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Author Topic: SYNCHRONIZATION: SYNC. WHAT IS IT?  (Read 6380 times)
K0YNE
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« on: May 21, 2009, 10:10:23 PM »

 Smiley I HAVE OVERHEAD QSO'S AND SYNC BEING MENTIONED. SYNCHRONIZATION IS A PART OF THE DIGITAL MODES AND SSTV BEING ONE OF THEM. SYNCHRONIZING SIGNALS ON THE TRANSMIT END
TO THE SYNCHRONIZING PULSES BEING GENERATED ON THE RECEIVING END MAKES THE OLD ANALOG
TELEVISION RUN SMOOTHLY AND ALLOWS TROUBLE FREE TRANSMISSIONS.
IN COLOR ANALOG  TELEVISION, 3 BASIC SYNC SIGNALS ARE SENT IN THE TRANSMISSION.
TWO OF THE SYNC SIGNALS ARE THOSE FOUND IN THE SWEEP PART OF THE TRANSMISSION. A VERTICAL SYNC SIGNAL AND A HORIZONTAL SYNC SIGNAL. IN ORDER FOR THE ANALOG SIGNAL TO BE
REPRODUCED, AND SEEN WITHOUT ROLLING UP OR DOWN, A SYNC PULSE IS GENERATED
AND SENT. THE VERTICAL SYNC PULSE FOR COLOR COMPATIBLE TELEVISION WENT FROM 60 HZ PER
SECOND TO 59.94 PER SECOND. THESE PULSES ARE PRESENT WITH THE OUTGOING COMPOSITE
VIDEO PICTURE INFORMATION.  WHEN THE COMPOSITE SIGNAL IS RECEIVED, THE VERTICAL PULSES
ARE SEPARATED AND CHANNELED TO A VERTICAL CIRCUIT THAT USES THESE "PERFECT" PULSES TO
GUIDE THE "INTERNAL VERTICAL SYNC PULSES" SO THE TWO SIGNALS WILL BE IN TIME WITH EACH
OTHER. IF FOR EXAMPLE , THE INTERNAL TV'S SYNC GENERATOR WAS OFF A BIT, YOU WOULD
EXPERIENCE A VERTICAL ROLL TO THE PICTURE EITHER GOING UP OR DOWN DEPENDING WHICH WAY
THE GENERATOR WAS OFF EITHER TOO HIGH OR TOO LOW. ONCE THEY BECOME SYNCHRONIZED, THE
PICTURE REMAINS STABLE.  MODERN DAY SYNC CIRCUITS ARE MUCH MORE SOPHISTOCATED AND NEVER SEEM TO SHOW ANY INSTABILITY.

NEXT IS THE HORIZONTAL SYNCHRONIZATION. A HORIZONTAL PULSE IS ALSO GENERATED LIKE THE
VERTICAL SYNC PULSE WAS AND RUNS AT A HIGHER FREQUENCY. IN TODAYS COMPOSITE VIDEO WHICH
IS ALSO COLOR COMPATIBLE, THE FREQUENCY IS 15,734.5 HZ PER SECOND. BEFORE RCA INTRODUCED COMPATIBLE COLOR, THE BLACK AND WHITE STANDARD WAS 15,750 HZ PER SECOND. WHEN COMPATIBLE COLOR WAS ADDED, IT ALLOWED NO CHANGES NECESSARY TO EXISTING TV SETS ACROSS THE COUNTRY AND AROUND THE WORLD. BY INSERTING COLOR, REQUIRED A FINE TOUCH UP OF BOTH THE VERTICAL AND THE HORIZONTAL FREQUENCIES TIMING. BOTH HAD TO BE REDUCED ENOUGH TO ALLOW FOR THE TV'S COLOR SYNC SIGNAL TO BE ADDED. THE COLOR INFORMATION AND COLOR SYNC
NOW COULD BE ADDED AND  ALLOWING OLDER SETS TO OPERATE NORMALLY.
WHEN THE SYNC SIGNAL WAS SENT AT 15,734.5 HZ PER SECOND, FROM THE CAMERAS, THE SIGNAL IS AGAIN SEPARATED WITH IN THE TV'S RECEIVER AND SENT TO
THE HORIZONTAL SYNC DETECTOR AND THE DETECTOR IN STEP WITH THE HORIZONTAL SYNC PULSE
GENERATOR , FALL INTO STEP WITH EACH OTHER, GIVING THE PICTURE STABILITY AND ELIMINATES
HORIZONTAL LINES AND SIDE STEPPING.. NOW THAT WE HAVE BOTH VERTICAL STABLITY AND HORIZONTAL STABILITY, OUR PICTURE SHOULD LOOK GOOD/

