[Premium-Rx] Time Signal Station Receivers sought

[John]

Hi Ed & group,

These days, networks are genlocked (synchronized) to master time/frequency 
systems -- I've seen rubidium and GPS - disciplined systems.  This stuff has 
become so inexpensive these days, that even local stations can go with GPS 
locked systems.  Sync generators are so accurate that many stations just run 
a master sync generator for their in-house use, and have frame synchronizers 
(retiming systems) on incoming lines such as network feeds, so that the 
network is forced (call it finessed) into time with the local station. 
Because of this retiming, it is no longer accurate to assume that frequency 
is "network-accurate" when airing a network show.  The signals are, however, 
extremely accurate.

You can indeed, develop a good frequency reference from the 3.58MHz (4.43MHz 
in Europe) color subcarrier frequency...most broadcast systems use a lockup 
at 4 x 3.58MHz.  Watch out, though...good old noise enters the equation for 
us at home...we're watching off air or off cable (worse yet) which has 
noise, atmospheric flutter, multipath fading, etc.   So we have to deal with 
jitter and phase noise on the signal that would purport to be our reference. 
It's simply way easier an more trouble-free to go with GPS-disciplined 
reference equipment.

regards

John Collins
____________________________________________
----- Original Message ----- 
From: "Ed Tanton" <n4xy at earthlink.net>
To: <wb6nvh at mbay.net>; <premium-rx at ml.skirrow.org>
Sent: Sunday, January 01, 2006 11:11 AM
Subject: Re: [Premium-Rx] Time Signal Station Receivers sought


>I don't know if they still do it, but local TV stations are (were?) sync'ed 
>to network standards which are either rhubidium or cesium-based (I think 
>the former-but don't really remember.) Hence, when a local station has a 
>network show on, their frequency is pretty accurate... and so would you be. 
>Thinking about it, I believe a simple MM5369 (after all, they did use color 
>burst xtals) would have yielded some pretty accurate timing-or use an 
>appropriate set of dividers for a similar result when combined with 
>something like a 4046 PLL to lock wit the TV station. Nothing hidden about 
>it.
>
> These days, a Rockwell model TU30-D140-221 GPS receiver capable of 
> connection to something like an Isotemp OCXO134-10 disciplined 10 Mhz OCXO 
> can achieve stabilities on the order of 1 PPB over a 5 day period... 
> making that a much easier route to stabile frequency or time... all for 
> less than $150-and a few parts (included with the <$150 on ebay) plus an 
> antenna.
>
>
> Ed Tanton
>
> website: http://www.n4xy.com
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