[time-nuts] from Sputnik to TV

[Tom Van Baak]

> a related very interesting experiment is to take the Horizontal Sync signal  
> from an old Tube-type TV, and feed it to a frequency counter with GPSDO time  
> base (preferrably).
> 
> Got to be careful about the high voltages inside the TV though!

If you use proximity EM field pickup you don't even have to
be careful. That's how some of the amateur TV frequency
standard projects worked.

> BTW: it's not 15374KHz, there are some significant decimal digits (I don't  
> recall the formula to calculate the frequency exactly, but it was the total  
> number of frame lines multiplied by 59.94Hz or so).

You can see why, in the pre-GPS 1970's, color television carriers
were useful as lab frequency standards. Sample NIST papers:

Precision and Accuracy of Remote Synchronization Via
Portable Clocks, Loran-C, and Network Television Broadcasts 
http://tf.nist.gov/timefreq/general/pdf/760.pdf

Nationwide Precise Time and Frequency Distribution Utilizing
an Active Code Within Network Television Broadcasts 
http://tf.nist.gov/timefreq/general/pdf/1601.pdf

Long-Term Continental U.S. Timing System Via Television Networks 
http://tf.nist.gov/timefreq/general/pdf/237.pdf


Exact numbers for NTSC color television are:

subcarrier, Fsc = 5 MHz x 63 / 88 = 3 579 545.454 Hz (~3.58 MHz)

line rate, Fh = Fsc / 455 = 15734.265 Hz
  note 455 = 5 x 7 x 13

field rate, Fv = Fh / 525 / 2 = 59.940 059 Hz
  note 525 = 3 x 5 x 5 x 7

Equivalently:

Fv = 60 Hz x 1000 / 1001 = 59.940 059 Hz
  note 1001 = 7 x 11 x 13

Fh = 4.5 MHz / 286 = 15734.265 Hz
  note 286 = 2 x 11 x 13

Fsc = Fh x 455 / 2 = 3 579 545.454 Hz 
  note 455 = 5 x 7 x 13


For those of you who like prime numbers, number theory, tube
multivibrators, in addition to being a time nut (or does that narrow
it down to just me?), my favorite TV time/frequency article is:

A Tutorial on Magic Numbers for High Definition Electronic Production
http://www.poynton.com/PDFs/Magic_Numbers.pdf


For a less mathematical treatment see:

http://en.wikipedia.org/wiki/NTSC
http://www.edlmax.com/AudioNTSC.htm
http://stjarnhimlen.se/tv/tv.html#FRAMERATE
http://www.theiabm.net/Technology.aspx?i=10
http://www.goupi.org/analogtv.html
http://www.quantel.com/site/en.nsf/html/library_dfb
  to download the Quantel Digital Factbook in PDF format

/tvb
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