NOW COMES THE 3RD SYNC PULSE SIGNAL. IT IS COLOR.  IN THE TELEVISION STATION, A MASTER
GENERATOR IS GUIDING ALL CAMERAS AND VCR'S AND OTHER PLAYBACK EQUIPMENT. THE MASTER GENERATOR KEEPS ALL IN STEP AS A DRILL INSTRUCTOR IN THE ARMY WOULD
KEEP ALL THE TROOPS IN STEP.
WHEN A COLOR CAMERA  IS DISPLAYING A TRUE SPECTRUM OF COLORS, ITS INTERNAL
COLOR PHASE CONTROL IS PRECISELY SET TO PRODUCE A CORRECT COLOR PHASE OUTPUT ALLOWING
THE OUTGOING SIGNAL TO BE RECEIVED CORRECTLY. WHEN THE TV'S RECEIVER PICKS UP THE VIDEO
INFORMATION, THE COLOR SIGNAL IS SAMPLED AND SENT TO THE COLOR PHASE DETECTOR. INFORMATION
SENT IS NOW DETECTED AND SENT TO VARIOUS COLOR AMP STAGES AND FINALLY TO THE CRT OR THE COLOR PICTURE TUBE. SINCE MOST TV'S STILL HAVE A COLOR SATURATION ADJUSTMENT FOR MORE OR LESS COLOR, AND A HUE ADJUSTMENT TO CORRECT THE COLOR PHASE TO BRING IT INTO PHASE WITH WHAT THE STATION HAD SENT. IN GENERAL A COLOR CRYSTAL OF 3.58MHZ IS INSTALLED IN THE TELEVISION AS A EXACT STABLIZING CIRCUIT. SOME TELEVISION SETS WOULD RECEIVE THE COLOR SYNC PULSE AND THEN IT WOULD "RING" THE CRYSTAL FOR ONE LINE OF VIDEO. THE RINGING WOULD
BE LONG ENOUGH TO COMPLETE ONE LINE. OTHER CIRCUITS WOULD GIVE A MORE SUSTAINED SYNC PULSE.  
THE COLOR BURST IS LOCATED ON THE BACK PORCH OF THE HORIZONTAL SYNC PULSE HAVING AT LEAST
8 OR MORE CYCLES OF COLOR BURST AT 3.58MHZ.
IN THE ANALOG SSTV CIRCUIT, WHEN RECEIVING AND SENDING , YOU WILL HEAR THE SYNC PULSE. THE RECEIVING STATION , WILL GET THE PULSE, AND THE PROGRAM WILL COUNT THE PULSES TO DETERMINE WHICH SLOW SCAN MODE WAS USED? WAS IT SCOTTIE 1 OR SCOTTIE 2.?


WELL, IF THIS IS CONFUSING, YOU WON'T BE ALONE. BUT SYNC IS NECESSARY AND AS IN SENDING
FAX MESSAGES, THE MACHINES MUST KNOW WHEN TO BEGIN A LINE AND END A LINE.

HOPE THIS IS HELPFU.   PAUL K0YNE
« Last Edit: October 22, 2009, 11:32:22 AM by K0YNE » Logged
K0YNE
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« Reply #1 on: May 22, 2009, 02:38:12 PM »

I MIGHT ADD THAT IN THE ADVENT OF COLOR TELEVISION, RCA'S MOST UNIQUE AND PROFOUND TECHNOLOGY ADDED AND CALLED COMPATIBLE COLOR IN THE EARLY 50'S, WAS ONE OF THE MAJOR
INNOVATIONS IN ELECTRONICS IN THE PAST CENTURY. YOU MAY READ LITTLE ABOUT THIS, AND NOT
MUCH PUBLISHED ON THIS TECHNOLOGY, BUT REMAINS TO THIS DAY AN ADAPTATION TO ALLOW
EXISTING BLACK AND WHITE TELEVISIONS TO BE VIRTUALLY UNAFFECTED BY THE ADDED COLOR
PROGRAMMING BEING SENT SIMULTANIOUSLY.  PAUL  K0YNE
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