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[time-freq] Analog TVRO & color burst

Owen, Michael Michael.Owen at Sensis.com
Fri Mar 17 18:47:29 UTC 2006

Hi, John -

Don't ya just hate it when that happens?  :)


Michael R. Owen, Ph.D.
Senior System Engineer
Sensis Corporation 

|-----Original Message-----
|From: time-freq-bounces at lists.tapr.org 
|[mailto:time-freq-bounces at lists.tapr.org] On Behalf Of John 
|Ackermann N8UR
|Sent: Friday, March 17, 2006 11:23 AM
|To: TAPR time and frequency projects
|Subject: Re: [time-freq] Analog TVRO & color burst
|Please ignore my message below... I completely missed that you were 
|talking about TVRO, and gave you information you already have.
|I do suspect, though, that the network feeds aren't paying any 
|particular attention to long-term stability.
|John Ackermann N8UR wrote:
|> Owen, Michael wrote:
|>> Friends,
|>> Does anyone on the list know about stability of the color burst 
|>> frequency in analog TVRO signals?  A local TV station's engineer 
|>> tells me that it is good to a few nanoseconds per day.  I'm looking 
|>> for corroboration before heading out on a goose chase.
|>> I already know that terrestrial signals aren't reliable 
|because local 
|>> TV stations generate their own color burst signal from 
|>> time base.  I'm wondering about the quality of network 
|feeds through 
|>> geostationary satellites.
|>> I'm asking on this forum because REFLOCK II might be a good way to 
|>> lock an OCXO to the color burst.
|> There was a time (70s and 80s) when the colorburst and 
|horizontal sync
|> was reliable as a time source; the networks had Rb standards 
|at their 
|> distribution centers.  The NBS monitored network affiliates and 
|> published offsets from USFS.
|> The problem is that when digital video started to be used, the local
|> stations ended up resyncing everything and traceability back to the 
|> networks was lost.  So, today you can't use the TV signal 
|for frequency 
|> calibration.
|> You could still lock to the signal, but you're at the mercy of 
|> whatever
|> master sync source they're using (and if the stations I've 
|visited are 
|> any indication, it ain't atomic).  There may also be 
|discontinuities in 
|> the digital switching; I'm not sure about that.
|> John
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