VOL T OP eR b i ION VNl S OTHER Wl E 5PeC F E0 RE515 TOR ALUE S AR N O MM5 1 2 WATT 010 CAPAC TOR VALUE S I ARE IN M C ROFAR A DS j I I I I I I I I I I I I I I I I I I I I I I I I I r I t I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I l I I I I I l I I I I I...

Page 24: ...MT T P 6 oR R3 4R o I 7 1 4 W 17 K z L P F 2 lc 76 6V P P ________ R ME TERING BOARD 185130 2 062083 16 CAL R22 5 47K 3 2V 0 DB IGV NO SIG REC T OUT R 2 Z Rc 27 IOOK K2 0I R337 R R 33 oo l JKHtAl J R20S IOK QZ 01 2 N 053 GRN 2 00 ZERO ADJ 9 1 5 8 14 Rcc3 IOK c2oe 10D2 01 5KHt Ar R332R 660 R205R RED IOT P CR 07 IZCIOTIO CR30e IZ CIOTIO 8LU IOT P 7 RED I IS T P I 17 BLU I 15 T r I I __J OPT 4 TII IM...

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