IIRC there are very accurate signals in your basic color TV off theair signal. Now the question is it the 3.58 MHz color subcarrier oris it the 3.545... color burst? What about the 4.5MHz soundsubcarrier? And how accurate are they?Any info appreciated.

pretty good, I assume NTSC is similar, but if your video comesvia digital and gets converted to composite video in the STB, all betsmay be off. And the way analogue Txs are being shut down in favour ofdigital.....Have a browse at SMPTE, they may even have the specs for freemartin

frequency standard from color TV signal?

Apr 17, 2007 26 Replies

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rebel 19 years ago

My version was actually a rework of a TV-derived unit I had built earlier, which used 7812.5 Hz as the ref from the 10MHz xtal (half PAL line). Replaced the divider chain and threw out the sync separator in favour of the 10k from the Jupiter, and it ran straight off. It was only later I saw Miller's unit, and learned that I had reinvented yet another wheel.

They (Jupiters) pop up from time to time on ebay.

Since the Rockwell->Conexant->Navman transfer, the Navman people have gone Sirf and lost the 10k in the process.

There's a fair bit of doco out there on "Jupiter GPS".

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Tam/WB2TT 19 years ago

Put this together with what Tom says, and you can get 3.579545454 * 88 / 315 =1 MHz, exactly. At one time it was claimed that on live network programs the frequency accuracy of the color burst was on the order of 10E-11. What you do is to divide the color burst frequency by 315, and then multiply it by 88 in a 1 MHz crystal controlled phase locked loop. Only problem with this is that it is goiung away in 2009.

Tam

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Michael A. Terrell 19 years ago

I'm familiar with the frequency conversion but as a former NTSC TV broadcast engineer, I've seen a framestore at every transmitter site since the late '80s. That reduces your accuracy to roughly 10 MHz, +/-

27.93 Hz.

Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida

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Tam/WB2TT 19 years ago

I can't remember exactly, but I think the article I was referring to was probably from the early or mid 80s. So much for progress.

Tam

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Michael A. Terrell 19 years ago

The color burst was never intended to be used as an external frequency standard. OTOH, the framestore/proc amp cleaned and stabilized the video before transmission, and did improve picture quality.

Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida

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joseph2k 19 years ago

1 pps may well be way to slow to be useful. Sure it will eventually get there, maybe in days. Only 86,400 ticks in a whole 24 hour day. Sure you can use deltas etc., but the result "real"?

JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller

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Gary Tait 19 years ago

Richard Henry wrote in news:1176828772.265733.52460 @b75g2000hsg.googlegroups.com:

That is if you want accurate clock time.

For just an accurate frequency reference, you only need receive a signal soerced from a cesium beam reference

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